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and updating, the use of images remains static in the sense |
that images are mostly used for visualization or, at best, to |
compute standard indices such as the normalized differ - |
ence vegetation index, which is then assumed to represent |
vegetation status. Moreover, models answering the specific |
needs of users are scarce and more often limited to classical |
processing tasks (e.g., car detection or land cover mapping) |
and cannot cover the variety of tasks in which different us - |
ers could be interested. Another limitation is that end users |
rarely have the technical skills necessary to design and run |
ML models and would like to receive an answer to a spe - |
cific question of interest asked in a natural language (e.g., |
in English). |
Fortunately, many of these questions boil down to the |
presence of objects, to counting, or to some kind of re - |
lational attribute (e.g., whether there was an increase of |
forest area or whether there are buildings in risk zones): |
a model capable of pursuing some kind of reasoning |
about the image content (see direction 1 in Table 1 ) but |
taking into account a specific question (in English) by |
a user could open the door to a new type of interaction |
with remote sensing. Similar to what search engines do |
on the Internet, a remote sensing VQA (RSVQA) [ 12] en- |
gine could allow anyone, from scientists to laymen and |
journalists, to retrieve relevant information contained in |
the images. |
Research into VQA is a vivid topic in computer vision |
[11], where it has had considerable impact on creating sys - |
tems that support vision-impaired people with everyday |
tasks [ 58]. A traditional VQA system, in this context, can in - |
deed be used to help people when buying groceries, cross - |
ing the street, and so on. |
DIALOGS AMONG USERS AND EARTH OBSERVATION |
IMAGES REQUIRE BOTH REMOTE SENSING AND |
NATURAL LANGUAGE PROCESSING |
In remote sensing, the first VQA system was proposed by |
Lobry et al. [ 12] and is summarized in Figure 3 . To become |
truly general purpose, such a model needs to be trained us - |
ing a large quantity of data from several areas and different |
thematic objectives: in [ 12], two models were designed, one |
for Sentinel-2 data and another for subdecimeter-resolution |
aerial images. The models were trained with large sets of |
image/answer pairs spanning tasks of classification, relative |
position reasoning, and object counting. As a large quantity |
of labels was necessary, OpenStreetMap (OSM) vector data |
were used to automatically generate labels: following the |
Compositional Language and Elementary Visual Reason - |
ing (CLEVR) protocol [ 59], 100 questions per image involv - |
ing objects occurring in the image (as informed by OSM) |
were generated. For each image/question pair, the answer |
(i.e., the label) was automatically obtained by querying |
OSM directly. The data and models are openly available |
Authorized licensed use limited to: ASU Library. Downloaded on March 07,2024 at 22:07:36 UTC from IEEE Xplore. Restrictions apply. |
94 |
IEEE GEOSCIENCE AND REMOTE SENSING MAGAZINE JUNE 2021at https://rsvqa.sylvainlobry.com/. Examples of RSVQA |
model predictions are reported in Figure 4 for both resolu - |
tion images. Note that, for a single image, several questions |
are possible and the same model is used to answer them.PERSPECTIVES |
This first work opens a wide range of possibilities for |
a new line of research toward the next level of human/ |
image interactions. Nonetheless, all the blocks of the |
FIGURE 3. An example of an RSVQA system [12]. (a) A remote sensing image and (b) a question in natural language enter two source-specific |
neural networks, each one outputting a vector representing their information, and (c) both vectors are combined and become (d) the input of |
a classifier that outputs all the possible answers as separate classes. RNN: recurrent neural network. |
“How many cars are |
there?”CNN |
RNN6 |
7 |
8Yes |
No |
Peri Urban |
Cropland |
City Center |
Increasing4) Question Answering 3) Feature |
Fusion 1) Image Representation |
2) Textual Representation(a) |
(b) (c) (d) |
Q: “Is there a road?” |
A: “Yes (GT: yes)” |
Q: “Is there a farm? ” |
A: “Yes (GT: yes)” |
Q: “How many small residential |
buildings are there?” |
A: “Between 10 and 100 (GT: 147)” |
Q: “Is there a residential building?” |
A: “Yes (GT: yes)” |
A: “Yes (GT: yes)” |
Q: “How many small residential |
buildings are there?”Q: “Are there fewer commercial |
buildings than water areas?” |
A: “Between 10 and 100 (GT: 18)”Q: “Is there a baseball field?” |
A: “Yes (GT: yes)” |
A: “0 (GT: 0)” |
Q: “Is there a building south of a road?”Q: “How many commercial buildings are |
close to a baseball field?” |
A: “No (GT: Yes)” |
Q: “Is there a commercial building?” |
A: “No (GT: no)” |
A: “Yes (GT: yes)” |
Q: “How many small buildings are there?”Q: “Are there fewer commercial buildings |
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