, since the reaction involves 2 moles of hi for every mole of h2 and i2, the fifth column shows that the ratio [ hi ] 2 / [ h2 ] [ i2 ] is constant within a mean deviation of approximately 3 %. * therefore, this ratio is the proper equilibrium - constant expression, and the average value of keq for these six runs is 50. 53. the equilibrium constant can be used to determine whether a reaction under specified conditions will go spontaneously in the forward or in the reverse direction. the ratio of product concentration to reactant concentration, identical to the equilibrium constant in form but not necessarily at equilibrium conditions, is called the reaction quotient, q : q = ( not necessarily at equilibrium ) ( 4 - 10 ) if there are too many reactant molecules present for equilibrium to exist, then the concentration terms in the denominator will make the reaction quotient, q, smaller than keq. the reaction will go forward spontaneously to make more product. however, if an experiment is set up so that the reaction quotient is greater than keq, then too many product molecules are present for equilibrium and the reverse reaction will proceed spontaneously. therefore, a comparison of the actual concentration ratio or reaction quotient with the equilibrium constant allows us to predict in which direction a reaction will go spontaneously under the given set of circumstances : q < keq ( forward reaction spontaneous ) q > keq ( reverse reaction spontaneous ) ( 4 - 11 ) q = keq ( reactants and products at equilibrium ) - these are bodenstein ' s original numbers. modern data can be much more accurate, with less deviation in keq. the mean deviation is the average of the deviations of individual calculated keq from the average keq. | if 1. 0 x 10 - 2 mole each of hydrogen and iodine gases are placed in a i - liter flask at 448°c with 2. 0 x 10 - 3 mole of hi, will more hi be produced? | the reaction quotient under these conditions is this is smaller than the equilibrium value of 50. 53 in table 4 - 1, which tells us that excess reactants are present. hence, equilibrium will not be reached until more hi has been formed. | if only 1. 0 x 10 - 3 mole each of h2 and i2 had been used, together with 2. 0 x 10 - 3 mole of hi, would more hi have been produced spontaneously? | you can verify that the reaction quotient


1. 0 x 10 - 3 mole each of h2 and i2 had been used, together with 2. 0 x 10 - 3 mole of hi, would more hi have been produced spontaneously? | you can verify that the reaction quotient is q = 4. 0. because this is less than keq, the forward reaction is still spontaneous. | if the conditions of example 7 are changed so that the hi concentration is increased to 2. 0 x 10 - 2 mole liter - 1, what happens to the reaction? | the reaction quotient now is q = 400. this is greater than keq - there are now too many product molecules and too few reactant molecules for equilibrium to exist. thus the reverse reaction occurs more rapidly than the forward reaction. equilibrium is reached only by converting some of the hi to h2 and 12, so the reverse reaction is spontaneous. | if the conditions of example 7 are changed so that the hi concentration is 7. 1 x 10 - 3 mole liter - 1, in which direction is the reaction spontaneous? | under these conditions, since q equals keq within the limits of accuracy of the data, the system as described is at equilibrium, and neither the forward nor the backward reaction is spontaneous. ( both reactions are still taking place at the molecular level, of course, but they are balanced so their net effects cancel. ) the second use for equilibrium constants is to calculate the concentrations of reactants and products that will be present at equilibrium. | if a 1 - liter flask contains 1. 0 x 10 - 3 mole each of h2 and i2 at 448°c, what amount of hi is present when the gas mixture is at equilibrium? | the keq expression is treated as an ordinary algebraic equation, and solved for the hi concentration : you can verify that in example 7 the hi concentration was less than this equilibrium value ; in example 8 it was more ; and in example 9 it was just this value. | one - tenth of a mole, 0. 10 mole, of hydrogen iodide is placed in an otherwise empty 5. 0 liter flask at 448°c. when the contents have come to equilibrium, how much hydrogen and iodine will be in the flask? | from the stoichiometry of the reaction, the concentrations of h2 and i2 must be the same. for every mole of h2 and i2 formed, 2 moles of hi must decompose. let y equal the number of moles of


0 can be solved by the quadratic formula, thus for this problem the first solution is physically impossible since it shows more h2 reacting than was originally present. the second solution is the correct answer : y = 0. 935 10 - 3 mole liter - 1. therefore, the equilibrium concentrations are units and equilibrium constants as we have seen, the square brackets around a chemical symbol, as in [ n2 ], represent concentrations, usually but not exclusively in units of moles liter - 1. concentrations expressed as moles liter - 1 are often given the special symbol c, as in cn2, the concentrations measured in these units is denoted by kc. an equilibrium constant as we have defined it thus far may itself have units. in example 1, keq is unitless since the moles2 1iter - 2 of the numerator and denominator cancel. in example 2, the units of keq are moles - 1 liter since concentration occurs to the second power in the numerator and to the third power in the denominator. in example 3 the units of keq are the inverse : moles liter - 1. the units demanded by example 4, moles1 / 2 liter - 1 / 2, may seem strange but they are perfectly respectable. | what are the units for the equilibrium constants in the four reactions of example 5? | the keq expression is treated as an ordinary algebraic equation, and solved for the hi concentration : the question of units for keq becomes important as soon as we realize that we can measure concentration in units other than moles liter - 1. the partial pressure in atmospheres is a convenient unit when dealing with gas mixtures, and the equilibrium constant then is identified by kp. since the numerical values of kp and kc in general will be different, one must be sure what the units are when using a numerical constant. | one step in the commercial synthesis of sulfuric acid is the reaction of sulfur dioxide and oxygen to make sulfur trioxide : at 1000 k, the equilibrium constant for this reaction is kp = 3. 50 atm - 1. if the total pressure in the reaction chamber is 1. 00 atm and the partial pressure of unused 02 at equilibrium is 0. 10 atm, what is the ratio of concentrations of product ( s03 ) to reactant ( s02 )? the equilibrium mixture has 0. 59 mole of s03 for every 1 mole of s02. the ideal gas law permits us to convert between atmospheres


of concentrations of product ( s03 ) to reactant ( s02 )? the equilibrium mixture has 0. 59 mole of s03 for every 1 mole of s02. the ideal gas law permits us to convert between atmospheres and moles liter - 1, and between kp and kc : pv = nrt ( 3 - 8 ) ( 4 - 12 ) in the general chemical reaction written earlier, δn ( read " delta n " ), the increase in number of moles of gas during the reaction, is n = c + d - a - b ( 4 - 13 ) the equilibrium - constant expression in terms of partial pressures is with the ideal gas law applied to each gas component, we can convert this expression to kc : ( rt ) δn = kc ( rt ) δn ( 4 - 15 ) ( do not confuse the two uses of the symbol c in equation 4 - 15 : one is for concentration in moles liter - 1 and the other for the number of moles of substance c. ) | what is the numerical value of kc for the reaction of example 14? | three moles of reactant gases are converted into only 2 moles of product, so δn = - 1. hence at 1000 k, although the numerical answers that result when different units are used may differ, the physical reality must be the same. | what is the concentration of oxygen in example 14, in moles liter - 1? solve example 14 again using kc from example 15. | three moles of reactant gases are converted into only 2 moles of product, so δn = - 1. hence at 1000 k, this is the same ration of so _ 3 to so _ 4 as was obtained when atmospheres were used. the choice is one of convenience. equilibrium involving gases with liquids or solids all the examples considered so far have involved only one physical state, a gas, and are examples of homogeneous equilibria. equilibria that involve two or more physical states ( such as a gas with a liquid or a solid ) are called hetergenous equilibria. if one or more of the reactants or products are solids or liquids, how does this affect the form of the equilibrium constant? the answer, in short, is that any pure solids or liquids that may be present at equilibrium have the same effect on the equilibrium no matter how much solid or liquid is present. the concentration of a pure solid or liquid can be considered constant, and for convenience


, in short, is that any pure solids or liquids that may be present at equilibrium have the same effect on the equilibrium no matter how much solid or liquid is present. the concentration of a pure solid or liquid can be considered constant, and for convenience all such constant terms are brought to the left side of the equation and incorporated into the equilibrium constant itself. as an example, limestone ( calcium carbonate, caco3 ), breaks down into quicklime ( calcium oxide, cao ) and carbon dioxide, co2 : the simple equilibrium - constant expression is - k ' eq = as long as any solid limestone and quicklime are in contact with the gas, their effect on the equilibrium is unchanging. hence the terms [ caco3 ] and [ cao ] remain constant and can be merged with k ' eq : - keq = k ' eq [ co2 ( g ) ] this form of the equilibrium - constant expression tells us that, at a given temperature, the concentration of carbon - dioxide gas above limestone and calcium oxide is a fixed quantity. ( this is true only as long as both solid forms are present. ) measuring concentration in units of atmospheres, we get - kp = pco2 with the experimental value 0. 236 atm at 800°c. we can see what this means experimentally by considering a cylinder to which caco, and cao have been added. the cylinder has a movable piston, as shown in figure 4 - 2. if the piston is fixed at one position, then caco3 will decompose until the pressure of co2 above the solids is 0. 236 atm ( if the temperature is 800°c ). if you try to decrease the pressure by raising the piston, then more caco3 will decompose until the pressure again rises to 0. 236 atm. conversely, if you try to increase the pressure by lowering the piston, some of the co2 gas will react with cao and become caco3 decreasing the amount of co2 gas present until the pressure once more is 0. 236 atm. the only way to increase pco2, is to raise the temperature, which increases the value of kp itself to 1 atm at 894°c and to 1. 04 atm at 900°c. an even simpler example is the vaporization of a liquid such as water : this process can be treated as a chemical reaction in a formal sense even though bonds within molecules are not made or broken. imagine that the cylinder shown in figure 4 -


