Dear All
I've got a raster map with a number of different patches (habitat blocks)
and need to calculate the shortest distance from the edge of each patch to
the edge of all other patches. Using r.volume (in combination with other
commands) is OK to calculate centroid distances, but not edge distances.
r.le.dist works only for one nearest patch (M4 option) or a specific group
(M9), not all patches. Any suggestions?
TIA
Roy
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Roy Sanderson
Centre for Land Use and Water Resources Research
Porter Building
University of Newcastle
Newcastle upon Tyne
NE1 7RU
United Kingdom
Tel: +44 191 222 7789
Fax: +44 191 222 6563
r.a.sanderson@newcastle.ac.uk
URL: http://www.cluwrr.ncl.ac.uk
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You could do a repetitive filter that runs on a layer containing patch
id's.
1) Get the patch id layer (PID)
2) grab the patch of interest into a new layer (INT)
3) Run a filter or a buffer to grow INT by one pixel (copy over INT)
4) Use INT as a mask to list patches in PID within INT, using r.stats
(PLIST)
5) Eliminate previously found patches from PLIST - New patches at that
distance.
6) Repeat 3-5 until a maximal buffer distance has been reached.
This approach will take a while, but it will work. I would advise doing
all of this through C code, rather than using the existing tools, but it
could all be done with some thought and the existing tools.
Good Luck,
Angus Carr. On Tue, 6 Jul
1999, Roy Sanderson wrote:
Dear All
I've got a raster map with a number of different patches (habitat blocks)
and need to calculate the shortest distance from the edge of each patch to
the edge of all other patches. Using r.volume (in combination with other
commands) is OK to calculate centroid distances, but not edge distances.
r.le.dist works only for one nearest patch (M4 option) or a specific group
(M9), not all patches. Any suggestions?
TIA
Roy
----------------------------------------------------------------------------
Roy Sanderson
Centre for Land Use and Water Resources Research
Porter Building
University of Newcastle
Newcastle upon Tyne
NE1 7RU
United Kingdom
Tel: +44 191 222 7789
Fax: +44 191 222 6563
r.a.sanderson@newcastle.ac.uk
URL: http://www.cluwrr.ncl.ac.uk
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