[winGRASS] RE: average slope for a polygon?

[Mike Thomas]

Hi Jeff.

I'm cc'ing to the main Grass list in case the memory problem is a known
Grass bug on other platforms.  It may also have been fixed in the current
Grass sources.  If this brings you no joy, please send me the data or
provide a download site, along with precise instructions on the Grass side
of things (I don't have Arc/Info) so that I can try and reproduce the
problem.

Likewise someone may be able to help in relation to your question on
multiple attributes.

In relation to ODBC on Windows Grass, I am not aware of anyone having done
it yet.  It would be a shame to have to use UNIXODBC however.

As far as I know, there is not yet a publicly available build of 5.0.0 using
XFree86 for Cygwin (Any further news Malcolm?).  There is a native build
however, at:

  http://grass.itc.it/grass5/binary/windows_cygnus/wingrass_generic/

It is more limited than the XFree86 version (no NVIZ, no TCLTK-grass) but is
fine for most tasks such as the data conversion you are doing below.

Cheers

Mike Thomas.

-----Original Message-----
From: wingrass-admin at grass.itc.it [mailto:wingrass-admin at grass.itc.it]On
Behalf Of Jeff D. Hamann
Sent: Saturday, January 04, 2003 4:59 AM
To: wingrass at grass.itc.it
Subject: [winGRASS] average slope for a polygon?


I have been trying to get the average slope for a polygon (actually all the
polygons) for a vector file created from r.poly from a classified satellite
image and I've just run out of steam. I've exported the slope file
(generated from r.slope.aspect) into arc/info and converted the grid to
points and exported the points (of course you have to export the ungenerate
file and the attribute file as two separate files then link them together
after importing them into access! ugh). It's the same process as simply:

r.to.sites -z input=slp30.testshed.rast output=slp30.testshed.site
s.out.ascii -di sites=slp30.testshed.site fs=, >slope.points.out

which would have been much better (expect for the ERROR: G_malloc: out of
memory message I kept getting with GRASS 5.0.0.pre3 on cygwin). I then have
to read this file in and compute the average slope for each of polygons. Is
there a way to do this in GRASS?

And more questions...

1) has anyone found decent docs on getting odbc to work with grass under
cygwin (do we have to use unixodbc or win32 odbc?)
2) what's the story on getting "native" multiple attribute support on any
version of grass 5.0/5.1?
3) is there a version of grass5.0.0 for cygwin yet? not one of the
pre-release version.

I would really love to turn arc/info all together but can't just yet. keep
up the great work.

Jeff.

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