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).

One can find references to changing/updating/hacking the firmware to remove limits here, and here, and as a product here.

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?

  • $\begingroup$ Just to clarify, are you saying that your application is specifically intended for balloons approaching or exceeding the Karman line and/or balloons used for cubesat testing? Otherwise, I'm having trouble seeing how this fits here rather than Aviation. $\endgroup$ – called2voyage Apr 7 '16 at 14:16
  • $\begingroup$ Cubesats are my target here @called2voyage . Balloons come into play in two ways. One might be wise to test a model cubesat or subsystem (communications, thermal, imaging, GPS, possibly sun or star finding) using a high altitude balloon flight first. This involves the altitude limit but not the velocity limit, which is the second issue - different GPS modules may use AND or OR on the criteria. $\endgroup$ – uhoh Apr 7 '16 at 15:47
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    $\begingroup$ Someone on the Raspberry Pi forums says: "Commercial GPS receivers conform to COCOM limit, (altitude < 18km) and (speed < 515m/sec) cannot be simultaneously exceeded, either can be exceeded, for prevention of use in missile or ICBM." They don't provide a reference though. $\endgroup$ – called2voyage Apr 7 '16 at 15:56
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    $\begingroup$ That discussion in the Raspberry Pi forums is actually quite helpful. It mentions the Adafruit Ultimate GPS which states the 515 m/s velocity limit. While the PDFs state 18,000 meter altitude limit, the VIDEO (found here) states 50 kilometers. This is consistent with the "newer" rules (see answer below). $\endgroup$ – uhoh Apr 8 '16 at 2:18
  • $\begingroup$ There is additional discussion in [community.balloonchallenge.org of GPS units which work at high-altitude, but at low speed. These are high altitude balloon applications. Also in this post in Ars Technica Openforum $\endgroup$ – uhoh Apr 10 '16 at 7:37

There is a standard clause included in all GPS receiver manuals regarding COCOM Limits. I cannot find the source of this clause, but since it is worded exactly the same in all the manuals I could find, I assumed it was probably derived directly from the regulation at some point:

COCOM Limits

The U.S. Department of Commerce requires that all exportable GPS products contain performance limitations so that they cannot be used in a manner that could threaten the security of the United States. The following limitations are implemented on the [named] receiver.

Immediate access to satellite measurements and navigation results is disabled when the receiver’s velocity is computed to be greater than 1000 knots, or its altitude is computed to be above 18,000 meters. The receiver continuously resets until the COCOM situation is cleared.

(emphasis mine)

It would seem based on this wording that the actual rule was OR.

However, this rule appears to no longer be enforced. I am not a lawyer, but it appears that the current rule for those states which accept the Missile Technology Control Regime's controls in its Technical Annex is as follows:

11.A.3. Receiving equipment for Global Navigation Satellite Systems (GNSS; e.g. GPS, GLONASS or Galileo), having any of the following characteristics, and specially designed components therefor:

a. Designed or modified for use in systems specified in 1.A.; or

b. Designed or modified for airborne applications and having any of the following:

  1. Capable of providing navigation information at speeds in excess of 600 m/s;

If your GPS reciever is capable of providing navigation information at speeds greater than 600 m/s, then you must have a special license, it would seem.

Bottom line:

If you wish to alter a GPS receiver to remove COCOM limits or purchase a special GPS receiver without COCOM limits, it would appear that this is acceptable, but there may be licensing that you have to apply for. I highly recommend consulting a lawyer before using such a GPS receiver in a COCOM situation.


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    $\begingroup$ OK got it. While almost everything seems to apply to systems with propulsion and/or controlled flight, 11.A.3.b suddenly pops up, now only a limit on air-speed velocity and not altitude. These are voluntary restrictions on export, but it's wise to learn more before doing anything. Thank you for "going deep" and putting this great answer together! $\endgroup$ – uhoh Apr 8 '16 at 1:55
  • $\begingroup$ Should we think of the actual CoCom restriction as "depreciated" and superseded by MTCR restrictions? While the term "CoCom restriction" is still used, CoCom itself ceased to function in 1994 and was superseded by the Wassenaar Arrangement where Section 7 covers a broad range of Avionics. Ouch! $\endgroup$ – uhoh Apr 8 '16 at 1:58
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    $\begingroup$ @uhoh I would think that yes, the MTCR restrictions superseded the CoCom restrictions, but I have not found that explicitly documented anywhere. $\endgroup$ – called2voyage Apr 9 '16 at 3:10
  • $\begingroup$ Oh, I didn't realize that I hadn't yet accepted the answer. Thanks again for your help - I appreciate you taking the time to write such a complete answer. $\endgroup$ – uhoh Apr 10 '16 at 7:16

EDIT: here is the most recent document as of Jan 2017: http://mtcr.info/wordpress/wp-content/uploads/2016/10/MTCR-TEM-Technical_Annex_2016-10-20.pdf If the link fails, then go here: http://mtcr.info/mtcr-annex/ and look for the most recent version.

