Goal: To extract landscape variables such as mean slope (given various radii from focal points), aspect ratio, or other topographical variables from digital elevation model (DEM). I am anticipating the following workflow, if possible:
- Import DEM into R
- Designate focal points for which landscape variables should be extracted
- Extract landscape variables
The DEM is 1-meter resolution for a 14.8km^2 island, so that's about 14 million points. I realize this would be quite sluggish in R, so I would also welcome suggestions for other tools (like SAGA, etc.).
Any good thoughts on this?
Why not using GRASS GIS, perhaps from inside R?
http://grasswiki.osgeo.org/wiki/R_statistics
There is an 'extract' function in the 'raster' package of R that would serve your purpose. You need to create the topographic variables' raster maps beforehand. Please consult the vignette: http://cran.r-project.org/web/packages/raster/raster.pdf. Hope that helps.
@ Damiano, @Avit, @ Alexandre. This is precisely what I was looking for. I've looked into "raster" and "rgdal" (and GRASS), but I wanted to make sure I'm on the right track. Many, many thanks for your assistance.
To all: I followed the suggestions here and successfully imported the DEM and extracted elevations and other variables for my focal points. I owe you all a beer (or coffee).
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