Gary,
Message: 2
Date: Mon, 22 Feb 2010 05:00:09 -0800 (PST)
From: Gary Nobles <garynobles@yahoo.com>
Subject: [GRASS-user] Re: calculating maximum and minimum diameters
with, GRASS or R and GRASS?
To: grass-user@lists.osgeo.org
Message-ID: <1266843609307-4611842.post@n2.nabble.com>
Content-Type: text/plain; charset=us-asciiIs 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