000000000000000000000000 222233333333333333444444 111000000000000000000000 111222222222223333333333 000111111111100000000000 222111111111122223333333 000000001000011100000000 332222221222211122222222 000000001000000011111111 333333321233222211111111 000000001000000000000000 433333321233333222222222 000000001000000000000000 444443321233333333333333 000000001000000000000000 444443321233443333333333 000000001000000000000000 444443321233444444444444 Category 0: No roads Category 1: Road location Category 2: Buffer Zone 1 around roads Category 3: Buffer Zone 2 around roads Category 4: Buffer Zone 3 around roads
Distances from cells containing the user-specified category values are calculated using the "fromcell" method. This method locates each cell that contains a category value from which distances are to be calculated, and draws the requested distance rings around them. This method works very fast when there are few cells containing the category values of interest, but works slowly when there are numerous cells containing the category values of interest spread throughout the area.
r.buffer measures distances from center of cell to center of cell using Euclidean distance measure for planimetric locations (like UTM) and using ellipsoidal geodesic distance measure for latitude/longitude locations.
r.buffer calculates distance zones from all cells having non-NULL category values in the input map. If the user wishes to calculate distances from only selected input map category values, the user should run (for example) r.reclass prior to r.buffer, to reclass all categories from which distance zones are not desired to be calculated into category NULL.
The -z flag can be used to ignore raster values of zero instead of NULL values in the input raster map.
When working with massive raster regions consider the r.buffer.lowmem module if RAM use becomes a problem. The lowmem version can be > 40x slower, but will work with minimal memory requirements. The classic r.buffer should be able to deal with raster maps of 32000x32000 size on a system with 1 GB RAM, and rasters of 90000x90000 on a system with 8 GB RAM without going into swap.
g.region raster=roadsmajor -p r.buffer input=roadsmajor output=roadsmajor_buf distances=100,200,300,400,500
r.category input=roads.buf 1 distances calculated from these locations 2 0-100 meters 3 100-200 meters 4 200-300 meters 5 300-400 meters 6 400-500 meters
Last changed: $Date: 2016-01-21 03:10:11 -0800 (Thu, 21 Jan 2016) $
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