[Proj] Scale factor for Transverse Mercator

Clifford J Mugnier cjmce at lsu.edu
Wed Sep 10 18:42:33 EDT 2008

Originally, the military did not expect Academics to figure out a way to get around the single point-positioning mode of the NAVSTAR (GPS) system.  The DoD figured that on paper, dithering the signal would not allow our combatants to utilize our GPS system as guidance for their ordnance against us.
It was expected that dithering the signal would/could increase the "circle of uncertainty" to 100-300 meters, thus rendering GPS unusable to our enemies in a conventional, non-nuclear-warhead war.  Remember, NAVSTAR was originally conceived in the early 1970s, and was not envisioned as ever being useable for the civilian community - at that time.

Remember it was Niels Bohr that said, "Prediction is a pretty tough thing to do, especially in the future."

Cliff Mugnier


From: proj-bounces at lists.maptools.org on behalf of Gerald I. Evenden
Sent: Wed 10-Sep-08 14:37
To: PROJ.4 and general Projections Discussions
Subject: Re: [Proj] Scale factor for Transverse Mercator

On Wednesday 10 September 2008 3:17:50 pm Clifford J Mugnier wrote:
> The State Plane Coordinate Systems were
> The Scale Factor at a Point maximum of
> 1:2,500 at the Central Meridian was considered OK for Fire Control because
> for this application, the 6° Zones were limited in longitudinal extent
> because of the convergence angle between Grid North and Geodetic North -
> soldiers don't really care that much about the difference between Grid
> Distance and Geodetic Distance ... the blast radius of a 155mm Howitzer
> shell takes care of that little "problem."

Under the same logic, I could never understand the reason for fuzzing the GPS
signals because what difference does a few meters mean with the blast radius
of an H-bomb?

The wonders of the military mind.

If one is laying in air burst of with 155 a little fuzz will not make much
difference because you are probably doing a carpet barrage anyway.  But if
you are trying to knock out just one house in a city block (like they do with
the smart bombs) then ... .  Curious about the electronics in some of the
newer artillery pieces.  New command and control is something else from what
little I've seen and heard.

The whole religious complexion of the modern world is due
to the absence from Jerusalem of a lunatic asylum.
-- Havelock Ellis (1859-1939) British psychologist

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