Re: Consequences of inadequate docs/training?

Subject: Re: Consequences of inadequate docs/training?
From: eric -dot- dunn -at- ca -dot- transport -dot- bombardier -dot- com
To: "TECHWR-L" <techwr-l -at- lists -dot- raycomm -dot- com>
Date: Thu, 28 Mar 2002 10:12:47 -0500

>>GPS signals are deliberatlly degraded for civilian use. Military GPS devices
>>can be accurate to within a handful of meters. Civilian GPS devices are
>>accurate to anywhere from 50 to 150 meters. This was done to prevent hostile
>>forces from using GPS to guide bombs to their targets.

While this is going off-topic a bit for the list, thought we should at least get
the technical issues correct. (Don't many argue that technology is more
important than writing?)

The difference in civilian GPS and military GPS was true but it has changed. The
civilian GPS channels are no longer scrambled (actually, a random error was
deliberately induced). There was a big to-do with Bill Clinton throwing the
switch if I remember correctly. Maybe it was just as he signed the bill. Just be
prepared that if any threat is detected that all civilian GPS suddenly stops

An interesting side note is that the military GPS was never the most accurate
system. As the military would not give access to the more accurate readings, the
coast guard developed their own system as the civilian GPS was too imprecise for
their needs. Their solution was to use GPS to locate a location for which they
new the exact coordinates. They could then instantly calculate and broadcast the
GPS 'error'.

Coast guard GPS users were then provided with GPS receivers linked with radio
receivers. The combination of GPS location and radio received error then gave
them a reading that (at least from what I can remember) was better than the
military equipment.

Eric L. Dunn

PS: As much of this is from hazy memory I'd welcome any corrections or
directions to sources of fact.

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