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SKILL.md
npx skills add isaaccorley/geospatial-skills --skill gdal
This skill should be used when working with GDAL command line tools for raster and vector geospatial processing. Covers inspection, reprojection, clipping, raster conversion, mosaics, tiling, rasterization, and COG creation.
npx skills add isaaccorley/geospatial-skills --skill gdal
Use GDAL command line tools for common raster and vector geospatial workflows.
Prefer the smallest tool that fits the task:
gdalinfoogrinfogdalwarpgdal_translategdalbuildvrtgdaladdogdaltindexgdal_rasterizegdal2tiles.pyogr2ogrIf GDAL is not installed, ask the user to install it before continuing.
One full gdalinfo dump on unknown data is worth it; after that, grep for the lines you need (Size is|Origin|Pixel Size|Band|Overviews|ID\[) — full WKT dumps are large. For vectors, -so -al prints the layer summary; bare -so without -al or a layer name prints nothing useful.
gdalwarp, gdal_translate, gdalbuildvrt, gdal_rasterize, gdal2tiles.pyogr2ogr, ogrinfo, gdaltindexUse the check that matches the operation — improvising verification is where runs go wrong:
gdaladdo on a writable GeoTIFF builds internal overviews; -ro forces an external .ovr sidecar — so the absence of a .ovr file next to the output proves the overviews are internal.
references/gdal-recipes.md (the only reference file)# Inspect
gdalinfo INPUT.tif
ogrinfo INPUT.shp -so
# Vector conversion and clipping
ogr2ogr -f GeoJSON -t_srs epsg:4326 OUTPUT.geojson INPUT.shp
gdaltindex -t_srs epsg:4326 -f GeoJSON OUTPUT_EXTENT.geojson INPUT_RASTER.tif
ogr2ogr -f GeoJSON -clipsrc OUTPUT_EXTENT.geojson OUTPUT_CLIPPED.geojson INPUT.shp
# Raster reprojection (choose -r intentionally: bilinear/cubic for continuous, near for categorical)
gdalwarp -t_srs EPSG:XXXX -tr XRES YRES -r bilinear -co TILED=YES -co COMPRESS=DEFLATE -co PREDICTOR=2 INPUT.tif OUTPUT.tif
# Raster clipping
gdal_translate -srcwin XOFF YOFF XSIZE YSIZE INPUT.tif OUTPUT.tif # by pixel window (exact, no resampling)
gdal_translate -projwin ULX ULY LRX LRY INPUT.tif OUTPUT.tif # by georeferenced bounds
gdalwarp -cutline INPUT.shp -crop_to_cutline -dstalpha INPUT.tif OUTPUT.tif # by polygon
# Raster conversion
gdal_translate -b 1 -b 2 -b 3 INPUT.tif OUTPUT.tif
gdal_translate -b 1 -b 2 -b 3 -of JPEG -outsize 400 0 INPUT.tif OUTPUT.jpg
# Mosaic and stack
gdalbuildvrt OUTPUT.vrt path/to/tiffs/*.tif
gdal_translate -co TILED=YES -co BIGTIFF=YES -co NUM_THREADS=ALL_CPUS -co COMPRESS=LZW -co PREDICTOR=2 OUTPUT.vrt OUTPUT.tif
# Internal overviews on an existing GeoTIFF (-r near for categorical; -ro writes external .ovr instead)
gdaladdo -r average OUTPUT.tif 2 4 8
# Rasterize and tile
gdal_rasterize -burn 1.0 -ot Byte -of GTiff -co COMPRESS=LZW -co BIGTIFF=YES INPUT.shp OUTPUT.tif
gdal2tiles.py -z 10-16 INPUT_BYTE.tif OUTPUT/
# COG (format-only conversion — smallest tool that fits)
gdal_translate -of COG -co COMPRESS=LZW -co PREDICTOR=2 -co NUM_THREADS=ALL_CPUS INPUT.tif OUTPUT.tif
# use gdalwarp -of COG only when also reprojecting in the same step
# Vector SQL: OGR's default dialect has no GROUP BY, window, or spatial functions —
# pass -dialect SQLite for anything beyond simple SELECT/WHERE
ogr2ogr -f GPKG OUT.gpkg IN.shp -dialect SQLite \
-sql "SELECT *, ST_Area(ST_Transform(geometry, EPSG)) AS area_m2 FROM layer WHERE landuse IN ('ag')" \
-t_srs EPSG:XXXX -nln layername