I wanted to ask this at aviation SE because they are quite rules-and-regulations oriented there, but this question is not (really) about aviation.
I'm trying to understand the current situation for obtaining, and using GPS receivers that continue to work at very high altitude, or high speed, or both. Due to the existence of CoCom reguations I believe all GPS module manufacturers added limits to their products - probably in firmware - so that they would stop working if some combination of two limits had been reached. The limits are (I believe)
altitude > 18km and
speed > 1000 knots (about 0.5 kilometer per second). I think, although I am not sure, that these were implemented across the board by all manufacturers to avoid any possibility of sanctions or falllout similar to the CNC machines sold and potential use for quiet sub propellors and subsequent sanctions.
One subtlety is the question if the two limits (altitude, speed) are applied in an OR or AND configuration, which matters if your application is balloon borne or even testing cubesat subsystems via balloon.
This paragraph in Wired is intriguing, but it doesn't actually tell what the "more relaxed rules" are!
"Due to more relaxed rules, we now have the possibility to use GPS signals at higher altitudes and speeds. The problem is people normally don’t know how to either construct their own receivers or disable/modify the limits inside ready available modules (until now).
My Question is: What exactly are the rules now? Is it "OK" to change firmware or otherwise remove limits on ones own module? Can manufacturers of GPS modules ship them without the limits in certain cases? What are the conditions? Where are the rules written so we can read them?