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National Elevation Dataset

PostPosted: Mon Sep 28, 2009 10:26 am
by JoeGrim
I'm writing a comprehensive guide book on the trails and peaks of the Comanche Peak Wilderness Area, and I'm hoping to include an overview map showing all the trails overlaid on a custom elevation contour map. I have found that I can download the National Elevation Dataset (NED) files for any area at seamless.usgs.gov/index.php, but it's in a format that I'm unfamiliar with. I was wondering if anyone knew of a program that can convert these NED files into a more common format? I'm not a computer guru, but if I can get it into a simple format like binary or ascii, then it will be no problem for me to make the map I want. Any input would be greatly appreciated.

Re: National Elevation Dataset

PostPosted: Wed Sep 30, 2009 6:21 pm
by TWorth
Never seen ASCII NED files. Raster formats such as the ones on the seamless site are standard for DEM data these days. ASCII elevation files can be made by loading one of the raster formats into a GIS viewer such as Arcview, loading an ASCII file of geographic coordinates and then exporting elevations. What you end up with is a ASCII file with a list of coordinates and the elevation at each coordinate. The exact steps depend on which viewer you are using. I did the steepness measure stuff using Globalmapper v7.0 and BIL(bitwise interleaf) format for the viewer.

If you just need a relief map to superimpose trails/routes onto any viewer can produce that from the formats on the seamless site. A given area can be saved as an image file and then overwritten with mspaint, etc.

Hope this helps...The guidebook sounds neat. -Tim

Re: National Elevation Dataset

PostPosted: Thu Oct 01, 2009 11:03 am
by JoeGrim
Thanks for the help, Tim. I tried Global Mapper and it's pretty neat. I like how I can make my own colored elevation scale. However, I can't export anything since I don't want to purchase the license. Do you know of any freeware or shareware that I can use to output ascii data or make very high publication-quality elevation plots?

Re: National Elevation Dataset

PostPosted: Thu Oct 01, 2009 4:10 pm
by TWorth
Hey Joe - There are(or were) registration codes for older versions of Globalmapper floating around on the internet. I never found a good free GIS viewer that could do the export thing, though there might be one out there. A while back I was going to write a program to extract elevations from .BIl file(given the coordinates) so that it wouldn't be neccesary to load all the data and coordinate files into globalmapper, which takes quite a while for large areas like whole states. Never got around to it.

Re: National Elevation Dataset

PostPosted: Thu Oct 01, 2009 4:55 pm
by John Kirk