room temperature, then iodine is present as deep purple crystals rather than as vapor. what then is the form of the equilibrium - constant expression, and does the equilibrium depend on the amount of iodine crystals present? | the reaction is and the equilibrium - constant expression is : as long as some i2 ( s ) crystals are present, the quantity is immaterial as far as equilibrium is concerned. | tin ( iv ) oxide reacts with carbon monoxide to form metallic tin and co2 by the reaction what is the equilibrium - constant expression? | what is the equilibrium - constant expression for the following reaction leading to liquid water? what would the expression be if the product were water vapor? if the product is h2o ( l ), the equilibrium - constant expression is if the product is h2o ( g ), the equilibrium - constant expression is the preceding example shows that as long as liquid water is present the gas - phase concentration is fixed at the vapor pressure of water at that temperature. hence the water contribution, being constant, can be lumped into keq. factors affecting equilibrium : le chatelier ' s principle equilibrium represents a balance between two opposing reactions. how sensitive is this balance to changes in the conditions of a reaction? what can be done to change the equilibrium state? these are very practical questions if, for example, one is trying to increase the yield of a useful product in a reaction. under specified conditions, the equilibrium - constant expression tells us the ratio of product to reactants when the forward and backward reactions are in balance. this equilibrium constant is not affected by changes in concentration of reactants or products. however, if products can be withdrawn continuously, then the reacting system can be kept constantly off - balance, or short of equilibrium. more reactants will be used and a continuous stream of new products will be formed. this method is useful when one product of the reaction can escape as a gas, be condensed or frozen out of a gas phase as a liquid or solid, be washed out of the gas mixture by a spray of a liquid in which it is especially soluble, or be precipitated from a gas or solution. for example, when solid lime ( cao ) and coke ( c ) are heated in an electric furnace to make calcium carbide ( cac2 ), the reaction, which at 2000 - 3000°c has an equilibrium constant of close to 1. 00, is tipped toward calcium carbide formation by the continuous removal of carbon monoxide gas. in the industrial manufacture


dissociation to hydrogen and iodine is favored much more. the hydrogen iodide - producing reaction is exothermic or heat emitting : ( if you check this figure against appendix 3, remember that this reaction involves gaseous iodine, not solid. ) if the external temperature of this reaction is lowered, the equilibrium is shifted in favor of the heat - emitting or forward reaction ; conversely, if the temperature is increased, the reverse reaction, producing h2 and i2 is favored. the equilibrium shifts so as to counteract to some extent the effect of adding heat externally ( raising the temperature ) or removing it ( lowering the temperature ). the temperature dependence of the equilibrium point is one example of a more general principle, known as le chatelier ' s principle : if an external stress is applied to a system at chemical equilibrium, then the equilibrium point will change in such a way as to counteract the effects of that stress. if the forward half of an equilibrium reaction is exothermic, then keq will decrease as the temperature increases ; if it is endothermic, keq will increase. only for a heat - absorbing reaction can the equilibrium yield of products be improved by increasing the temperature. a good way to remember this is to write the reaction explicitly with a heat term : then it is clear that adding heat, just like adding hi, shifts the reaction to the left. ( see figure 4 - 3. ) le chatelier ' s principle is true for other kinds of stress, such as pressure changes. the equilibrium constant, keq, is not altered by a pressure change at constant temperature. however, the relative amounts of reactants and products will change in a way that can be predicted from le chatelier ' s principle. the hydrogen - iodine reaction involves an equal number ( 2 ) of moles of reactants and product. therefore, if we double the pressure at constant temperature, the volume of the mixture of gases will be halved. all concentrations in moles liter - 1 will be doubled, but their ratio will be the same. in example 12, doubling the concentrations of the reactants and product does not change the equilibrium constant : - keq = - = 50. 51 thus the hydrogen - iodine equilibrium is not sensitive to pressure changes. notice that in this case keq does not have units, since the concentration units in the numerator and denominator cancel. in contrast, the dissociation of ammonia is affected by changes in pressure because the


not sensitive to pressure changes. notice that in this case keq does not have units, since the concentration units in the numerator and denominator cancel. in contrast, the dissociation of ammonia is affected by changes in pressure because the number of moles ( 2 ) of reactant does not equal the total number of moles ( 4 ) of products : the equilibrium constant for this reaction at 25°c is - keq = 2. 5 10 - 9 mole2 liter - 2 one set of equilibrium conditions is - n2 = 3. 28 10 - 3 mole liter - 1 - h2 = 2. 05 10 - 3 mole liter - 1 - nh3 = 0. 106 mole liter - 1 ( can you verify that these concentrations satisfy the equilibrium condition? ) if we now double the pressure at constant temperature, thereby halving the volume and doubling each concentration, - n2 = 6. 56 10 - 3 mole liter - 1 - h2 = 4. 10 10 - 3 mole liter - 1 - nh3 = 0. 212 mole liter - 1 the ratio of products to reactants, the reaction quotient, is no longer equal to keq : - q = 1. 0 10 - 8 mole2 liter - 2 since q is greater than keq, too many product molecules are present for equilibrium. the reverse reaction will run spontaneously, thereby forming more nh3 and decreasing the amounts of h2 and n2. consequently, part of the increased pressure is offset when the reaction shifts in the direction that lowers the total number of moles of gas present. in general, a reaction that reduces the number of moles of gas will be favored by an increase in pressure, and one that produces more gas will be disfavored. ( see figure 4 - 4. ) | if the hydrogen iodide reaction were run at a temperature at which the iodine was a solid, would an increase in pressure shift the equilibrium reaction toward more hi, or less? what would be the effect of pressure on keq? | since the reaction of 2 moles of gaseous hi now yields 1 mole of gaseous h2 and 1 mole of solid i2 the stress of increased pressure is relieved by dissociating hi to h2 and i2. however, keq will be unchanged by the pressure increase. what effect does a catalyst have on a reaction at equilibrium? none. a catalyst cannot change the value of keq, but it can increase the speed with which equilibrium is reached. this


. however, keq will be unchanged by the pressure increase. what effect does a catalyst have on a reaction at equilibrium? none. a catalyst cannot change the value of keq, but it can increase the speed with which equilibrium is reached. this is the main function of a catalyst. it can take the reaction only to the same equilibrium state that would be reached eventually without the catalyst. catalysts are useful, nevertheless. many desirable reactions, although spontaneous, occur at extremely slow rates under ordinary conditions. in automobile engines, the main smog - producing reaction involving oxides of nitrogen is ( once no is present, it reacts readily with more oxygen to make brown n02. ) at the high temperature of an automobile engine, keq for this reaction is so large that appreciable amounts of no are formed. however, at 25°c, keq = 10 - 30. ( using only the previous two bits of information and le chatelier ' s principle, predict whether the reaction as written is endothermic or exothermic. check your answer using data from appendix 3. ) the amount of no present in the atmosphere at equilibrium at 25°c should be negligible. no should decompose spontaneously to n2 and o2 as the exhaust gases cool. but any southern californian can verify that this is not what happens. both no and n02 are indeed present, because the gases of the atmosphere are not at equilibrium. the rate of decomposition of no is extremely slow, although the reaction is spontaneous. one approach to the smog problem has been to search for a catalyst for the reaction that could be housed in an exhaust system and could break down no in the exhaust gases as they cool. finding a catalyst is possible ; a practical problem arises from the gradual poisoning of the catalyst by gasoline additives, such as lead compounds. this is the reason why new cars with catalytic converters only use lead - free gasoline. a proof of the assertion that a catalyst cannot change the equilibrium constant is illustrated in figure 4 - 5. if a catalyst could shift the equilibrium point of a reacting gas mixture and produce a volume change, then this expansion and contraction could be harnessed by mechanical means and made to do work. we would have a true perpetual - motion machine that would deliver power without an energy source. from common sense and experience we know this to be impossible. this " common sense " is stated scientifically as the first law of thermodynamics, which will be discussed in chapter 15


motion machine that would deliver power without an energy source. from common sense and experience we know this to be impossible. this " common sense " is stated scientifically as the first law of thermodynamics, which will be discussed in chapter 15. a mathematician would call this a proof by contradiction : if we assume that a catalyst can alter keq, then we must assume the existence of a perpetual - motion machine. however, a perpetual - motion machine cannot exist ; therefore our initial assumption was wrong, and we must conclude that a catalyst cannot alter keq. in summary, keq is a function of temperature, but it is not a function of reactant or product concentrations, total pressure, or the presence or absence of catalysts. the relative amounts of substances at equilibrium can be changed by applying an external stress to the equilibrium mixture of reactants and products, and the change is one that will relieve this stress. this last statement, le chatelier ' s principle, enables us to predict what will happen to a reaction when external factors are changed, without having to make exact calculations. a spontaneous reaction is one that will take place, given enough time, without outside assistance. some spontaneous reactions are rapid, but time is not an element in the definition of spontaneity. a reaction can be almost infinitely slow and still be spontaneous. the net reaction that we observe is the result of competition between forward and reverse steps. if the forward process is faster, then products accumulate, and we say that the reaction is spontaneous in the forward direction. if the reverse process is faster, then reactants accumulate, and we say that the reverse reaction is the spontaneous one. if both forward and reverse processes take place at the same rate, then no net change is observed in any of the reaction components. this is the condition of chemical equilibrium. the ratio of products to reactants, each concentration term being raised to a power corresponding to the coefficient of that substance in the balanced chemical equation, is called the equilibrium constant, keq. ( see equation 4 - 8. ) it can be used to predict whether a given reaction under specified conditions will be spontaneous, and to calculate the concentrations of reactants and products at equilibrium. the reaction quotient, q, has a form that is identical with that of the equilibrium constant, keq, but q applies under nonequilibrium conditions as well. for a given set of conditions, if q is smaller than keq, the forward reaction is spontaneous ; if q is greater than keq,


