6 ms·

I would be bit careful. GPS is military technology and commercial versions must have limitations, to be non-usable in rockets (max speed, max altitude...).

by jkot 12y ago

tyho 12y ago
Says the USA, thankfully the author is not based there. That being said, the USA does seem to think many of its laws apply all over the globe.
- ape4 12y ago
  He might want to visit the USA some time.
- ceequof 12y ago
  Incorrect. The relevant agreement is the Missile Technology Control Regime, an informal partnership between 34 countries. http://en.wikipedia.org/wiki/Missile_Technology_Control_Regime http://en.wikipedia.org/wiki/Missile_Technology_Control_Regi... Unlocked GPS receivers are classified as dual-use missile-related components under category II, item 11, section A.3: http://www.mtcr.info/english/MTCR-April2011-Technical-Annex.pdf http://www.mtcr.info/english/MTCR-April2011-Technical-Annex.... 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.
  - tyho 12y ago
    Huh, I should have checked that first. How well do you think you could argue that since the treaty did not specify what reference frame you were supposed to use to calculate the 600 m/s limit, you decided to use the reference frame of the receiver and therefore no limit is required because the speed is always 0? I would have thought GPS people most of all would have understood this problem \s.
    - ceequof 12y ago
      My crystal ball tells me that the judge would find your argument very amusing, but not substantive.
  - jevinskie 12y ago
    Unfortunately many receivers have a (speed > X || altitude > Y) check when, IIRC, the law only requires (I don't see the altitude part in your quote) (speed > X && altitude > Y). I think the altitude limit was 20 km or 25 km. Anyways, it is a pain for people who want to put a receiver on a high altitude balloon. I was able to... find... a modified firmware for my SIRF receiver but I have been to afraid to flash it. Besides, I don't even know if the receiver has the "bad" logic. I've been jonesing to make a SDR GPS simulator that generates a signal that I can feed directly into the antenna port on the receiver to test high altitude functionality.
    - ceequof 12y ago
      MTCR is an informal agreement, not a treaty. Its provisions are actually implemented by laws in the member nations-- in the US, that's the International Traffic In Arms Regulations Act. (ITAR) ITAR Category XV, Section c: Global Positioning System (GPS) receiving equipment specifically designed, modified or configured for military use; or GPS receiving equipment with any of the following characteristics: 1. Designed for encryption or decryption (e.g., Y-Code) of GPS precise positioning service (PPS) signals; 2. Designed for producing navigation results above 60,000 feet altitude and at 1,000 knots velocity or greater; So the US limit isn't even in metric units! Consulting my psychic powers, since I haven't bothered to dig up the laws for each member nation, I predict that each nation implements MTCR slightly differently, some using the word AND, some using the word OR. Since a GPS manufacturer wants to sell worldwide, they would have to use the strictest limits possible.
kiiski 12y ago
Aren't those limitations just in the USA? I'd guess that someone in .co.uk should be able to do what ever they want, especially as a non-commercial project.
- toomuchtodo 12y ago
  Yes, but if you violate ITAR, you'd probably want to avoid transiting the US in the future. We're pretty militant about enforcing our laws beyond what you'd consider sovereign boundaries.
chisleu 12y ago
Came for this. This allows someone to build GPS-guided missiles, artillery, etc. The laws need to be changed, because consumer-programmable things like FPGAs and SBCs like BBB/RPi have made weaponizing with even commercially-available, off-the-shelf products super easy. For instance, building gps-powered drones with thermite self destruct and an explosive/incendiary payload is fairly straight forward and extremely dangerous with little ability to investigate the violator. ICBMs and fast-flying missiles are much harder.
- toomuchtodo 12y ago
  Don't even need FPGAs; you could do it all in software and use very light software defined radio hardware.
  - chisleu 12y ago
    You need to poll many frequencies at once, very quickly, in order to make a missile that can respond fast enough. Maybe it's possible with a very wide SDR, but I've not seen one where it was.
    - cnvogel 12y ago
      http://www.gnss-sdr.org/ http://www.gnss-sdr.org/ claims to be able to work with RTLSDR dongles (cost ~$10 and provides 3,2 MHz Bandwidth. Original article's "homemade GPS" has 2,5 MHz BW). Also: http://www.rtl-sdr.com/tag/gps/ http://www.rtl-sdr.com/tag/gps/
      - chisleu 12y ago
        Doing it, and doing it fast enough to guide a missile at > mach 2 are different things entirely. The rate that you have to constantly be calculating the spin (if any) and the vector and speed is incredible. OTS 5-10hz refresh will not cut it. That said OTC stuff is so dangerous now that I think we should roll back the laws to allow home lab/hackerspace science to evolve. I would love to launch a rocket from weather balloons, but it would stand little chance of getting anywhere with OTS GPS gear.
cnvogel 12y ago
If 1000 lines of Verilog code (or a little bit of patching in a commercial receiver's firmware, for that matter) is the only thing missing from the terrorists having a working cruise missile, then we're screwed anyway... Personally I'd love to see more of the advanced features (such as carrier phase measurements and also multiple antenna support) being available in affordable hardware. Preferably in an open system, being open source, providing schematic diagrams, having open APIs and allow access to raw measurement data.
- krapht 12y ago
  Ublox LEA-6T + RTKLIB not enough?
  - jhayward 12y ago
    RTKLIB doesn't do well with 'challenging' environments like tree canopy induced non-LOS multipath, etc. It would be nice to have access to some deeper internals (doppler bucket size, carrier phase PLL info, etc) to be able to separate outlier per-satellite epochs from good ones.
mcculley 12y ago
Selective Availability was turned off in 2000 (15 years ago today) after the US government demonstrated that they could limit accuracy over any region they chose if they ever need to[1]. Most GPS receivers now implement crippled behavior at certain altitudes and speeds, but nobody assumes this to be a dependable defense. 1: "Additionally, we have demonstrated the capability to selectively deny GPS signals on a regional basis when our national security is threatened." from http://www.faa.gov/about/office_org/headquarters_offices/ato/service_units/techops/navservices/gnss/gps/policy/presidential/ http://www.faa.gov/about/office_org/headquarters_offices/ato...
- spitfire 12y ago
  There's more than just SA at work here. There's still speed and altitude limits in force via ITAR (arms trafficking regulations) that GPS manufacturers are not allowed to report GPS data. I think it something like 512 m/s and 18000M.

