Take the 2-minute tour ×
Geographic Information Systems Stack Exchange is a question and answer site for cartographers, geographers and GIS professionals. It's 100% free, no registration required.

I am looking for a GPS module that I can use in a high-altitude project. The problem I have discovered is that GPS manufacturers are required to place a set of restrictions on GPS modules. The restrictions set a maximum speed and altitude at which the device should stop functioning. Basically, this limits someone's ability to build a cruise missile.

From what I understand, it is not illegal to have a GPS receiver without these limitations, it is illegal to export it from the U.S. without considering it a weapon.

If I am not mistaken, GPS is also used to track some satellites in orbit, so as long as the orbiting satellite is not in geo-synchronous orbit or further. Obviously, these GPS receivers do not have the limit, as both the height and velocity would far exceed the mandate.

Does anyone know of a GPS unit that does not have these limitations, or, is there a unit that allows you to flash the firmware and manually remove the limitations?

Link to mention of limitations: http://en.wikipedia.org/wiki/CoCom#Legacy

share|improve this question
1  
Interesting question - what 'high altitude project' would this be? Assuming not cruise missile ... balloon? Are the speed and altitude issues BOTH considerations for you? –  Simbamangu Feb 5 '12 at 7:33
1  
@Simbamangu No cruise missles, just a high-altitude balloon. But, I would like to find a receiver with none of the limitations, then I can go for a satellite launch...OSCAR, ftw! –  Jonathan Feb 5 '12 at 7:58
1  
If you have a follow the links at the bottom of the wikipedia page, one mentions a Trimble embedded GPS module that is known to work for balloons; the article suggests that trial-and-error is the only way to figure out what does and doesn't work! –  Simbamangu Feb 5 '12 at 12:15
add comment

2 Answers 2

Here's a page that discusses several models of GPS that are known to work in balloon applications: http://ukhas.org.uk/guides:gps_modules

It looks like the COCOM limits are imposed differently by manufacturers - some use an altitude 'OR' speed limit check, the others use 'AND'.

My next question would be just how much 3D accuracy you would get out of a GPS unit at 100,000 feet!

share|improve this answer
add comment

The US Government GPS Standard Positioning Service Performance Standard, appendix A, guarantees coverage up to an altitude of 3000km. Accuracy of a standard receiver would in no way be reduced at high altitude. High velocity is a bit different - the increase dopplar shift requires a receiver to search a large frequency range in order to lock on to the signal broadcast.

share|improve this answer
add comment

Your Answer

 
discard

By posting your answer, you agree to the privacy policy and terms of service.

Not the answer you're looking for? Browse other questions tagged or ask your own question.