that of the equilibrium constant, keq, but q applies under nonequilibrium conditions as well. for a given set of conditions, if q is smaller than keq, the forward reaction is spontaneous ; if q is greater than keq, the reverse reaction is spontaneous ; and if q = keq, the system is at equilibrium. the equilibrium constant can be used with any convenient set of concentration units : moles liter - 1, pressure in atmospheres, or others. its numerical value will depend on the units of concentration, so one must be careful to match the proper values of keq and units when solving problems. if gas concentrations are expressed in moles liter - 1, the equilibrium constant is designated by kc ; if in atmospheres, by kp. just as partial pressure of the jth component of a gas mixture is related to moles per liter by pj = cjrt, so kp and kc are related by kp = kc ( rt ) δn, in which δn is the net change in number of moles of gas during the reaction. when some of the reactants or products are pure solids or liquids, they act as infinite reservoirs of material as long as some solid or liquid is left. their effect on equilibrium depends only on their presence, not on how much of the solid or liquid is present. their effective concentrations are constant, and can be incorporated into keq. in practice, this simply means omitting concentration terms for pure solids and liquids from the equilibrium - constant expression. evaporation of a liquid can be treated formally as a chemical reaction with the liquid as reactant and vapor as product. these conventions for writing concentration terms for a liquid permit us to write the equilibrium constant for evaporation as kp = pj where pj is the equilibrium vapor pressure of substance j. le chatelier ' s principle states that if stress is applied to a system at equilibrium the amounts of reactants and products will shift in such a manner as to minimize the stress. this means that for a heat - absorbing, or endothermic, reaction, keq increases as the temperature is increased, since carrying out more of the reaction is a way of absorbing some of the added heat. similarly, cooling increases keq for a heat - emitting or exothermic reaction. although the equilibrium constant keq is independent of pressure, and changing the total pressure on a reacting system does not alter keq directly, an increase in pressure does cause the reaction to shift in


wikijunior : how things work / flush toilet who invented it? flush toilets were first used in parts of india and pakistan about 2, 700 years ago. the cities of harappa and mohenjo - daro had a flush toilet in almost every house, attached to a sophisticated sewage system. remains of sewage systems have been found in the houses of the minoan cities of crete and santorini in greece. there were also toilets in ancient egypt, persia and china. in roman civilization, toilets were sometimes part of public bath houses where men and women were together in mixed company. toilets are usually connected to a septic tank, or to a sewer. in 1775 alexander cummings invented the s - trap, which is still used today, that used standing water to seal the outlet of the bowl, preventing the escape of foul air from the sewer. his design had a sliding valve in the bowl outlet above the trap. the flush toilet is sometimes called a water closet. how does it get power? a toilet works because of gravity. when a flush lever is pulled, a plug will open, allowing water to flow out to fill the basin. when the basin is full enough, gravity causes the liquid to flow out through a bend in the pipe, called an s trap. how does it work? a flush toilet disposes of our waste products by using water to send them through a drainpipe to another location. it is sometimes called a water closet, or wc. the picture below shows a typical toilet. the toilet bowl usually has a ring - shaped seat on top, which is covered by the lid when not in use. the handle, or sometimes a button, is pressed to flush the toilet. the water used for flushing is stored in the tank ( also called a cistern ) the tank contains some important parts. the next picture shows the parts of a typical tank. the inlet valve controls the water supply coming into the tank. it lets water in when the tank is empty, and stops water coming in when the tank is full. the float ball rises as the tank fills with water. as it rises, the float rod attached to it presses against the inlet valve. when the tank is full, the rod is pressing against the inlet valve hard enough to turn the water off. this stops the tank from overflowing. when you press the handle, a lever inside the tank pulls the piston up, forcing some water through the siphon. this provides suction in the siphon, and the rest of the water follows, emptying


the tank from overflowing. when you press the handle, a lever inside the tank pulls the piston up, forcing some water through the siphon. this provides suction in the siphon, and the rest of the water follows, emptying the tank. the tank empties quite quickly, and the float ball floats to the bottom. that means the float rod is no longer pressing against the valve, so water begins to flow into the tank, filling it up again. the water which left the tank goes through a short pipe to the toilet bowl. it sloshes around the rim, down the sides of the bowl, and out through the drainpipe, cleaning the bowl and carrying the waste with it. some of the clean water coming behind remains at the bottom of the toilet bowl. that ' s because modern toilets have an ' s ' bend which remains filled with water between flushing. the water in the ' s ' bend stops bad odours escaping from the drainpipe. during flushing the ' s ' bend also provides siphon action which helps speed up the flushing process. however, since this type of toilet does not generally handle waste on site, separate waste treatment systems must be built. how dangerous is it? the danger from a toilet isn ' t immediately obvious like that from a hot stove, but people have known for a long time that flushing a toilet can produce very small droplets of water known as aerosols. these aerosols can contain bacteria and viruses that are in the toilet. because the aerosols float through the air and land on surfaces that people might later touch, there is a risk of becoming infected. this has been believed to be a major cause for outbreak of atypical pneumonia within several high - rise residential buildings in hong kong that are close to each other. what does it do? the flush cleans the bowl of the toilet, and under the rim where it is difficult to clean. it carries waste matter to a drain, which then takes it to a treatment plant or septic tank. how does it vary? toilets come in many different types. there are chemical toilets, which use chemicals to neutralize the waste instead of water. there are composting toilets, which are better for the environment because they turn the waste into natural compost. there are even incinerating toilets, which burn the waste. some toilets have extra fixtures such as grab - bars for wheelchair users. some toilets have a water jet built into them like a bidet. some have heated seats, and lids


##post. there are even incinerating toilets, which burn the waste. some toilets have extra fixtures such as grab - bars for wheelchair users. some toilets have a water jet built into them like a bidet. some have heated seats, and lids that open and close automatically. and some will even check your blood pressure and temperature. different toilets use different amounts of water per flush. older models use 13 or even 19 liters per flush while newer models use 6 liters ( 1. 6 gallons ) per flush. today, some well - designed 6 liter toilets flush better than lesser toilets that use 2 - 3 times more water per flush. the design of the surfaces that control the flow of water make a big difference! how has it changed the world? the toilet has made homes, towns and cities cleaner places to live in. because water cleans the toilets very well, highly contagious diseases cannot spread as easily as in the past, where very often thousands of people died at the same time, and to keep epidemics under control, cities and villages weren ' t allowed to grow beyond a certain population. wc helps public health of today to keep higher standards than in the past. that allows us today to live in much bigger cities than in the past, not being afraid of getting sick. big cities were a requirement to start the industrial revolution in the 1800s. we see that although wc seems to be an invention of minor importance, its impact to our modern world was much greater. the toilet has also created a whole new profession like plumber and his associated industry. what idea ( s ) and / or inventions had to be developed before it could be created? to have a flush toilet in your house, first of all one has to have fresh and clean water supply. a better organization of the cities was needed for that. the lever and the siphon also had to be invented before the flush toilet could have come into being.


automatic number plate recognition automatic number plate recognition ( anpr ; see also other names below ) is a mass surveillance method that uses optical character recognition on images to read vehicle registration plates. they can use existing closed - circuit television or road - rule enforcement cameras, or ones specifically designed for the task. they are used by various police forces and as a method of electronic toll collection on pay - per - use roads and cataloging the movements of traffic or individuals. anpr can be used to store the images captured by the cameras as well as the text from the license plate, with some configurable to store a photograph of the driver. systems commonly use infrared lighting to allow the camera to take the picture at any time of the day. anpr technology tends to be region - specific, owing to plate variation from place to place. concerns about these systems have centered on privacy fears of government tracking citizens ' movements, misidentification, high error rates, and increased government spending. other names anpr is sometimes known by various other terms : - automatic license - plate recognition ( alpr ) - automatic vehicle identification ( avi ) - car plate recognition ( cpr ) - license - plate recognition ( lpr ) - lecture automatique de plaques d ' immatriculation ( lapi ) development history anpr was invented in 1976 at the police scientific development branch in the uk. prototype systems were working by 1979, and contracts were let to produce industrial systems, first at emi electronics, and then at computer recognition systems ( crs ) in wokingham, uk. early trial systems were deployed on the a1 road and at the dartford tunnel. the first arrest through detection of a stolen car was made in 1981. the software aspect of the system runs on standard home computer hardware and can be linked to other applications or databases. it first uses a series of image manipulation techniques to detect, normalize and enhance the image of the number plate, and then optical character recognition ( ocr ) to extract the alphanumerics of the license plate. anpr systems are generally deployed in one of two basic approaches : one allows for the entire process to be performed at the lane location in real - time, and the other transmits all the images from many lanes to a remote computer location and performs the ocr process there at some later point in time. when done at the lane site, the information captured of the plate alphanumeric, date - time, lane identification, and any other information required is completed in approximately 250 milliseconds


the ocr process there at some later point in time. when done at the lane site, the information captured of the plate alphanumeric, date - time, lane identification, and any other information required is completed in approximately 250 milliseconds. this information can easily be transmitted to a remote computer for further processing if necessary, or stored at the lane for later retrieval. in the other arrangement, there are typically large numbers of pcs used in a server farm to handle high workloads, such as those found in the london congestion charge project. often in such systems, there is a requirement to forward images to the remote server, and this can require larger bandwidth transmission media. anpr uses optical character recognition ( ocr ) on images taken by cameras. when dutch vehicle registration plates switched to a different style in 2002, one of the changes made was to the font, introducing small gaps in some letters ( such as p and r ) to make them more distinct and therefore more legible to such systems. some license plate arrangements use variations in font sizes and positioning — anpr systems must be able to cope with such differences in order to be truly effective. more complicated systems can cope with international variants, though many programs are individually tailored to each country. the cameras used can include existing road - rule enforcement or closed - circuit television cameras, as well as mobile units, which are usually attached to vehicles. some systems use infrared cameras to take a clearer image of the plates. anpr in mobile systems recent advances in technology have taken automatic number plate recognition ( anpr ) systems from fixed applications to mobile ones. scaled - down components at more cost - effective price points have led to a record number of deployments by law enforcement agencies around the world. smaller cameras with the ability to read license plates at high speeds, along with smaller, more durable processors that fit in the trunks of police vehicles, allow law enforcement officers to patrol daily with the benefit of license plate reading in real time, when they can interdict immediately. despite their effectiveness, there are noteworthy challenges related with mobile anprs. one of the biggest is that the processor and the cameras must work fast enough to accommodate relative speeds of more than 100 mph ( 160 km / h ), a likely scenario in the case of oncoming traffic. this equipment must also be very efficient since the power source is the vehicle battery, and equipment must be small to minimize the space it requires. relative speed is only one issue that affects the camera ' s ability to actually read a license plate. algorithms must


