eda_report.md

# CPCB Data Pipeline -- EDA Report
Generated: 2026-07-15T10:29:41

## Overview
- Total CSV files scanned: **4468**
- Duplicate-download files skipped (Chrome ' (1).csv' re-downloads): **8**
- Files failed to load: **0**
- Total merged rows: **1,549,637**
- Total rows after column cleanup: **1,549,637**
- Unique cities: **307**
- Unique (city, state) pairs geocoded: **308**
- Unique states (raw folder prefix): **31**
- Unique stations: **566**

## Year Coverage
- 2009 to 2025

| Year | Rows |
|---|---|
| 2009 | 4,761 |
| 2010 | 5,902 |
| 2011 | 8,400 |
| 2012 | 8,906 |
| 2013 | 9,125 |
| 2014 | 8,581 |
| 2015 | 10,283 |
| 2016 | 17,449 |
| 2017 | 165,300 |
| 2018 | 137,436 |
| 2019 | 139,674 |
| 2020 | 142,618 |
| 2021 | 147,705 |
| 2022 | 148,619 |
| 2023 | 191,874 |
| 2024 | 196,971 |
| 2025 | 206,033 |

## Geocoding Confidence (DO NOT assume perfect coords)
| Confidence | # Cities | Meaning |
|---|---|---|
| high | 293 | single unambiguous match, state confirmed |
| not_found | 7 | Nominatim returned nothing |
| medium_state_mismatch | 5 | top match's state disagrees with folder hint |
| low_ambiguous | 3 | multiple candidates found across different states |

Full city-level detail (lat/lon/candidates/queries tried) in `cities_needs_review.csv` for anything not `high`. **Manually verify those before trusting them in AtmosIQ's node graph.**

## Data Quality: State-Prefix Mismatches
Folder-name state prefix vs geocoded actual state disagreed for **69** unique station/city combos. Full list in `state_mismatch_audit.csv`. Sample:

| Folder State (raw) | Geocoded State | City | Station |
|---|---|---|---|
| assam | Meghalaya | Byrnihat | Central Academy for SFS |
| assam | Meghalaya | Byrnihat | Central Academy for SFS |
| assam | Meghalaya | Byrnihat | Central Academy for SFS |
| assam | Meghalaya | Byrnihat | Central Academy for SFS |
| assam | Meghalaya | Byrnihat | Central Academy for SFS |
| assam | Meghalaya | Byrnihat | Central Academy for SFS |
| assam | Meghalaya | Byrnihat | Central Academy for SFS |
| assam | Meghalaya | Byrnihat | Central Academy for SFS |
| assam | Meghalaya | Byrnihat | Central Academy for SFS |
| bihar | Chhattisgarh | Bhilai | 32Bungalows |
| bihar | Chhattisgarh | Bhilai | 32Bungalows |
| bihar | Chhattisgarh | Bhilai | 32Bungalows |
| bihar | Chhattisgarh | Bhilai | 32Bungalows |
| bihar | Chhattisgarh | Bhilai | 32Bungalows |
| bihar | Chhattisgarh | Bhilai | 32Bungalows |

## Columns Dropped
- VOC/organic columns (sparse by CPCB design): Benzene (µg/m³), Toluene (µg/m³), Xylene (µg/m³), O Xylene (µg/m³), Eth-Benzene (µg/m³), MP-Xylene (µg/m³)
- Auto-dropped (>95% NaN dataset-wide): none

## Missing Value % by Column (before cleanup)
| Column | % Missing |
|---|---|
| VWS (m/s) | 88.1% |
| BP (mmHg) | 69.3% |
| RF (mm) | 61.9% |
| AT (°C) | 58.5% |
| SR (W/mt2) | 50.7% |
| NH3 (µg/m³) | 49.1% |
| RH (%) | 45.7% |
| WS (m/s) | 45.3% |
| WD (deg) | 44.7% |
| PM10 (µg/m³) | 43.4% |
| Ozone (µg/m³) | 41.4% |
| PM2.5 (µg/m³) | 40.5% |
| SO2 (µg/m³) | 40.4% |
| CO (mg/m³) | 39.6% |
| NO (µg/m³) | 39.4% |
| NOx (ppb) | 38.7% |
| NO2 (µg/m³) | 38.4% |
| TOT-RF (mm) | 14.0% |
| State_Geocoded | 11.5% |
| state_mismatch_flag | 11.5% |
| lat | 1.7% |
| lon | 1.7% |
| coverage_area_km2 | 1.7% |
| City | 0.2% |
| geocode_confidence | 0.2% |
| FileYear | 0.2% |
| Agency | 0.2% |
| Timestamp | 0.0% |
| Station | 0.0% |
| State_Hint | 0.0% |
| State_Raw | 0.0% |
| SourceFile | 0.0% |

## Cities Not Geocoded
7 (city, state) pairs failed geocoding (need manual lat/lon): Bileipada, DU  Delhi, Kunjemura, Milupara, Palkalaiperur, Suakati, Tumidih

## Filenames That Didn't Match Expected Pattern
9 files -- review naming manually:

- `C:\Users\offrk\Desktop\cpcb\India CPCB\Odisha_Talcher_Coalfields_Talcher_-_OSPCB\Talcher_Coalfields_Talcher_-_OSPCB_2017.csv`
- `C:\Users\offrk\Desktop\cpcb\India CPCB\Odisha_Talcher_Coalfields_Talcher_-_OSPCB\Talcher_Coalfields_Talcher_-_OSPCB_2018.csv`
- `C:\Users\offrk\Desktop\cpcb\India CPCB\Odisha_Talcher_Coalfields_Talcher_-_OSPCB\Talcher_Coalfields_Talcher_-_OSPCB_2019.csv`
- `C:\Users\offrk\Desktop\cpcb\India CPCB\Odisha_Talcher_Coalfields_Talcher_-_OSPCB\Talcher_Coalfields_Talcher_-_OSPCB_2020.csv`
- `C:\Users\offrk\Desktop\cpcb\India CPCB\Odisha_Talcher_Coalfields_Talcher_-_OSPCB\Talcher_Coalfields_Talcher_-_OSPCB_2021.csv`
- `C:\Users\offrk\Desktop\cpcb\India CPCB\Odisha_Talcher_Coalfields_Talcher_-_OSPCB\Talcher_Coalfields_Talcher_-_OSPCB_2022.csv`
- `C:\Users\offrk\Desktop\cpcb\India CPCB\Odisha_Talcher_Coalfields_Talcher_-_OSPCB\Talcher_Coalfields_Talcher_-_OSPCB_2023.csv`
- `C:\Users\offrk\Desktop\cpcb\India CPCB\Odisha_Talcher_Coalfields_Talcher_-_OSPCB\Talcher_Coalfields_Talcher_-_OSPCB_2024.csv`
- `C:\Users\offrk\Desktop\cpcb\India CPCB\Odisha_Talcher_Coalfields_Talcher_-_OSPCB\Talcher_Coalfields_Talcher_-_OSPCB_2025.csv`