[GRASS-user] centroid definition

GRASS GRASS user
1

hi list,

i would like to know how a centroid is defined and calculated. of course it is a
point within a closed boundary. but how is the position of the centroid
defined? is it estimated randomly? is it the point of gravity - but then - what
happens if the polygon is U-shaped?

thank you for helping
martin

2

Dear all,

Apologies if this has been covered before.

I have just installed Ubuntu7.04 as a VM using Microsoft virtual PC2007
(running under Vista x64 Ultimate). I downloaded the CVS and it compiled
without error. Indeed there appeared to be no errors during
installation. Grass62 starts fine and using the Spearfish60 dataset the
elevation rasters show without any problem. The problems start when I
invoke NVIZ (it does not matter whether I do this from the map window or
from the command line) - it says waiting and then it appears to do
nothing! I even let it 'wait' for 30 minutes but nothing appeared.

It is sometime (nearly a year) since I last tried to use grass - am I
overlooking something simple?

Thanks

Darrel

Prof Darrel Maddy
Chair of Quaternary Science
University of Newcastle, UK
http://www.ncl.ac.uk/geps/staff/profile/darrel.maddy

3

On Friday 19 October 2007, Darrel Maddy wrote:

Dear all,

Apologies if this has been covered before.

I have just installed Ubuntu7.04 as a VM using Microsoft virtual PC2007
(running under Vista x64 Ultimate). I downloaded the CVS and it compiled
without error. Indeed there appeared to be no errors during
installation. Grass62 starts fine and using the Spearfish60 dataset the
elevation rasters show without any problem. The problems start when I
invoke NVIZ (it does not matter whether I do this from the map window or
from the command line) - it says waiting and then it appears to do
nothing! I even let it 'wait' for 30 minutes but nothing appeared.

It is sometime (nearly a year) since I last tried to use grass - am I
overlooking something simple?

Probably something realted to how the VM arbitrates access to the video
hardware - esp. with regards to OpenGL... try googling for related things?

Dylan

Thanks

Darrel

Prof Darrel Maddy
Chair of Quaternary Science
University of Newcastle, UK
http://www.ncl.ac.uk/geps/staff/profile/darrel.maddy

_______________________________________________
grassuser mailing list
grassuser@grass.itc.it
http://grass.itc.it/mailman/listinfo/grassuser

--
Dylan Beaudette
Soil Resource Laboratory
http://casoilresource.lawr.ucdavis.edu/
University of California at Davis
530.754.7341

4

Hi Dylan,

Actually turned out to be me being stupid! The VM emulates an S3 trio
video card with no OpenGL hardware. Once I removed the reference to my
Nvidia opengl drivers (silly me) and replaced them with the Mesa
emulators everything now seems to be fine.

Best wishes

Darrel

-----Original Message-----
From: Dylan Beaudette [mailto:dylan.beaudette@gmail.com]
Sent: Friday, October 19, 2007 5:47 PM
To: grassuser@grass.itc.it
Cc: Darrel Maddy
Subject: Re: [GRASS-user] NVIS problem

On Friday 19 October 2007, Darrel Maddy wrote:

Dear all,

Apologies if this has been covered before.

I have just installed Ubuntu7.04 as a VM using Microsoft virtual
PC2007 (running under Vista x64 Ultimate). I downloaded the CVS and it

compiled without error. Indeed there appeared to be no errors during
installation. Grass62 starts fine and using the Spearfish60 dataset
the elevation rasters show without any problem. The problems start
when I invoke NVIZ (it does not matter whether I do this from the map
window or from the command line) - it says waiting and then it appears

to do nothing! I even let it 'wait' for 30 minutes but nothing

appeared.

It is sometime (nearly a year) since I last tried to use grass - am I
overlooking something simple?

Probably something realted to how the VM arbitrates access to the video
hardware - esp. with regards to OpenGL... try googling for related
things?

Dylan

Thanks

Darrel

Prof Darrel Maddy
Chair of Quaternary Science
University of Newcastle, UK
http://www.ncl.ac.uk/geps/staff/profile/darrel.maddy

_______________________________________________
grassuser mailing list
grassuser@grass.itc.it
http://grass.itc.it/mailman/listinfo/grassuser

--
Dylan Beaudette
Soil Resource Laboratory
http://casoilresource.lawr.ucdavis.edu/
University of California at Davis
530.754.7341