On Sat, 3 Mar 2012 04:02:49 +0000 (UTC), alpha male
wrote:

What elevation tool do you use and how does it compare in accuracy?

I'm trying to do some antenna siting calculations ... and ... for
that ... I need elevation information.

However ... given any set of coordinates ... e.g., Mt Hamilton,
California at coordinates 37.337408,-121.644073 ... I find the following
elevation tools all give DIFFERENT elevations (some are off by more than
a hundred feet!)

1. Google Map API yields 1217.061889648438 meters (3992.985 feet)
http://maps.googleapis.com/maps/api/elevation/json?
locations=37.337408,-121.644073&sensor=false

2. Geoplaner yields 1217.1 meters (3993 feet)
http://www.geoplaner.com

2. Daftlogic yields 1230.988 meters (4038.676 feet)
http://www.daftlogic.com/sandbox-goo...d-altitude.htm

4. Earthtools yields 1210 meters (3969.8 feet)
http://www.earthtools.org

5. Heywhatsthat (SRTM db) yields 1213 meters (3980 feet)
http://www.heywhatsthat.com/profiler-0904.html

Q: Which elevation tool do you use ... & what's the accuracy?

Youre asking wrong questions.
First define a surface with height ZERO as a reference.
There are about 100 different definitions alone for that.
Distance from Earth center, median sea level at Novosibirsk,
or a San Francisco? Water isn't level, it follows gravitation.
And so on.

w.