GeoKolam research data

GIS and on-device remote sensing tests of GeoKolam

Data and analysis scripts for a study of GeoKolam, the free Android GIS from ArcGX TechLabs Private Limited. The study tests the app's measurement, file formats and vector tools on the 38 district boundaries of Tamil Nadu from TNGIS, and its on-device satellite maps over Tiruchirappalli district against a 10 m reference made with GDAL.

Author Suneel Bose K, Founder and CEO, ArcGX TechLabs Private Limited, Tiruchirappalli
Status Under consideration, 2026
App version GeoKolam 1.2.0

Get GeoKolam on Google Play ORCID Downloads

Key results

All numbers come from logged runs. The logs are in the results and scripts download.

1.1 × 10⁻¹²Largest relative difference between the app's geodesic district areas and Karney's algorithm in PROJ

1.4 mmLargest vertex shift when GDAL read the app's exports in six formats, with Tamil names intact

52 MBDownloaded to make eleven maps of the 4,490 km² district on the device; all were rebuilt offline

0.004Largest difference in district mean NDVI between the app's 80 m maps and the 10 m reference

Maps made by the app

Tiruchirappalli district from Sentinel-2B passes on 13 December 2025 and 3 March 2026, at 80 m cells, as the app rendered them. NDVI fell from 0.60 to 0.39, mostly on cropland after the Samba rice harvest.

False colour map of Tiruchirappalli district on 13 December 2025, with vegetation in red — False colour, 13 December 2025

NDVI map of Tiruchirappalli district on 13 December 2025, mostly dark green — NDVI, 13 December 2025

NDVI map of Tiruchirappalli district on 3 March 2026, mostly light green and yellow — NDVI, 3 March 2026

NDVI change map of Tiruchirappalli district from December to March, mostly red for loss — NDVI change, March minus December

Downloads

Each download is a zip file with a short readme inside.

Results and analysis scripts 0.1 MB

Result logs for every run, the 10 m reference results, the summary tables and the Python scripts for the reference, the checks and the figures.

Tiruchirappalli Sentinel-2 maps 20.0 MB

Eight GeoTIFFs made by the app at 80 m in UTM zone 44N: NDVI and NDWI for both dates, NDVI change, false colour for both dates and true colour for December.

Tiruchirappalli terrain and land cover maps 7.7 MB

Elevation and slope at 60 m from the Copernicus DEM and land cover at 80 m from ESA WorldCover 2021, made by the app.

District exports: Shapefile, GeoJSON, CSV and KML 16.3 MB

The 38 TNGIS district boundaries written by the app's own exporters, with English names, Tamil names and LGD codes.

District exports: GPX and DXF 10.6 MB

The same boundaries as GPX tracks of the outer rings and as DXF polylines in UTM zone 44N.

Vector tool outputs 7.5 MB

GeoJSON outputs of the app's vector tools run without GEOS: centroids, convex hulls, simplification, fishnet, clipping, random points and point counts.

Data sources

District boundaries: Tamil Nadu Geographical Information System (TNGIS), Tamil Nadu e-Governance Agency, published for public use.
Sentinel-2 Level-2A: Cloud Optimized GeoTIFFs on the Registry of Open Data on AWS. Contains modified Copernicus Sentinel data 2025 and 2026.
Elevation: Copernicus DEM GLO-30, doi.org/10.5069/G9028PQB.
Land cover: ESA WorldCover 2021 v200, doi.org/10.5281/zenodo.7254221, CC BY 4.0.

GeoKolam's source code is proprietary to ArcGX TechLabs Private Limited and is not published. The test programs that run the app's own code depend on it, so they are not published either. Their results are in the logs above.

How to cite

Suneel Bose K. (2026). GeoKolam research data: GIS and on-device remote sensing tests in Tamil Nadu and Tiruchirappalli district [Data set]. ArcGX TechLabs Private Limited. https://www.bosekarmegam.in/research/geokolam/