Newsgroups: info.grass.user
Path: zorro.cecer.army.mil!shapiro
From: shapiro@zorro.cecer.army.mil (Michael Shapiro)
Subject: Re: raster_to_vector
Message-ID: <C2557L.84F@news.cecer.army.mil>
Sender: news@news.cecer.army.mil (Net.Noise owner)
Organization: US Army Corps of Engineers Construction Engineering Research Labs
References: <9302011859.AA03975@vinny.cecer.army.mil>
Date: Mon, 8 Feb 1993 17:42:57 GMT
Lines: 45
In <9302011859.AA03975@vinny.cecer.army.mil> feeney@vinny.cecer.army.mil (Bob Feeney) writes:
Just a note: copying GRASS files with g.copy does NOT resample or
zoom. If you want to resample (or zoom) raster maps, use r.resample.
At present there is no complimentary function for resampling or zooming
vector maps.
r.poly doen't preserve the catgegory labels. This is an oversight, but
it has not been fixed in the beta release for 4.1. The simplest
workaround is to use the UNIX cp(1) command to copy the raster category
file (under cats/) to the vector category file (under dig_cats/). That
will be a lot easier that typing it all in by hand with v.support. You
might start with v.support and create "dummy" category file and then do
the copy. I don't recommend this generally, since GRASS category
structures may evolve to the point where this won't work, but it will
work for 4.0 and 4.1.
I have reported the lack of category info from r.poly to
grassbug@zorro.cecer.army.mil.
After running r.poly you have to run v.support, first (1) to
build topology and then second (2) to create category support.
In v.support (2) you have to designate how many categories are
needed so you have to know what the highest category value
of the raster file was. Enter this number and then hit ESC.
You now have to manually enter the category descriptors, if
you need to show more than just the category number. If you
have many categories it is best to run r.cats to list them
prior to running v.support.
You can copy a portion of a file by first using d.zoom to
designate the new "region" and then copying the file. It
should only copy that portion of the file.
If you have any more specific questions or run into any problems
you can e-mail or even call at (217) 373-4420 ext. 320.
Good Luck.
Bob
--
Michael Shapiro U.S. Army CERL
Environmental Division