I would like to collect a table of equivalent or close enough gdal based functions to replace ArcGIS functions (esp in spatial analyst). Are there functions available using gdal to perform the following ArcGIS functions:
- Lookup
- Zonal statistics
- Focal statistics
- Nibble
- Iterate through raster VAT
- Combine
- Mosaic
The key is to have a ready reckoner of such functions, so ArcGIS based code can be relatively painlessly changed to one based on gdal.
Answer
In addition to Micha's list, here is how you can nibble with GRASS
1) mask your image with r.mapcalc
2) with the resulting image, interpolate to the nearest neighbour using r.surf.nnbathy
For combine, I would use r.cross but you can also do it using r.mapcalc with this algorithm
For mosaic, I would use gdalbuildvrt: it is often not necessary to create a new file, and you can translate it after if it becomes necessary.
As mentioned by @webrian, r.reclass can be used for lookup.
VAT's are tables, so you can use table editing tools to update them (see e.g. this post)
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