this equipment must also be very efficient since the power source is the vehicle battery, and equipment must be small to minimize the space it requires. relative speed is only one issue that affects the camera ' s ability to actually read a license plate. algorithms must be able to compensate for all the variables that can affect the anpr ' s ability to produce an accurate read, such as time of day, weather and angles between the cameras and the license plates. a system ' s illumination wavelengths can also have a direct impact on the resolution and accuracy of a read in these conditions. installing anpr cameras on law enforcement vehicles requires careful consideration of the juxtaposition of the cameras to the license plates they are to read. using the right number of cameras and positioning them accurately for optimal results can prove challenging, given the various missions and environments at hand. highway patrol requires forward - looking cameras that span multiple lanes and are able to read license plates at very high speeds. city patrol needs shorter range, lower focal length cameras for capturing plates on parked cars. parking lots with perpendicularly parked cars often require a specialized camera with a very short focal length. most technically advanced systems are flexible and can be configured with a number of cameras ranging from one to four which can easily be repositioned as needed. states with rear - only license plates have an additional challenge since a forward - looking camera is ineffective with incoming traffic. in this case one camera may be turned backwards. there are six primary algorithms that the software requires for identifying a license plate : - plate localization – responsible for finding and isolating the plate on the picture. - plate orientation and sizing – compensates for the skew of the plate and adjusts the dimensions to the required size. - normalization – adjusts the brightness and contrast of the image. - character segmentation – finds the individual characters on the plates. - optical character recognition. - syntactical / geometrical analysis – check characters and positions against country - specific rules. the complexity of each of these subsections of the program determines the accuracy of the system. during the third phase ( normalization ), some systems use edge detection techniques to increase the picture difference between the letters and the plate backing. a median filter may also be used to reduce the visual noise on the image. there are a number of possible difficulties that the software must be able to cope with. these include : - poor image resolution, usually because the plate is too far away but sometimes resulting from the use of a low - quality camera. - blur


image. there are a number of possible difficulties that the software must be able to cope with. these include : - poor image resolution, usually because the plate is too far away but sometimes resulting from the use of a low - quality camera. - blurry images, particularly motion blur. - poor lighting and low contrast due to overexposure, reflection or shadows. - an object obscuring ( part of ) the plate, quite often a tow bar, or dirt on the plate. - a different font, popular for vanity plates ( some countries do not allow such plates, eliminating the problem ). - circumvention techniques. - lack of coordination between countries or states. two cars from different countries or states can have the same number but different design of the plate. while some of these problems can be corrected within the software, it is primarily left to the hardware side of the system to work out solutions to these difficulties. increasing the height of the camera may avoid problems with objects ( such as other vehicles ) obscuring the plate but introduces and increases other problems, such as the adjusting for the increased skew of the plate. on some cars, tow bars may obscure one or two characters of the license plate. bikes on bike racks can also obscure the number plate, though in some countries and jurisdictions, such as victoria, australia, " bike plates " are supposed to be fitted. some small - scale systems allow for some errors in the license plate. when used for giving specific vehicles access to a barricaded area, the decision may be made to have an acceptable error rate of one character. this is because the likelihood of an unauthorized car having such a similar license plate is seen as quite small. however, this level of inaccuracy would not be acceptable in most applications of an anpr system. imaging hardware at the front end of any anpr system is the imaging hardware which captures the image of the license plates. the initial image capture forms a critically important part of the anpr system which, in accordance to the garbage in, garbage out principle of computing, will often determine the overall performance. license plate capture is typically performed by specialized cameras designed specifically for the task. factors which pose difficulty for license plate imaging cameras include speed of the vehicles being recorded, varying ambient lighting conditions, headlight glare and harsh environmental conditions. most dedicated license plate capture cameras will incorporate infrared illumination in order to solve the problems of lighting and plate reflectivity. many countries now use license plates that are retroreflective. this returns the


lighting conditions, headlight glare and harsh environmental conditions. most dedicated license plate capture cameras will incorporate infrared illumination in order to solve the problems of lighting and plate reflectivity. many countries now use license plates that are retroreflective. this returns the light back to the source and thus improves the contrast of the image. in some countries, the characters on the plate are not reflective, giving a high level of contrast with the reflective background in any lighting conditions. a camera that makes use of active infrared imaging ( with a normal colour filter over the lens and an infrared illuminator next to it ) benefits greatly from this as the infrared waves are reflected back from the plate. this is only possible on dedicated anpr cameras, however, and so cameras used for other purposes must rely more heavily on the software capabilities. further, when a full - colour image is required as well as use of the anpr - retrieved details it is necessary to have one infrared - enabled camera and one normal ( colour ) camera working together. to avoid blurring it is ideal to have the shutter speed of a dedicated camera set to 1 / 1000 of a second. because the car is moving, slower shutter speeds could result in an image which is too blurred to read using the ocr software, especially if the camera is much higher up than the vehicle. in slow - moving traffic, or when the camera is at a lower level and the vehicle is at an angle approaching the camera, the shutter speed does not need to be so fast. shutter speeds of 1 / 500 of a second can cope with traffic moving up to 40 mph ( 64 km / h ) and 1 / 250 of a second up to 5 mph ( 8 km / h ). license plate capture cameras can now produce usable images from vehicles traveling at 120 mph ( 190 km / h ). to maximize the chances of effective license plate capture, installers should carefully consider the positioning of the camera relative to the target capture area. exceeding threshold angles of incidence between camera lens and license plate will greatly reduce the probability of obtaining usable images due to distortion. manufacturers have developed tools to help eliminate errors from the physical installation of license plate capture cameras circumvention techniques vehicle owners have used a variety of techniques in an attempt to evade anpr systems and road - rule enforcement cameras in general. one method increases the reflective properties of the lettering and makes it more likely that the system will be unable to locate the plate or produce a high enough level of contrast to be able to read it. this is typically done by using


enforcement cameras in general. one method increases the reflective properties of the lettering and makes it more likely that the system will be unable to locate the plate or produce a high enough level of contrast to be able to read it. this is typically done by using a plate cover or a spray, though claims regarding the effectiveness of the latter are disputed. in most jurisdictions, the covers are illegal and covered under existing laws, while in most countries there is no law to disallow the use of the sprays. other users have attempted to smear their license plate with dirt or utilize covers to mask the plate. novelty frames around texas license plates were made illegal in texas on 1 september 2003 by texas senate bill 439 because they caused problems with anpr devices. that law made it a class c misdemeanor ( punishable by a fine of up to us $ 200 ), or class b ( punishable by a fine of up to us $ 2, 000 and 180 days in jail ) if it can be proven that the owner did it to deliberately obscure their plates. the law was later clarified in 2007 to allow novelty frames. if an anpr system cannot read the plate it can flag the image for attention, with the human operators looking to see if they are able to identify the alphanumerics. in order to avoid surveillance or penalty charges, there has been an upsurge in car cloning. this is usually achieved by copying registration plates from another car of a similar model and age. this can be difficult to detect, especially as cloners may change the registration plates and travel behavior to hinder investigations. other possible options include ir emitting leds around the license plate which would serve to " blind " cameras. police enforcement several state police forces, and the department of justice ( victoria ) utilise both fixed and mobile anpr systems. the new south wales police force highway patrol were the first to trial and use a fixed anpr camera system in australia in 2005. in 2009 they began a roll - out of a mobile anpr system ( known officially as manpr ) with three infrared cameras fitted to its highway patrol fleet. the system identifies unregistered and stolen vehicles as well as disqulified or suspended drivers as well as other ' persons of interest ' such as persons having outstanding warrants. on 11 march 2008, the federal constitutional court of germany ruled that some areas of the laws permitting the use of automated number plate recognition systems in germany violated the right to privacy. more specifically, the court found that


such as persons having outstanding warrants. on 11 march 2008, the federal constitutional court of germany ruled that some areas of the laws permitting the use of automated number plate recognition systems in germany violated the right to privacy. more specifically, the court found that the retention of any sort of information ( i. e. number plate data ) which wasn ' t for any pre - destined use ( e. g. for use tracking suspected terrorists or for enforcement of speeding laws ) was in violation of german law. these systems were provided by jenoptik robot gmbh, and called trafficapture. the project of system integration « olli technology » and the ministry of internal affairs of ukraine department of state traffic inspection ( sti ) experiments on the introduction of a modern technical complex which is capable to locate stolen cars, drivers deprived of driving licenses and other problem cars in real time. the ukrainian complex " video control " working by a principle of video fixing of the car with recognition of license plates with check under data base. the city of mechelen uses an anpr system since september 2011 to scan all cars crossing the city limits ( inbound and outbound ). cars listed on ' black lists ' ( no insurance, stolen, etc. ) generate an alarm in the dispatching room, so they can be intercepted by a patrol. as of early 2012, 1 million cars per week are automatically checked in this way. several hungarian auxiliary police units use a system called matrix police in cooperation with the police. it consists of a portable computer equipped with a webcam that scans the stolen car database using automatic number plate recognition. the system is installed on the dashboard of selected patrol vehicles ( pda based handheld versions also exist ) and is mainly used to control the license plate of parking cars. as the auxiliary police doesn ' t have the authority to order moving vehicles to stop, if a stolen car is found, the formal police is informed. several cities have tested and some have put into service the " city security administration system " i. e. capital ankara has debuted kgys - " kent guvenlik yonetim sistemi " which consists of a registration plate number recognition system on the main arteries and city exits. the system has been used with two cameras per lane, one for plate recognition, one for speed detection. now the system has been widened to network all the registration number cameras together, and enforcing average speed over preset distances. some arteries have 70kmh limit, and some 50 kmh, and photo evidence with date - time details are


