On Sat, 03 Mar 2012 19:43:47 -0800, Jeff Liebermann wrote:
What is the OP trying to accomplish?

The neighbors and are discussing setting up a neighborhood mesh network
and we need to ascertain, beforehand, where to place masts and which
direction to point them in our mountainous neighborhood (Skyline & Summit
area).

If for an FCC license HAAT calculation, almost any reasonable guess
will suffice.

For us, probably any reasonable answer would suffice - but why not pick
the most accurate for starters is what we're thinking.

What level of accuracy is really required?
The original position of 37.337408N -121.644073W is specified
to 1 millionth of a degree, or about 0.09 meters.

A few feet would probably work just fine for the neighborhood. We each
have acres of land, but the terrain is so rough that only a few spots for
antennas would be useful. That's why we want to choose them ahead of time.

It would be interesting to know where this highly accurate
number came from.

We didn't want to put our actual location on the net, so, we picked an
arbitrary set of numbers from one of the elevation calculators just as an
example. But we're in the roughly 37,-122 range.

What datum are you using? I suggest WGS84.

WGS84.

We have some numbers in NAD83 from the various WISP providers but they
drive us crazy since we have to imperfectly convert them to WGS84 to keep
our numbers consistent.

Are you interested in ground level, building rooftop level,
or tree top level?

All three because we want to site a dozen or more antennas which need to
have clear line of sight over rooftops and trees by at least the first
Fresnel zone.