Raster aggregate values: Difference between revisions
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(new, based on Hamish's notes) |
(or r.resamp.stats) |
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* Draw a 1 km x 1 km grid ({{cmd|d.grid}}), and overlay the {{cmd|v.mkgrid}} vector map (area fill = none, or only display boundary features, colored red or so) just to verify where it will be and what it will look like. | * Draw a 1 km x 1 km grid ({{cmd|d.grid}}), and overlay the {{cmd|v.mkgrid}} vector map (area fill = none, or only display boundary features, colored red or so) just to verify where it will be and what it will look like. | ||
* Run {{cmd|v.rast.stats}} to calculate stats for each grid box, and upload to that area's attribute table. | * Run {{cmd|v.rast.stats}} to calculate stats for each grid box, and upload to that area's attribute table. | ||
''Perhaps a similar thing could be done using {{cmd|r.resamp.stats}}?'' | |||
[[category: FAQ]] | [[category: FAQ]] | ||
Revision as of 09:46, 26 August 2010
Q: How can I calculate the average map values by spatial unit (grid)? For example, I would like to calculate the average slope by square kilometer for a given area.
A: Procedure outline:
- Make a slope map from the DEM with r.slope.aspect at the same resolution and bounds as the DEM. (run 'g.region rast=dem' first)
- Make the grid with v.mkgrid, with box=1000,1000 (assuming the location is meters-based)
- Draw a 1 km x 1 km grid (d.grid), and overlay the v.mkgrid vector map (area fill = none, or only display boundary features, colored red or so) just to verify where it will be and what it will look like.
- Run v.rast.stats to calculate stats for each grid box, and upload to that area's attribute table.
Perhaps a similar thing could be done using r.resamp.stats?