speed detection. now the system has been widened to network all the registration number cameras together, and enforcing average speed over preset distances. some arteries have 70kmh limit, and some 50 kmh, and photo evidence with date - time details are posted to registration address if speed violation is detected. as of 2012, the fine for exceeding the speed limit for more than 30 % is approximately usd 175. united kingdom the uk has an extensive ( anpr ) automatic number plate recognition cctv network. effectively, the police and security services track all car movements around the country and are able to track any car in close to real time. vehicle movements are stored for 2 years in the national anpr data center to be analyzed for intelligence and to be used as evidence. in 1997 a system of one hundred anpr cameras, codenamed glutton, was installed to feed into the automated british military intelligence systems in northern ireland. further cameras were also installed on the british mainland, including unspecified ports on the east and west coasts. united states in the united states, anpr systems are more commonly referred to as alpr ( automatic license plate reader / recognition ) technology, due to differences in language ( i. e. " number plates " are referred to as " license plates " in american english ) jurisdictions in the u. s. have stated a number of reasons for alpr surveillance cameras, ranging from locating drivers with suspended licenses or no insurance, to finding stolen vehicles and " amber alerts ". with funding from the insurance lobby, oklahoma introduced alpr with the promise of eliminating uninsured motorists, by integrating it with its existing pikepass hybrid rfid / ocr toll collection system, and unmarked police vehicles used for intelligence gathering. oklahoma replaced all license tags with alpr - compatible plates in 2009. in arizona, insurance companies are helping to fund the purchase of alpr systems for their local law enforcement agencies to aid in the recovery of stolen vehicles. other alpr uses include parking enforcement, and revenue collection from individuals who are delinquent on city or state taxes or fines. the technology is often featured in the reality tv show parking wars featured on a & e network. in the show, tow truck drivers and booting teams use the alpr to find delinquent vehicles with high amounts of unpaid parking fines. a recent initiative by new york state deployed alpr systems to catch car thieves by tracing suspect plates back to forged documents. police from albany, new york also scan vehicles in their parking lots to check visitors for warrants.


amounts of unpaid parking fines. a recent initiative by new york state deployed alpr systems to catch car thieves by tracing suspect plates back to forged documents. police from albany, new york also scan vehicles in their parking lots to check visitors for warrants. in addition to the real - time processing of license plate numbers, alpr systems in the us collect ( and can indefinitely store ) data from each license plate capture. images, dates, times and gps coordinates can be stockpiled and can help place a suspect at a scene, aid in witness identification, pattern recognition or the tracking of individuals. such data can be used to create specialized databases that can be shared among departments or individuals ( such as insurers, banks or auto recovery " repo - men ". ) specialized databases can also be used to compile personal information on individuals such as journalists suspected gang members, employees of a business, patrons of a bar, etc., and be shared by e - mail or portable flash media. from time to time, states will make significant changes in their license plate protocol that will affect ocr accuracy. they may add a character or add a new license plate design. alpr systems must adapt to these changes quickly in order to be effective. for the most part, however, the north american design will be based on a variation of the " zurich extra condensed " font. another challenge with alpr systems is that some states have the same license plate protocol. for example more than one state uses the standard three letters followed by four numbers. so each time the alpr systems alarms, it is the user ’ s responsibility to make sure that the plate which caused the alarm matches the state associated with the license plate listed on the in - car computer. average - speed cameras this works by tracking vehicles ' travel time between two fixed points, and calculating the average speed. these cameras are claimed to have an advantage over traditional speed cameras in maintaining steady legal speeds over extended distances, rather than encouraging heavy braking on approach to specific camera locations and subsequent acceleration back to illegal speeds. the netherlands average speed cameras ( trajectcontrole ) are in place in the netherlands since 2002. as of july 2009, 12 such cameras are operating, mostly in the west of the country and along the a12. some of these are divided in several “ sections ” to allow for cars leaving and entering the motorway. a first experimental system was tested on a short stretch of the a2 in 1997 and was deemed a big success by the police, reducing overspeeding to 0.


these are divided in several “ sections ” to allow for cars leaving and entering the motorway. a first experimental system was tested on a short stretch of the a2 in 1997 and was deemed a big success by the police, reducing overspeeding to 0. 66 %, compared to 5 to 6 % when regular speed cameras were used at the same location. the first permanent average speed cameras were installed on the a13 in 2002, shortly after the speed limit was reduced to 80 km / h to limit noise and air pollution in the area. in 2007, average speed cameras resulted in 1. 7 million fines for overspeeding out of a total of 9. 7 millions. according to the dutch attorney general, the average number of violation of the speed limits on motorway sections equipped with average speed cameras is between 1 and 2 %, compared to 10 to 15 % elsewhere. one of the most notable stretches of average speed cameras in the uk is found on the a77 road in scotland, with 32 miles ( 51 km ) being monitored between glasgow and ayr. in 2006 it was confirmed that speeding tickets could potentially be avoided from the ' specs ' cameras by changing lanes and the rac foundation feared that people may play " russian roulette " changing from one lane to another to lessen their odds of being caught. however, in 2007 the system was upgraded for multi - lane use and in 2008 the manufacturer described the " myth " as “ categorically untrue ”. there exists evidence that implementation of systems such as specs has a considerable effect on the volume of drivers travelling at excessive speeds ; on the stretch of road mentioned above ( a77 between glasgow and ayr ) there has been noted a " huge drop " in speeding violations since the introduction of a specs system. traffic control many cities and districts have developed traffic control systems to help monitor the movement and flow of vehicles around the road network. this had typically involved looking at historical data, estimates, observations and statistics such as : - car park usage - pedestrian crossing usage - number of vehicles along a road - areas of low and high congestion - frequency, location and cause of road works cctv cameras can be used to help traffic control centres by giving them live data, allowing for traffic management decisions to be made in real - time. by using anpr on this footage it is possible to monitor the travel of individual vehicles, automatically providing information about the speed and flow of various routes. these details can highlight problem areas as and when they occur and helps the centre to make informed


time. by using anpr on this footage it is possible to monitor the travel of individual vehicles, automatically providing information about the speed and flow of various routes. these details can highlight problem areas as and when they occur and helps the centre to make informed incident management decisions. some counties of the united kingdom have worked with siemens traffic to develop traffic monitoring systems for their own control centres and for the public. projects such as hampshire county council ' s romanse provide an interactive and real - time web site showing details about traffic in the city. the site shows information about car parks, ongoing road works, special events and footage taken from cctv cameras. anpr systems can be used to provide average driving times along particular routes, giving drivers the ability to choose which one to take. romanse also allows travellers to see the current situation using a mobile device with an internet connection ( such as wap, gprs or 3g ), thus allowing them to be alerted to any problems that are ahead. the uk company trafficmaster has used anpr since 1998 to estimate average traffic speeds on non - motorway roads without the results being skewed by local fluctuations caused by traffic lights and similar. the company now operates a network of over 4000 anpr cameras, but claims that only the four most central digits are identified, and no numberplate data is retained. - ieee transactions on intelligent transportation systems ( ieee intelligent transportation systems society ) published some papers on the plate number recognition technologies and applications. [ relevant? ] electronic toll collection toll roads ontario ' s 407 etr highway uses a combination of anpr and radio transponders to toll vehicles entering and exiting the road. radio antennas are located at each junction and detect the transponders, logging the unique identity of each vehicle in much the same way as the anpr system does. without anpr as a second system it would not be possible to monitor all the traffic. drivers who opt to rent a transponder for c $ 2. 55 per month are not charged the " video toll charge " of c $ 3. 60 for using the road, with heavy vehicles ( those with a gross weight of over 5, 000 kg ) being required to use one. using either system, users of the highway are notified of the usage charges by post. - the golden gate bridge in san francisco, california began using an all - electronic tolling system combining fastrak and anpr on march 27, 2013. - nc quick pass for the interstate 540 ( north carolina ) triangle expressway in wake county, north carolina - bridge


gate bridge in san francisco, california began using an all - electronic tolling system combining fastrak and anpr on march 27, 2013. - nc quick pass for the interstate 540 ( north carolina ) triangle expressway in wake county, north carolina - bridge pass for the saint john harbour bridge in saint john, new brunswick - quickpass at the golden ears bridge, crossing the fraser river between langley and maple ridge - citylink & eastlink in melbourne, australia - gateway motorway and logan motorway, brisbane, australia - fastrak in california, united states - highway 6 in israel - tunnels in hong kong - autopista central in santiago, chile ( site in spanish ) - e - zpass in new york, new jersey, massachusetts ( as fast lane until 2012 ), virginia ( formerly smart tag ), and other states. maryland route 200 uses a combination of e - zpass and anpr. - tolltag in north texas. - i - pass in illinois - pike pass in oklahoma. - ogs ( otomatik gecis sistemi ) used at bosphorus bridge, fatih sultan mehmet bridge, and trans european motorway entry points in istanbul, turkey. - m50 westlink toll in dublin, ireland - hi - pass in south korea - northern gateway, sh 1, auckland, new zealand - governor albert d. rosellini bridge, seattle, wa | this section does not cite any references or sources. ( december 2012 ) | portuguese roads have old highways with toll station where drivers can pay with cards and also lanes where there are electronic collection systems. however most new highways only have the option of electronic toll collection system. the electronic toll collection system comprises three different structures : anpr which works with infrared cameras and reads license plates from every vehicle lasers to measure the volumetry of the vehicle to confirm whether it is a regular car or if it is a suv or truck as charges are very different rfid - like to read smart tags that cars can have installed. when the smart tag is installed, the car is quickly identified and owners bank account is automatically deducted. this process is realized at any speed up to over 250 km per hour. if the car does not have the smart tag, the driver is required to go to a pay station to pay the tolls between 3rd and 5th day after with a surplus charge. if he fails to do so, the owner is sent a letter home with a heavy fine. if this is not paid, it increases five - fold and after that, the car is


