<< I am under the impression that a GPS cannot give a reliable speed
determination under 15 mph? >>
Sometimes true, sometimes not. When the GPSIII gets into "3D mode" (position
+altitude), it is extremely accurate. (except altitude, which seems to have a
300ft tolerance no matter what!)
When I walk with it in my hand, it almost always reads 3 or so mph with
acurate compass. When I stop it reads 0.0mph. Sometimes it will fluctuate
around 1mph. In my vehicle, I compare it at 20mph against the police radar
leaving the gate of US Navy Submarine Base Bangor, WA it always reads
identical..
There are many factors that affect GPS. S/A being the most influential of
course. No matter how much we may hate the government influencing 'our toys',
we are still tapping into 'their system'. (We just paid for it) The same
system that guided 75 of our missiles a month or so ago within feet of their
targets. And the same system that may be 'shut off', or deliver misleading
information to keep 'non-friendly birdies' from coming within feet of our
backyards using our system against us.
As everyone else who has put a large sum of money into their gps toys, I would
like mine to be as accurate as it possibly can. BUT, I still wouldn't solely
rely on it. GPS is a good ocean navigation tool. If you can't see any land,
it will give your approximate position. If you can see land, you are better
off taking a visual fix, and plotting on a NOAA chart. The same way every US
Navy ship (surface and sub) is still required to do. GPS (military grade) and
LORAN are only a reference for them.
GPS is more accurate than what most will give credit. I have a waypoint
programmed for my driveway. When I drive to work, to the mall, to the boat
ramp, etc then come home.... I am always within 10 feet of my exact lat and
long........ toys toys toys........
Russ de Ment
borrowed grandpas P-19
Silverdale, WA