On 3/3/2012 7:59 AM, alpha male wrote:
On Sat, 03 Mar 2012 00:10:32 -0800, miso wrote:
Have you considered running SPLAT!

I just installed the Splat (Surface Path Length And Terrain) RF analysis
application (version 1.3.0-1) from the default Ubuntu Software Center.
- http://joysofprogramming.com/install-splat-ubuntu/
- $ sudo apt-get install splat (dpkg -s splat)

It's apparently a command-line tool which needs me to download the
database so it may take a while to figure out.

Googling for a "splat!" tutorial, I find it's also a photoshop hack so
it's actually hard to figure out how to use it on the fly.

Q: Do you have a working example or two for how to use it from the
command line?

Quote:

$ splat --help *** ERROR: No transmitter site(s) specified! $ splat --==[ SPLAT! v1.3.0 Available Options... ]==-- -t txsite(s).qth (max of 4 with -c, max of 30 with -L) -r rxsite.qth -c plot coverage of TX(s) with an RX antenna at X feet/meters AGL -L plot path loss map of TX based on an RX at X feet/meters AGL -s filename(s) of city/site file(s) to import (5 max) -b filename(s) of cartographic boundary file(s) to import (5 max) -p filename of terrain profile graph to plot -e filename of terrain elevation graph to plot -h filename of terrain height graph to plot -H filename of normalized terrain height graph to plot -l filename of path loss graph to plot -o filename of topographic map to generate (.ppm) -u filename of user-defined terrain file to import -d sdf file directory path (overrides path in ~/.splat_path file) -m earth radius multiplier -n do not plot LOS paths in .ppm maps -N do not produce unnecessary site or obstruction reports -f frequency for Fresnel zone calculation (MHz) -R modify default range for -c or -L (miles/kilometers) -db threshold beyond which contours will not be displayed -nf do not plot Fresnel zones in height plots -fz Fresnel zone clearance percentage (default = 60) -gc ground clutter height (feet/meters) -ngs display greyscale topography as white in .ppm files -erp override ERP in .lrp file (Watts) -ano name of alphanumeric output file -ani name of alphanumeric input file -udt name of user defined terrain input file -kml generate Google Earth (.kml) compatible output -geo generate an Xastir .geo georeference file (with .ppm output) -dbm plot signal power level contours rather than field strength -gpsav preserve gnuplot temporary working files after SPLAT! execution -metric employ metric rather than imperial units for all user I/O If that flew by too fast, consider piping the output through 'less': splat | less Type 'man splat', or see the documentation for more details. This compilation of SPLAT! supports analysis over a region of 8 square degrees of terrain.

SPLAT! isn't a photoshop hack, but you can use gimp (or I suppose
photoshop) to hack with the png files it creates. I take the png files
and chop them up so they are acceptable to google earth, then make an
overlay out of them. Splat can do it, but unless things have changed, it
makes a kml file that can be too large for GE to accept. GE wants tiled
imagery. I haven't run it in maybe 18 months, so I can't really say much
without setting it up again.

I saw a GPS mentioned. I never found GPS elevation to be too accurate. I
have a barometer in my GPS. I never used it, so I can't vouch for it's
accuracy. But you can enter in the pressure from the airport, or
calibrate it to a known reference (known altitude for a position).

One idea would be to check the USGS monuments and find the closest
reference.
http://www.ngs.noaa.gov/cgi-bin/datasheet.prl

Note that sometimes these markers are on private property. Other times
they are in the middle of the street! it pays to look at the reference
on google earth before trying to use it. My Garmin gps60cs was good to
4ft, basically one lsb.

You could get a nearby reference, call the barometer, then quickly move
to your spot before the pressure changes. Or you might get lucky and
find there is a marker there already.

Topo maps have lines of constant altitude, usually on 20ft contours. You
could interpolate from the map.

If you really need accurate data, just pay for a survey. I would guess
something that simple is under a grand. I've paid for land surveys and
they are a few grand, but the altitude at one point is pretty simple.
Potentially the civil engineering firm might have topo data on file that
is not available to the general public. For instance, I paid for a
satellite topo to be done on some property. The civil engineering firm
has it on file and I'm sure it gets peeked at by other people.