tolls between 3rd and 5th day after with a surplus charge. if he fails to do so, the owner is sent a letter home with a heavy fine. if this is not paid, it increases five - fold and after that, the car is inserted into a police database for vehicle impounding. this system is also used in some limited access areas of main cities to allow only entry from pre - registered residents. it is planned to be implemented both in more roads and in city entrance toll collection / access restriction. the efficacy of the system is considered to be so high that it is almost impossible for the driver to complain. charge zones – the london congestion charge the london congestion charge is an example of a system that charges motorists entering a payment area. transport for london ( tfl ) uses anpr systems and charges motorists a daily fee of £10 paid before 10pm if they enter, leave or move around within the congestion charge zone between 7 a. m. and 6 : 00 p. m., monday to friday. a reduced fee of £9 is paid by vehicle owners who sign up for the automatic deduction scheme. fines for traveling within the zone without paying the charge are £60 per infraction if paid before the deadline, doubling to £120 per infraction thereafter. there are currently 1, 500 cameras, which use automatic number plate recognition ( anpr ) technology. there are also a number of mobile camera units which may be deployed anywhere in the zone. it is estimated that around 98 % of vehicles moving within the zone are caught on camera. the video streams are transmitted to a data centre located in central london where the anpr software deduces the registration plate of the vehicle. a second data centre provides a backup location for image data. both front and back number plates are being captured, on vehicles going both in and out – this gives up to four chances to capture the number plates of a vehicle entering and exiting the zone. this list is then compared with a list of cars whose owners / operators have paid to enter the zone – those that have not paid are fined. the registered owner of such a vehicle is looked up in a database provided by the dvla. in stockholm, sweden, anpr is used for the stockholm congestion tax, owners of cars driving into or out of the inner city must pay a charge, depending on the time of the day. from 2013, also for the gothenburg congestion tax, which also includes vehicles passing the city on the main highways. the introduction of anpr systems


cars driving into or out of the inner city must pay a charge, depending on the time of the day. from 2013, also for the gothenburg congestion tax, which also includes vehicles passing the city on the main highways. the introduction of anpr systems has led to fears of misidentification and the furthering of 1984 - style surveillance. in the united states, some such as gregg easterbrook oppose what they call " machines that issue speeding tickets and red - light tickets " as the beginning of a slippery slope towards an automated justice system : - " a machine classifies a person as an offender, and you can ' t confront your accuser because there is no accuser... can it be wise to establish a principle that when a machine says you did something illegal, you are presumed guilty? " similar criticisms have been raised in other countries. easterbrook also argues that this technology is employed to maximize revenue for the state, rather than to promote safety. the electronic surveillance system produces tickets which in the us are often in excess of $ 100, and are virtually impossible for a citizen to contest in court without the help of an attorney. the revenues generated by these machines are shared generously with the private corporation that builds and operates them, creating a strong incentive to tweak the system to generate as many tickets as possible. older systems had been notably unreliable ; in the uk this has been known to lead to charges being made incorrectly with the vehicle owner having to pay £10 in order to be issued with proof ( or not ) of the offense. improvements in technology have drastically decreased error rates, but false accusations are still frequent enough to be a problem. perhaps the best known incident involving the abuse of an anpr database in north america is the case of edmonton sun reporter kerry diotte in 2004. diotte wrote an article critical of edmonton police use of traffic cameras for revenue enhancement, and in retaliation was added to an anpr database of " high - risk drivers " in an attempt to monitor his habits and create an opportunity to arrest him. the police chief and several officers were fired as a result, and the office of the privacy commissioner of canada expressed public concern over the " growing police use of technology to spy on motorists. " other concerns include the storage of information that could be used to identify people and store details about their driving habits and daily life, contravening the data protection act along with similar legislation ( see personally identifiable information ). the laws in the uk are strict for any system that uses cctv footage and can identify individuals


identify people and store details about their driving habits and daily life, contravening the data protection act along with similar legislation ( see personally identifiable information ). the laws in the uk are strict for any system that uses cctv footage and can identify individuals. there is also a case in the uk for saying that use of anpr cameras is against the law under the regulation of investigatory powers act 2000. the breach exists, some say, in the fact that anpr is used to monitor the activities of law - abiding citizens and treats everyone like the suspected criminals intended to be surveyed under the act. the police themselves have been known to refer to the system of anpr as a " 24 / 7 traffic movement database " which is a diversion from its intended purpose of identifying vehicles involved in criminal activities. the associated press reported in august 2011 that new york police department cars and license plate tracking equipment purchased with federal hidta ( high intensity drug trafficking area ) funds were used to spy on muslims at mosques, and to track the license plate numbers of worshipers. police in unmarked cars outfitted with electronic license plate readers would drive down the street and automatically catalog the plates of everyone parked near the mosque, amassing a covert database that would be distributed among officers and used to profile muslims in public. other uses anpr systems may also be used for / by : - section control, to measure average vehicle speed over longer distances. - border crossings - automobile repossessions - petrol stations to log when a motorist drives away without paying for their fuel. - a marketing tool to log patterns of use - targeted advertising, a - la " minority report " - style billboards. - traffic management systems, which determine traffic flow using the time it takes vehicles to pass two anpr sites - analyses of travel behaviour ( route choice, origin - destination etc. ) for transport planning purposes - drive through customer recognition, to automatically recognize customers based on their license plate and offer them the items they ordered the last time they used the service, improving service to the customer. - to assist visitor management systems in recognizing guest vehicles. - police and auxiliary police - car parking companies. related research society measuring anpr system performance a 2008 article in parking trend international discussed a disparity in claimed vs. experienced license plate recognition read rates, with manufacturers claiming that their recognition engines can correctly report 98 % of the time, although customers experience only 90 % to 94 % success, even with new equipment under perfect conditions. early systems were reportedly only 60 % to 80 % reliable.


read rates, with manufacturers claiming that their recognition engines can correctly report 98 % of the time, although customers experience only 90 % to 94 % success, even with new equipment under perfect conditions. early systems were reportedly only 60 % to 80 % reliable. true system error rate is the product of its subsystem error rates ( image capture, license plate image extraction, lp image interpretation ) ; slight increases in subsystem error rates can produce dramatic reductions of read rates. the effects of real - world interfering factors on read rate are not uniformly specified or tested by manufacturers. the article states " there is a need for the industry to adopt a standard performance measurement protocol to enable potential customers assess the best fit for their particular requirements. " see also | wikimedia commons has media related to : automatic number plate recognition | - ai effect - applications of artificial intelligence - facial recognition system - road policing unit - specs ( speed camera ) - closed circuit television - ieee intelligent transportation systems society - " anpr tutorial ". anpr tutorial. 15 august 2006. retrieved 2012 - 01 - 24. - " an introduction to anpr ". cctv - information. co. uk. retrieved 2012 - 01 - 24. - " plate recognition ". photocop. com. - " algorithm for license plate recognition ". visl, technion. 2002. - " a real - time vehicle license plate recognition ( lpr ) ". visl, technion, 2003 - " an approach to license plate recognition " ( pdf ). university of calgary. 1996. retrieved 2012 - 01 - 24. - draghici, sorin ( 1997 ). " a neural network based artificial vision system for license plate recognition " ( pdf ). dept. of computer science, wayne state university. retrieved 2012 - 01 - 24. - " license plate recognition in turkey ( plaka okuma sistemi ) ". grimedia. com. retrieved 2012 - 01 - 24. - kwasnicka, halina ; wawrzyniak, bartosz ( 2002 ). " license plate localization and recognition in camera pictures " ( pdf ). retrieved 2012 - 01 - 24. - kahraman, fatih ; gokmen, muhittin ( 2003 ). " license plate character segmentation based on the gabor transform and vector quantization " ( pdf ). archived from the original on 2006 - 05 - 24. retrieved 2012 - 01 - 24. - ondrej martins


. edmonton sun. 21 september 2005. retrieved 2012 - 01 - 24. - " embossed license plate fonts vs. 3m ’ s default font for flat digital plates ". leewardpro. com. retrieved 2012 - 01 - 24. - " section control : 24. 000 raser angezeigt " ( in german ). austria : orf. at. 7 june 2010. - " ecco come funziona il tutor in autostrada - notizie brevi - news - informazione - a. s. a. p. s. il portale della sicurezza stradale ". asaps. it. retrieved 2012 - 08 - 03. - " description of the system " ( in dutch ). dutch attorney general. 31 december 2009. retrieved 2012 - 01 - 24. - " llegan los radares de velocidad media a espana " ( in spanish ). noticias. coches. com. 23 september 2009. retrieved 2012 - 01 - 24. - " speeding tickets can potentially be avoided by changing lanes ". the daily mail ( london ). 15 october 2006. retrieved 2012 - 01 - 24. " the home office admitted last night that drivers can avoid being caught the by hi - tech ' specs ' cameras which calculate a car ' s average speed over a long distance. " - " frequently asked question over trajectcontrole " ( in dutch ). dutch attorney general. retrieved 2012 - 01 - 24. - " niemand rijdt meer te hard op de a2 " ( in dutch ). trouw. 18 october 1997. retrieved 2012 - 01 - 24. - " nummerborden lezen op de a13 " ( in dutch ). trouw. 6 may 2002. retrieved 2012 - 01 - 24. - kreling, tom ( 28 august 2008 ). " een duur foutje van de computer " ( in dutch ). nrc handelsblad. retrieved 2012 - 01 - 24. - " specs - average speed cameras on specs ". a77safetygroup. com. 14 july 2005. retrieved 2012 - 01 - 24. - " jeremy clarkson tilts at windmills – speed camera avoidance is an urban myth ". the register. 21 july 2008. retrieved 23 january 2012. - " autostrade s. p. a " ( in ( italian ) ). autostrade. it. 2008 - 05


