Gary,
Message: 2
Date: Mon, 22 Feb 2010 05:00:09 -0800 (PST)
From: Gary Nobles <[email protected]>
Subject: [GRASS-user] Re: calculating maximum and minimum diameters
with, GRASS or R and GRASS?
To: [email protected]
Message-ID: <[email protected]>
Content-Type: text/plain; charset=us-ascii
Is there no simpler way? e.g using the centroid as a center spot and then
find the part of the polygon which is furthest away and use that distance
for max radius? (and min dist for min radius)
or make grass create a circle increasing in size untill it is fully outside
the polygon then use that radius?
Is this beyond GRASS? There must be a way using R - although I am still
learning so I would be greatful of any instructions of how to do this in R
(including which libraries to use) I may have to go to a R forum, any good
ones?
There are a few approaches that occur to me. One thing I think you'll
need is a map showing just the centroid locations (as points). You can
do this by using v.extract, eg:
v.extract <input map> output=<output map> type=centroid
Then you could use v.distance measure distance from the centroids to all
the boundaries in the original map, capture this in a database table,
and select the min and max associated with each centroid.
A question for others in the list: if you use the -a flag in v.distance,
from centroid to line, I presume the measurement from the centroid is to
all nodes on the line?
Richard
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