The MTCR has recently been updated (OCT 2015). The new limit is 600 m/sec.



11.A.3. Receiving equipment GNSS e.g. GPS, GLONASS or Galileo
11.A.3. Receiving equipment for Global Navigation Satellite Systems (GNSS; e.g. GPS, GLONASS or Galileo), having any of the following characteristics, and specially designed components therefor:

a. Designed or modified for use in systems specified in 1.A.; or

b. Designed or modified for airborne applications and having any of the following:

  1. Capable of providing navigation information at speeds in excess of 600 m/s;
  2. Employing decryption, designed or modified for military or governmental services, to gain access to GNSS secure signal/data; or
  3. Being specially designed to employ anti-jam features (e.g. null steering antenna or electronically steerable antenna) to function in an environment of active or passive countermeasures.

Note: 11.A.3.b.2. and 11.A.3.b.3. do not control equipment designed for commercial, civil or 'Safety of Life' (e.g. data integrity, flight safety) GNSS services.

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    $\begingroup$ From 514 to 600 m/s. Only another 7100 m/s to go to reach LEO. Can you add a link to the most recent version? Since it appears I can buy cubesat GPS systems on the internet from several suppliers, how are they "getting around" these export controls? $\endgroup$ – uhoh Jun 17 '16 at 23:32
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    $\begingroup$ This was in my answer. I don't see what's new here. $\endgroup$ – called2voyage Jun 28 '16 at 20:35

I have just run across the following note in Section 05. Guidance, Navigation and Control of the NASA site [State of the Art of Small Spacecraft Technology]:

GPS units are controlled under the Export Administration Regulations (EAR) and must be licensed to remove COCOM limits${}^{15}$

${}^{15}$Office of the Federal Register, “FOREIGN AVAILABILITY DETERMINATION PROCEDURES AND CRITERIA,” vol. Title 15 Part 768.7, 2015.

I then found this at the Cornell Legal Access Institute:

§ 768.2 Foreign availability described.

(a) Foreign availability. Foreign availability exists when the Secretary determines that an item is comparable in quality to an item subject to U.S. national security export controls, and is available-in-fact to a country, from a non-U.S. source, in sufficient quantities to render the U.S. export control of that item or the denial of a license ineffective. For a controlled country, such control or denial is “ineffective” when maintaining such control or denying a specific license would not restrict the availability of items that would make a significant contribution to the military potential of the controlled country or combination of countries detrimental to the national security of the United States (see sections 5(a) and 3(2)(A) of the EAA.)

(b) Types of foreign availability. There are two types of foreign availability:

  • List item (1) Foreign availability to a controlled country; and

  • (2) Foreign availability to a non-controlled country.

Note to paragraph (B) of this section:

See §768.7 of this part for delineation of the foreign availability assessment procedures, and § 768.6 of this part for the criteria used in determining foreign availability.

§768.7 is quite long, and details a specific set of procedures for the determination of Foreign Availability. From what I understand, this is essentially saying if it is determined that the item or technology is already readily available for purchase outside the US, then one can apply for permission to export it from the US.

This applies to exporting from the US. So far I haven't found any rules against building a LEO-capable GPS unit in the US for ones own cubesat to be launched within the US or by a US launch provider, nor selling one to someone else within the US. (I've chosen the US as an example of a "CoCom country" here.)


The COCOM limit is a ITU requirement, it is Global and it has to do with import/export. If your device comes without COCOM limits, it is considered "Dual Use" by the Dept. of State and must be licensed by them for Export (Same with just about every country in the world.) With COCOM limits, you can export with permission of the Dept. of Commerce. If you make it and don't export it you're OK. If you buy it in the USA and don't export it, you are OK. If you sell one without COCOM limits, you must follow the ITAR rules and regulations or you go to jail. Most small cheap units seem to have COCOM limits "Hard Wired" and can't be "removed".

  • $\begingroup$ Rather than make a second answer, you should edit this information into your original answer using the 'edit' link that appears below the answer. $\endgroup$ – Jerard Puckett Sep 7 '16 at 0:25

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