. net ". london : the register. retrieved 2012 - 01 - 24. - " anpr strategy for the police service 2005 / 2006 ". acpo ( association of chief police officers ) anpr steering group. 17 march 2005. archived from the original on 2010 - 03 - 31. retrieved 2012 - 01 - 24. - " driving crime down " ( pdf ). london : uk government home office. october 2004. retrieved 29 march 2005. - constant, mike. " anpr ". cctv information. archived from the original on 21 march 2005. retrieved 30 march 2005. - hofman, yoram. " license plate recognition – a tutorial ". archived from the original on 24 march 2005. retrieved 28 march 2005. - lucena, raul ( 24 august 2006 ). " automatic number plate recognition tutorial ". anpr - tutorial. com. - lettice, john ( 24 march 2005 ). " no hiding place? uk number plate cameras go national ". the register. archived from the original on 28 march 2005. retrieved 28 march 2005. - " recognizing a new way to keep traffic moving ". siemens traffic. archived from the original on 17 april 2005. retrieved 3 april 2005. - clements, jon ( 11 march 2008 ). " uk : traffic camera data dropped in gutter ". mirror. co. uk. retrieved 2012 - 01 - 24. - " clements ". the mirror ( uk ). 11 march 2008. retrieved 2012 - 01 - 24. unknown parameter - " regulation of investigatory powers act 2000 ". legislation. gov. uk. the national archives. 2000. retrieved 2012 - 01 - 24. - " police number plate cameras may breach ripa - commissioner ". theregister. com. 17 july 2006. retrieved 2012 - 01 - 24. - " money for nothing : the drug war and the war on muslims ". - " nypd defends tactics over mosque spying ; records reveal new details on muslim surveillance ". - " section control ". verkeershandhaving dossiers. archived from the original on 2006 - 05 - 12. retrieved 2012 - 01 - 24. - " high - tech system helps repo man find cars ". wftv. november 11, 2009. - " uk billboards equipped with license plate spy cameras ". thenewspaper. com. 25 september 2009. retrieved 2012 - 01 - 24. unknown parameter - " extreme cctv announces contract for stockholm traffic cameras " ( pdf )


| | this article includes a list of references, related reading or external links, but its sources remain unclear because it lacks inline citations. ( december 2011 ) | a counterfactual conditional, subjunctive conditional, or remote conditional, abbreviated cf, is a conditional ( or " if - then " ) statement indicating what would be the case if its antecedent were true ( although it is not true ). this is to be contrasted with an indicative conditional, which indicates what is ( in fact ) the case if its antecedent is ( in fact ) true ( which it may or may not be ). the difference between indicative and counterfactual conditionals, in a context of past time reference, can be illustrated with a pair of examples in which the if clause is in the past indicative in the first example but in the pluperfect subjunctive in the second : - if oswald did not shoot kennedy, then someone else did. - if oswald had not shot kennedy, then someone else would have. the protasis ( the if clause ) of the first sentence may or may not be true according to the speaker, so the apodosis ( the then clause ) also may or may not be true ; the apodosis is said by the speaker to be true if the protasis is true. in this sentence the if clause and the then clause are both in the past tense of the indicative mood. in the second sentence, the speaker is speaking with a certainty that oswald did shoot kennedy ( according to the speaker, the protasis is false ), and therefore the main clause deals with the counterfactual result — what would have happened. in this sentence the if clause is in the pluperfect subjunctive form of the subjunctive mood, and the then clause is in the conditional perfect form of the conditional mood. a corresponding pair of examples with present time reference uses the present indicative in the if clause of the first sentence but the past subjunctive in the second sentence ' s if clause : - if it is raining, then he is inside. - if it were raining, then he would be inside. here again, in the first sentence the if clause may or may not be true ; the then clause may or may not be true but certainly ( according to the speaker ) is true conditional on the if clause being true. here both the if clause and the then clause are in the present indicative. in the second sentence, the if clause is not true, while the


not be true but certainly ( according to the speaker ) is true conditional on the if clause being true. here both the if clause and the then clause are in the present indicative. in the second sentence, the if clause is not true, while the then clause may or may not be true but certainly would be true in the counterfactual circumstance of the if clause being true. in this sentence the if clause is in the past subjunctive form of the subjunctive mood, and the then clause is in the conditional mood. people engage in counterfactual thinking frequently. experimental evidence indicates that people ' s thoughts about counterfactual conditionals differ in important ways from their thoughts about indicative conditionals. participants in experiments were asked to read sentences, including counterfactual conditionals, e. g., ' if mark had left home early he would have caught the train '. afterwards they were asked to identify which sentences they had been shown. they often mistakenly believed they had been shown sentences corresponding to the presupposed facts, e. g., ' mark did not leave home early ' and ' mark did not catch the train ' ( fillenbaum, 1974 ). in other experiments, participants were asked to read short stories that contained counterfactual conditionals, e. g., ' if there had been roses in the flower shop then there would have been lilies '. later in the story they read sentences corresponding to the presupposed facts, e. g., ' there were no roses and there were no lilies '. the counterfactual conditional ' primed ' them to read the sentence corresponding to the presupposed facts very rapidly ; no such priming effect occurred for indicative conditionals ( santamaria, espino, and byrne, 2005 ). they spend different amounts of time ' updating ' a story that contains a counterfactual conditional compared to one that contains factual information ( de vega, urrutia, and riffo, 2007 ) and they focus on different parts of counterfactual conditionals ( ferguson and sanford, 2008 ). experiments have compared the inferences people make from counterfactual conditionals and indicative conditionals. given a counterfactual conditional, e. g., ' if there had been a circle on the blackboard then there would have been a triangle ', and the subsequent information ' in fact there was no triangle ', participants make the modus tollens inference ' there was no


e. g., ' if there had been a circle on the blackboard then there would have been a triangle ', and the subsequent information ' in fact there was no triangle ', participants make the modus tollens inference ' there was no circle ' more often than they do from an indicative conditional ( byrne and tasso, 1999 ). given the counterfactual conditional and the subsequent information ' in fact there was a circle ', participants make the modus ponens inference as often as they do from an indicative conditional. psychological accounts ruth m. j. byrne proposed in the rational imagination : how people create alternatives to reality that people construct mental representations that encompass two possibilities when they understand, and reason from, a counterfactual conditional, e. g., ' if oswald had not shot kennedy, then someone else would have '. they envisage the conjecture ' oswald did not shoot kennedy and someone else did ' and they also think about the presupposed facts ' oswald did shoot kennedy and someone else did not ' ( byrne, 2005 ). according to the mental model theory of reasoning, they construct mental models of the alternative possibilities, as described in deduction ( johnson - laird and byrne, 1991 ). philosophical treatments in order to distinguish counterfactual conditionals from material conditionals, a new logical connective ' > ' is defined, where a > b can be interpreted as " if it were the case that a, then it would be the case that b. " the truth value of a material conditional, a → b, is determined by the truth values of a and b. this is not so for the counterfactual conditional a > b, for there are different situations agreeing on the truth values of a and b but which yield different evaluations of a > b. for example, if keith is in germany, the following two conditionals have both a false antecedent and a false consequent : - if keith were in mexico then he would be in africa. - if keith were in mexico then he would be in north america. indeed, if keith is in germany, then all three conditions " keith is in mexico ", " keith is in africa ", and " keith is in north america " are false. however, ( 1 ) is obviously false, while ( 2 ) is true as mexico is part of north america. possible world semantics philosophers such as david lewis and robert stalnaker modeled counterfactuals using the possible world semantics of modal


, ( 1 ) is obviously false, while ( 2 ) is true as mexico is part of north america. possible world semantics philosophers such as david lewis and robert stalnaker modeled counterfactuals using the possible world semantics of modal logic. the semantics of a conditional a > b are given by some function on the relative closeness of worlds where a is true and b is true, on the one hand, and worlds where a is true but b is not, on the other. on lewis ' s account, a > c is ( a ) vacuously true if and only if there are no worlds where a is true ( for example, if a is logically or metaphysically impossible ) ; ( b ) non - vacuously true if and only if, among the worlds where a is true, some worlds where c is true are closer to the actual world than any world where c is not true ; or ( c ) false otherwise. although in lewis ' s counterfactuals it was unclear what he meant by ' closeness ', in later writings, lewis made it clear that he did not intend the metric of ' closeness ' to be simply our ordinary notion of overall similarity. consider an example : - if i had eaten more at breakfast, i would not have been hungry at 11am. on lewis ' s account, the truth of this statement consists in the fact that, among possible worlds where i ate more for breakfast, there is at least one world where i am not hungry at 11am and which is closer to our world than any world where i ate more for breakfast but am still hungry at 11am. stalnaker ' s account differs from lewis ' s most notably in his acceptance of the limit and uniqueness assumptions. the uniqueness assumption is the thesis that, for any antecedent a, there is a unique possible world where a is true, while the limit assumption is the thesis that, for a given antecedent a, there is a unique set of worlds where a is true that are closest. ( notice that the uniqueness assumption entails the limit assumption, but the limit assumption does not entail the uniqueness assumption. ) on stalnaker ' s account, a > c is non - vacuously true if and only if, at the closest world where a is true, c is true. so, the above example is true just in case at the single, closest world where i eat more breakfast, i don ' t feel hungry at 11am.


