[Gdal-dev] shaded relief utility

[Ethan Alpert]

Well I used NCAR Graphics, however there's no way to get the contours
out of NCAR Graphics. Hence my earlier email asking if anyone has seen
utilities for closed vector contours. Nearly every contouring
application I've found does not produce closed polygons but just iso
lines except NCAR Graphics. Unfortunately NCAR Graphics output is a CGM
metafile.

They do have a way of dumping text from the CGM file which I've written
a perl script to parse and create a shapefile but the shapefile is still
in the CGM's integer coordinate system. Even so this is all more steps
than there should be.

-e



-----Original Message-----
From: Bryan Keith [mailto:bryan at geomega.com] 
Sent: Tuesday, December 13, 2005 1:47 PM
To: Ethan Alpert
Cc: gdal-dev at lists.maptools.org
Subject: Re: [Gdal-dev] shaded relief utility


Ethan Alpert wrote:

>One way to accomplish this is to color a vector topo set and overlay it

>with partial transparency over a grey scale hill shade relief.
>
>  
>
Ethan,

How do you create the vector topo set from the DEM?

That's essentially the question I asked to a couple gis lists (though 
not this one) a few weeks ago, and I didn't get any answers.  The output

must be closed polygons attributed with the data range of the DEM that 
the polygon encloses, and the polygons must look like the results of a 
contouring algorithm, not along the jagged cell edges of the input data,

just like the dataset on the demis website.

Bryan

>I believe this is how demis does it. Check out the map server below. 
>Turn off all layers except hillshading and topography. Zoom in to an 
>area and toggle one of those two layers. You'll see what I'm talking 
>about.
>
>http://www.demis.nl/home/pages/wms/demiswms.htm
>
>-----Original Message-----
>From: gdal-dev-bounces at lists.maptools.org
>[mailto:gdal-dev-bounces at lists.maptools.org] On Behalf Of Paul Surgeon
>Sent: Tuesday, December 13, 2005 1:04 PM
>To: Brent Fraser
>Cc: gdal-dev at lists.maptools.org
>Subject: Re: [Gdal-dev] shaded relief utility
>
>
>On Monday 12 December 2005 23:32, Brent Fraser wrote:
>  
>
>>Paul, Matt,
>>
>>  And it compiled ok on Windows.  I justed editted the makefile.vc
>>file to include hillshade.exe.  I haven't actually tried it yet.
>>
>>  Like Paul,  I'm actually interested in shading an image file based
>>on a DEM (if that's what you meant, Paul)
>>
>>Brent
>>    
>>
>
>No, I meant I need a way to make "color scaled relief maps" (or 
>whatever they are called in GIS lingo) from DEMs. The type that has a 
>color gradient based
>on the altitude.
>
>It's pretty simple so I find it hard to believe no one has written an 
>open source utility to do it. It's just a matter of trying to find out 
>what's
>
>available.
>
>I take it what you're after is a way to modulate an existing base image

>with a hillshade image generated from a DEM.
>
>Paul
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>  
>