TechnicalGIS

Geospatial analysis you can run, check and reuse.

Step-by-step tutorials for GIS professionals. Every Python tutorial ships with the exact scripts we ran, and every map, chart and table on the page is the real output.

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Libraries covered GeoPandas · Shapely 2 · rasterio · rioxarray · pystac-client · OSMnx · Folium · pyogrio

Sentinel-2 true-colour image of Lake Mead on 7 September 2022: a narrow, branching blue-black reservoir in tan desert.
The same scene as an NDWI water index: water in blue, dry land in pale to deep red.
True colour B4 B3 B2 NDWI (B3−B8)/(B3+B8)
Lake Mead, Nevada–Arizona. Sentinel-2B L2A, 7 Sep 2022, tile 11SQA at 60 m. Open water by NDWI: 270.1 km², down 55.6 km² from August 2019. Drag the divider to compare. Reproduce this scene in Python
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Four rows of Sentinel-2 test chips. Each row shows the image, the reference labels, the U-Net prediction and the disagreement in magenta. The prediction matches rivers, woods and fields closely, but in the city centre it draws buildings as blobs instead of separate roofs.

Tutorial Python Part 2 of 3

U-Net satellite image segmentation in PyTorch: a TorchGeo and Sentinel-2 tutorial on a CPU

Train a U-Net to segment Sentinel-2 imagery into buildings, built-up land, trees, grass and water with PyTorch, segmentation_models_pytorch and TorchGeo's Sentinel-2 pretrained ResNet-18 weights, on a CPU in five minutes. Real loss curves, per-class IoU and F1, a confusion matrix and an honest look at what limits accuracy.

Advanced 12 min read

Map of central Bristol with 144,965 Overture building footprints coloured by subtype, most of them residential, and the River Avon in blue

Tutorial Python Part 1 of 2

Query Overture Maps with DuckDB spatial and GeoParquet in Python

Pull Bristol's 144,965 buildings and 20,727 places straight from the Overture Maps GeoParquet release with DuckDB, run spatial SQL joins and H3 aggregation, load the result into GeoPandas, write GeoParquet 1.1, and time it against Shapefile, GeoPackage and FlatGeobuf.

Intermediate 13 min read

Tutorial Python

InSAR ground subsidence in Python: one year of Mexico City sinking, from Sentinel-1

Map ground subsidence with Sentinel-1 InSAR in Python: stream 170 real interferograms of Mexico City, convert unwrapped phase to millimetres of line-of-sight motion, mask low coherence, invert a small-baseline network into a time series, and cross-check the velocity with MintPy.

Advanced 17 min read

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