>There is a fairly easy way to generate terrain profile maps
>for your QTH. It uses free USGS DEM maps and a free
>program called MicroDEM written by Peter Guth of the
>U.S. Naval Academy. I've written an article on how to
>do this and the ARRL is publishing it in the next Antenna
>Compendium scheduled for publication this fall. Dean
>Straw (N6BV, author of YT and ARRL editor) and I are
>working on the final editorial revisions now. Pete Smith,
>N4ZR, has also been involved in the review efforts. This
>enhances everyone's ability to use Pete's method of
>"Scoring" antenna's since multiple terrain profiles can
>easily be made.
>
>Using MicroDEM you can generate a terrain profile from
>any location at 1 degree increments for 10 foot intervals
>of in less than 10 minutes from sitting down at your
>computer. Of course that's after you've done a few
>things like installing the software, combined the DEM
>maps and learned the program a bit.
>
>With very little work MicroDEM can also tell you things like
>line-of-sight coverage for UHF/VHF communications, distance
>between stations, true north for any location in the world, height
>for antenna's to have line of sight between to fixed points, and
>projected flood plane levels for those of you involved in emergency
>communications.
>
>MicroDEM can also merge DEM files for multiple area's so if you
>find you live next to an edge of a USGS map you can still use it
>to get accurate terrain profiles. Dean did find that in some locations
>this feature doesn't work correctly and is working with the USGS and
>Professor Guth on why not.
>
>Unfortunately the free maps available seem to be pretty much limited
>to the U.S. That's probably because they're put out by the U.S.
>government.
>
>If you want to use it, do a web search for MicroDEM and download it.
>It's pretty big -- around 30 mB. Read the help file about how to use
>the program. Pay particular attention to inputting your latitude and
>longitude, calculating "offset", and how to make a "stream profile".
>What I did was selected my location on the map and then calculated
>an offset distance (say 10,000 feet) and a bearing (say 40 degrees).
>Then followed the directions to show a "stream profile" for that offset
>by using the starting and ending points of the offset. You'll be given
>a graphical representation of the "stream profile" but MicroDeM allows
>you to download the data used to generate it. That data can be
>converted manually into an ASCII file for input to YT or TA. I used
>Excel originally, but Dean wrote a short program to do it automatically.
>
>If you don't want to figure it out using the above information again, the
>article should be published this fall. Since the ARRL has publishing
>rights to the article I'll check with them and find out if I can give more
>information or not. This should at least give some of you a good start
>and save you a lot of work!
>
>You can get the DEM files for your area from the USGS website at
><http://www.gisdatadepot.com/dem/demdownload.html>http://www.gisdatadepot.com/dem/demdownload.html
>
>
>Kevan Nason
>NS4T
>knason@ e m e r a l d i s . c o m
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