| Re: Display of topo map in MAP routines. [message #68039 is a reply to message #68038] |
Tue, 22 September 2009 13:39   |
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Paul Van Delst[1]
Messages: 1157
Registered: April 2002
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Senior Member |
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David Fanning wrote:
> Paul van Delst writes:
>
>> Can someone outline (real quick) the steps needed to display a topo map in the background
>> of a map projection? Other point data will be overplotted over this background.
>
> Do you really mean "topo map"? If you do, I'm not sure
> there *is* a quick way to do this. Maybe if you could
> get ahold of a digital topo map in GeoTIFF format you
> might be OK. But even the smallest topo map is going to
> be HUGE and difficult to work with. I have a topo map of
> Canyonlands National Park in front of me on the wall.
> It's about 3 by 4 feet. I hate to think what size it would
> be in digital format. :-(
>
>> Does a DEM file come with IDL, or do I need to visit the USGS?
>
> IDL does not come with a DEM file. Is this what you
> mean by a "topo map"?
>
> Maybe you could clarify what you are trying to do,
> including some explanation of the tools you plan to
> use. I have a feeling you are asking about building
> a 18,000 sq ft dream home, but have the plans for a
> dog house in front of you. :-)
If I grok the analogy correctly, I think I mean the opposite. I'll be quite happy with the
doghouse version. :o)
But I did mean a digital elevation map (i.e. lat, lon, height). A colleague supplied the
GTOPO30 DEM data from the USGS and I bumbled my way through to actually displaying the
elevation data on a map (yay!).
I was trying to avoid the hassle of writing code to read the DEM file - but it ended up
being relatively simple. Once I have x, y, and z data in IDL I can figure out how to
display stuff by browsing your site and my books -- it was getting said data from disk
file to IDL variable that I was being lazy about. I thought there was some well know-about
file with an object reader in IDL (at least, to the DEM/IDL cognoscenti) but I guess not.
Sorry for the newsgroup noise...
cheers,
paulv
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