[GRASS-user] finding distance to raster features in a given direction

[Nick Gauthier]

Hi,

Given a binary land/sea raster, I’m trying to calculate the shortest
distance from each land cell to the sea within a range of wind directions
(e.g. 85-95 degrees from north). The calculation is basically
r.grow.distance with an extra parameter for the range of directions (or a
raster of the input bearings at each cell) with which to restrict the
spreading function.

I’d appreciated any advice on how to to implement something like this in
GRASS.

I have an implementation in R that draws a line from each cell along the
given bearing and finds the length of the segment that intersects with a
land polygon (vectorized from the land/sea raster). This is slow for larger
rasters and doesn't apply to a range of directions, so it looks like
something closer to r.grow.distance is the way to go.

Thanks for any suggestions,
Nick

*Nicolas E. Gauthier*
Graduate Research Assistant, Center for Social Dynamics and Complexity
School of Human Evolution and Social Change
Arizona State University
Nicolas.Gauthier at asu.edu
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