Hello all,
thanks for the ideas on alpha transparency application. Finally I converted all outputs to pnm and pgm (using PerlMagick) and applied a pnmcomp command and then converted it back to png. Works, great, thanks!
Now I have two more questions. Actually I am a computer sciences student and don't have any experience in GIS and physical geography in general. I am slowly discovering Grass and find it excellent (also for its perfect usage of linux command line).
I wanted to display a map of Germany (5E-16E, 47N-56N) using Universal Polar Stereographic projection and wgs84 ellipsoid, but it is still wider than higher. I tried the lat-lon projection before, but the result was the same. Actually, on most commercial general maps of Germany, the country is "almost the same wide as tall", while all these projections show it much wider. Which projection/ellipsoid would you recommend for usage on such location as Germany? Or is there any other way to stretch the output vertically/horizontally apart from scaling the output png file?
Another question concerns the colours. For raster maps, I can use the r.colors command and the "rules" colorset where I define some colours for some fixed values and the rest is interpolated. Is there any way to define such rules and then use d.vect.area with some value, so that the fillcolor is taken from the rules table?
Thank you very much for your help,
Miroslav Sedivy
____________________________________________________________
Miroslav Sedivy http://www.slovensko.com
miro@slovensko.com ... Your Guide to Slovakia
Hello all,
I wanted to display a map of Germany (5E-16E, 47N-56N) using Universal
Polar Stereographic projection and wgs84 ellipsoid, but it is still wider
than higher. I tried the lat-lon projection before, but the result was the
same. Actually, on most commercial general maps of Germany, the country is
"almost the same wide as tall", while all these projections show it much
wider. Which projection/ellipsoid would you recommend for usage on such
location as Germany?
Have you tried Gauss-Krüger ?
Another question concerns the colours. For raster maps, I can use the
r.colors command and the "rules" colorset where I define some colours for
some fixed values and the rest is interpolated. Is there any way to define
such rules and then use d.vect.area with some value, so that the fillcolor
is taken from the rules table?
AFAIK, there are no such "automatic" rules for d.vect.area, so you have to
define the legend file yourself.
Moritz
Well from earlier questions that have gone unanswered - I guess no one is
using grass with digitizing tablets. So I will try another tack. I want to
use Grass in preference to ArcView, MapInfo, ... but have one all-consuming
issue. How to make polygons. Thought I had it when I explored v.in.dxf.
Unfortunately Grass does not make polygons out of dxf files only line or
point features. Have been trying to find a way in Grass to convert closed
polylines to polygons using v.support and v.build.polylines. No luck so
far. Have spent way too much time searching the web and going over man
pages.
Don't have much hair left to pull out. Can anyone suggest a method to make
polygons in Grass or in files imported from Cad programs??
Well from earlier questions that have gone unanswered - I guess no one is
using grass with digitizing tablets. So I will try another tack. I want
to
use Grass in preference to ArcView, MapInfo, ... but have one
all-consuming
issue. How to make polygons. Thought I had it when I explored v.in.dxf.
Unfortunately Grass does not make polygons out of dxf files only line or
point features. Have been trying to find a way in Grass to convert closed
polylines to polygons using v.support and v.build.polylines. No luck so
far. Have spent way too much time searching the web and going over man
pages.
Don't have much hair left to pull out. Can anyone suggest a method to
make
polygons in Grass or in files imported from Cad programs??
In the GRASS ascii vector file all that distinguishes lines from polygons
are the 'L', respectively 'A' label. So "all" you have to do is change
those. There is a script in GRASS called v.line2area which should be able
to do this for you.
Moritz
there's a shell script, v.line2area, which I think does this
Nick Cahill
On Tuesday, March 25, 2003, at 10:26 AM, John Doucette wrote:
Well from earlier questions that have gone unanswered - I guess no one is
using grass with digitizing tablets. So I will try another tack. I want to
use Grass in preference to ArcView, MapInfo, ... but have one all-consuming
issue. How to make polygons. Thought I had it when I explored v.in.dxf.
Unfortunately Grass does not make polygons out of dxf files only line or
point features. Have been trying to find a way in Grass to convert closed
polylines to polygons using v.support and v.build.polylines. No luck so
far. Have spent way too much time searching the web and going over man
pages.
Don't have much hair left to pull out. Can anyone suggest a method to make
polygons in Grass or in files imported from Cad programs??
Whoa. That was quick!
Thanks to both responders. A quick trial was successful.
That should be a huge help.
John