Horizon line of sight

[W6RZ]

Yes it is easy. It isn't measuring elevation of the land. It's measuring elevation of everything. I can see that it is measuring to the tree tops on my property. It shows a terrain difference of 75 ft across my driveway when the elevation of the land changes about 10 to 15 ft. That's because there are some tall thick trees at one end of the driveway. Maybe that's what it is supposed to do?

It depends on the elevation database. Radio Mobile uses a free database that was captured by the Space Shuttle with radar. So whatever reflects the radar signal the best will be what's recorded.

http://dds.cr.usgs.gov/srtm/

Radio Mobile website:

http://www.cplus.org/rmw/english1.html

Radio Mobile terrain database

http://www.cplus.org/rmw/dataen.html

[KA0GKT]

IIRC, a close approximation of the radio horizon (in Miles) can be calculated with the following equation: 1.415 x the square root of the antenna's center of radiation in Feet. (Multiply by 1.609 for km)