HP 29 GPS: the view from 9865 meters!

[StephenG1CMZ]

(06-02-2017 06:01 AM)PANAMATIK Wrote:  

(06-01-2017 10:40 PM)Paul Dale Wrote:  Military grade GPS units will. Civilian ones are artificially limited to a maximum altitude of 18 km and a maximum speed of 1,000 knots (sometimes both, sometimes either).

These limits are imposed by software, so it is possible to remove them from some GPS devices by updating their firmware.

Pauli

That's interesting. I knew only of the software imposed position inaccuracy, which is deactivated for civilian areas today, but of course from military view height and speed would be important informations for enemy missiles. From mathematical view GPS could provide altitudes high above (on the other side of) the GPS satellites up to many thousands of kilometers to get positions relative to earth, until distances are too far to get high angles between them. But I assume no GPS satellite will direct its signals away from earth, it would be a waste of transmission power.

I don't know what happens in the HP-29E GPS when more than 1000 knots are displayed (see picture no digit left), Geoff, please keep below this barrier.

Bernhard

I'm thinking the primary reason for the speed/altitude limits is not because of reporting where an aircraft is as a potential target for a missile...
It's to try to prevent a commercial GPS being utilised as a guidance system in an improvised missile.
But it has been a while...