if and only if, at the closest world where a is true, c is true. so, the above example is true just in case at the single, closest world where i eat more breakfast, i don ' t feel hungry at 11am. although it is controversial, lewis rejected the limit assumption ( and therefore the uniqueness assumption ) because it rules out the possibility that there might be worlds that get closer and closer to the actual world without limit. for example, there might be an infinite series of worlds, each with my coffee cup a smaller fraction of an inch to the left of its actual position, but none of which is uniquely the closest. ( see lewis 1973 : 20. ) one consequence of stalnaker ' s acceptance of the uniqueness assumption is that, if the law of excluded middle is true, then all instances of the formula ( a > c ) ∨ ( a > ¬c ) are true. the law of excluded middle is the thesis that for all propositions p, p ∨ ¬p is true. if the uniqueness assumption is true, then for every antecedent a, there is a uniquely closest world where a is true. if the law of excluded middle is true, any consequent c is either true or false at that world where a is true. so for every counterfactual a > c, either a > c or a > ¬c is true. this is called conditional excluded middle ( cem ). consider the following example : - ( 1 ) if the coin had been flipped, it would have landed heads. - ( 2 ) if the coin had been flipped, it would have landed tails ( i. e. not heads ). on stalnaker ' s analysis, there is a closest world where the coin mentioned in ( 1 ) and ( 2 ) is flipped and at that world either it lands heads or it lands tails. so either ( 1 ) is true and ( 2 ) is false or ( 1 ) is false and ( 2 ) true. on lewis ' s analysis, however, both ( 1 ) and ( 2 ) are false, for the worlds where the coin lands heads are no more or less close than the worlds where they land tails. for lewis, ' if the coin had been flipped, it would have landed heads or tails ' is true, but this does not entail that ' if the coin had been flipped, it would have landed heads, or : if the coin had been flipped it would have landed tails. ' other accounts counter


it would have landed heads or tails ' is true, but this does not entail that ' if the coin had been flipped, it would have landed heads, or : if the coin had been flipped it would have landed tails. ' other accounts counterfactual conditionals may also be evaluated using the so - called ramsey test : a > b holds if and only if the addition of a to the current body of knowledge has b as a consequence. this condition relates counterfactual conditionals to belief revision, as the evaluation of a > b can be done by first revising the current knowledge with a and then checking whether b is true in what results. revising is easy when a is consistent with the current beliefs, but can be hard otherwise. every semantics for belief revision can be used for evaluating conditional statements. conversely, every method for evaluating conditionals can be seen as a way for performing revision. ginsberg ( 1986 ) has proposed a semantics for conditionals which assumes that the current beliefs form a set of propositional formulae, considering the maximal sets of these formulae that are consistent with a, and adding a to each. the rationale is that each of these maximal sets represents a possible state of belief in which a is true that is as similar as possible to the original one. the conditional statement a > b therefore holds if and only if b is true in all such sets. within empirical testing the counterfactual conditional is the basis of experimental methods for establishing causality in the natural and social sciences, e. g., whether taking antibiotics helps cure bacterial infection. for every individual, u, there is a function that specifies the state of u ' s infection under two hypothetical conditions : had u taken antibiotic and had u not taken antibiotic. only one of these states can be observed in any instance, since they are mutually exclusive. the overall effect of antibiotic on infection is defined as the difference between these two states, averaged over the entire population. if the treatment and control groups are selected at random, the effect of antibiotic can be estimated by comparing the rates of recovery in the two groups. the tight connection between causal and counterfactual relations has prompted judea pearl ( 2000 ) to reject both the possible world semantics and those of ramsey and ginsberg. the latter was rejected because causal information cannot be encoded as a set of beliefs, and the former because it is difficult to fine - tune lewis ' s similarity measure to match causal intuition. pearl defines counterfactuals directly in terms


ginsberg. the latter was rejected because causal information cannot be encoded as a set of beliefs, and the former because it is difficult to fine - tune lewis ' s similarity measure to match causal intuition. pearl defines counterfactuals directly in terms of a " structural equation model " - - a set of equations, in which each variable is assigned a value that is an explicit function of other variables in the system. given such a model, the sentence " y would be y had x been x " ( formally, x = x > y = y ) is defined as the assertion : if we replace the equation currently determining x with a constant x = x, and solve the set of equations for variable y, the solution obtained will be y = y. this definition has been shown to be compatible with the axioms of possible world semantics and forms the basis for causal inference in the natural and social sciences, since each structural equation in those domains corresponds to a familiar causal mechanism that can be meaningfully reasoned about by investigators. see also - english conditional sentences - indicative conditional - irrealis moods - logical consequence - material conditional - optative mood - principle of explosion - subjunctive mood - thought experiment - possible world semantics - bennett, jonathan. ( 2003 ). a philosophical guide to conditionals. oxford university press. - bonevac, d. ( 2003 ). deduction, introductory symbolic logic. 2nd ed. blackwell publishers. - byrne, r. m. j. ( 2005 ). the rational imagination : how people create alternatives to reality. cambridge, m. a. : mit press. - byrne, r. m. j. & tasso, a. ( 1999 ). deductive reasoning with factual, possible, and counterfactual conditionals. memory & cognition. 27, 726 - 740. - de vega, m., urrutia, m., riffo, b. ( 2007 ). canceling updating in the comprehension of counterfactuals embedded in narrative. memory & cognition, 35, 1410 - 1421. - edgington, dorothy. ( 2001 ). " conditionals ". in goble, lou, ed., the blackwell guide to philosophical logic. blackwell. - edgington, dorothy. ( 2006 ). " conditionals ". the stanford encyclopedia of philosophy, edward zalta ( ed. ). - ferguson, h. j. and sanford, a. j. ( 2008 ) anomalies in real and counterfactual worlds


2006 ). " conditionals ". the stanford encyclopedia of philosophy, edward zalta ( ed. ). - ferguson, h. j. and sanford, a. j. ( 2008 ) anomalies in real and counterfactual worlds : an eye - movement investigation. j. mem. lang. 58, 609 - 626. - fillenbaum, s. ( 1974 ). information amplified : memory for counterfactual conditionals. journal of experimental psychology, 102, 44 - 49. - johnson - laird, p. n. and byrne, r. m. j. ( 1991 ). deduction. hillsdale, nj : erlbaum. - morgan, stephen l. and christopher winship. ( 2007 ). " counterfactuals and causal inference : methods and principles of social research ". cambridge eprint. - ginsberg, m. l. ( 1986 ). " counterfactuals ". artificial intelligence, 30 : 35 - 79. - lewis, david. ( 1973 ). counterfactuals. blackwell publishers. isbn 0 - 631 - 22425 - 4 - santamaria, c., espino, o. and byrne, r. m. j. ( 2005 ). counterfactual and semifactual conditionals prime alternative possibilities. journal of experimental psychology : learning, memory and cognition. 31, 1149 – 1154 - thompson, v. and byrne, r. m. j. ( 2002 ). reasoning about things that didn ' t happen. journal of experimental psychology : learning, memory, and cognition. 28, 1154 - 1170.


history and location the church at dode was built during the reign of william ii of england at some point between 1087 and 1100. it was built on a man - made mound. the nearby hill is known as " holly hill " which is a corruption of " holy hill ", and the lane which leads to the village is " wrangling lane ", showing that the mound could be the site of a meeting place. the church stands at the end of a 10 - mile long easterly running ley line connecting three pre - reformation churches, two roman sites, a bronze age burial ground, and two of the medway megaliths - the coffin stone and kit ' s coty house. the village of dode was virtually wiped out by the black death during the 14th century, and its church last used as a place of worship in 1367, then deconsecrated on the orders of thomas trilleck, the bishop of rochester. it was originally twinned with another early norman church in paddlesworth ( now in snodland ). according to local legend, the last survivor of the black death at dode was a seven - year - old girl known as the dodechild. it is said she took refuge in the church after all the other villagers were dead, and died within its walls. the dodechild is supposed to haunt the churchyard, having first appeared on a sunday morning each month for several years, and then every seven years. rebuilding of the church following the black death, the village was abandoned, and the church stood empty for centuries. in 1901 it was purchased by an antiquarian, george m arnold, mayor of gravesend. he restored the walls and roof of the church and in 1954 the arnold family returned the building to the catholic church. it was rededicated as the church of our lady of the meadows and mass was celebrated there at least once a year. eventually the building deteriorated again and was vandalised. in 1990 doug chapman, a chartered surveyor who had worked at canterbury cathedral, purchased the church and began restoring the building, originally with the intention of turning it into a weekend home. since 1999 it has been licensed as a civil wedding venue. the wedding venue hit the british press in december 2009 because of the snowfall which occurred across the country. a bride - to - be called bbc radio kent for assistance when she realised that the transport arranged for her wedding would not be able to travel down the narrow lane to dode. a number of volunteers stepped forward, providing enough


occurred across the country. a bride - to - be called bbc radio kent for assistance when she realised that the transport arranged for her wedding would not be able to travel down the narrow lane to dode. a number of volunteers stepped forward, providing enough four - wheel drive cars to transport the wedding party and their guests both to the venue at dode, and then afterwards to the leather bottle pub in cobham. see also - glancey, jonathan ( 1996 - 04 - 16 ). " one man ' s revival of ancient english rites ". independent. co. uk. retrieved 2009 - 12 - 19. - chapman, doug. " a brief history of dode ". dodevillage. com. retrieved 2009 - 12 - 19. - " the lost village of dowde ". haunted kent. retrieved 2009 - 12 - 18. [ dead link ] - " a brief explanatory note on the churches and parishes of paddlesworth and dode ". medway. gov. uk. retrieved 2009 - 12 - 19. - " tq6663 : dowde ( or dode ) church ". geograph. co. uk. 2006 - 06 - 26. retrieved 2009 - 12 - 18. - " george matthews arnold ". discover gravesham. gravesham borough council. retrieved 2010 - 01 - 14. - " a history of english martyrs strood ". church handbook 1975 – 6. english martyrs roman catholic church. 1975. retrieved 2010 - 01 - 14. - pattison, jo ( 2009 - 12 - 14 ). " discover the lost village of dode ". bbc news. retrieved 2009 - 12 - 18. - " snow almost stops bride getting to the church on time... until some kindly villagers step in ". daily mail. 2009 - 12 - 18. retrieved 2009 - 12 - 19.