The following statement was in an earlier post:
"I have found that the software can be off as little as 10 feet, and as =
much as 1,000 feet."

The network of nearly 30 satellites for global positioning coordinates was
developed, launched and is controlled by the Defense Dept for military use.

The "error" factor in GPS accuracy is controlled by the US Defense
Department. It's not within a particular units software.

It is called "selective availability", which, in a nutshell means: when the
D.O.D. has the error factor "turned on", your readings, depending on which
satellites you're locked on, will give you a position OFF by several meters
to close to a kilometer. This is to make "enemies" equipment less accurate
for their targeting purposes. "Accurate" postions of one meter
are "available selectively" via the D.O.D.'s big hand on the switch.

Of course, if a nuke hits 1000 meters away from the desired target....does
it really matter? There's the rub and the controversy.

The D.O.D.'s turning off and on the "SA" over the years has been a point of
contention for GPS manufacturers and industries that use GPS heavily....ie:
shipping and maritime companies, as well as a robust pleasure boating
industry. Those users should realize the system was NOT developed for their
use. It was developed for accurate targeting and guidance purposes
on "smart" bombs.
The D.O.D. has said that eventually the SA will be eliminated.

To overcome the error in maritime navigation via GPS, units with "D-GPS"
capability have been popular for about 10 years. The "D-GPS" units
(Differential GPS) use LORAN land based transmitters to fall back on when
SA is causing error. The LORAN system uses triangulation between
transmitter signals and calculates signal delay between the signals at the
LORAN receiver to determine postion. It is VERY accurate, but will be
phased out completely soon.
LORAN is controlled by the Coast Guard.

Now that y'all are in a coma from my boring discertation, I'll be quiet now.

Regards,
Paul W. Moring
Va to SC to IN

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