I would be bit careful. GPS is military technology and commercial versions must have limitations, to be non-usable in rockets (max speed, max altitude...).

by jkot 12y ago

I would be bit careful. GPS is military technology and commercial versions must have limitations, to be non-usable in rockets (max speed, max altitude...).

tyho 12y ago

Says the USA, thankfully the author is not based there. That being said, the USA does seem to think many of its laws apply all over the globe.

ape4 12y ago
He might want to visit the USA some time.
ceequof 12y ago
Incorrect. The relevant agreement is the Missile Technology Control Regime, an informal partnership between 34 countries. http://en.wikipedia.org/wiki/Missile_Technology_Control_Regime http://en.wikipedia.org/wiki/Missile_Technology_Control_Regi... Unlocked GPS receivers are classified as dual-use missile-related components under category II, item 11, section A.3: http://www.mtcr.info/english/MTCR-April2011-Technical-Annex.pdf http://www.mtcr.info/english/MTCR-April2011-Technical-Annex.... 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.
- tyho 12y ago
  Huh, I should have checked that first. How well do you think you could argue that since the treaty did not specify what reference frame you were supposed to use to calculate the 600 m/s limit, you decided to use the reference frame of the receiver and therefore no limit is required because the speed is always 0? I would have thought GPS people most of all would have understood this problem \s.
  - ceequof 12y ago
    My crystal ball tells me that the judge would find your argument very amusing, but not substantive.
- jevinskie 12y ago
  Unfortunately many receivers have a (speed > X || altitude > Y) check when, IIRC, the law only requires (I don't see the altitude part in your quote) (speed > X && altitude > Y). I think the altitude limit was 20 km or 25 km. Anyways, it is a pain for people who want to put a receiver on a high altitude balloon. I was able to... find... a modified firmware for my SIRF receiver but I have been to afraid to flash it. Besides, I don't even know if the receiver has the "bad" logic. I've been jonesing to make a SDR GPS simulator that generates a signal that I can feed directly into the antenna port on the receiver to test high altitude functionality.
  - ceequof 12y ago
    MTCR is an informal agreement, not a treaty. Its provisions are actually implemented by laws in the member nations-- in the US, that's the International Traffic In Arms Regulations Act. (ITAR) ITAR Category XV, Section c: Global Positioning System (GPS) receiving equipment specifically designed, modified or configured for military use; or GPS receiving equipment with any of the following characteristics: 1. Designed for encryption or decryption (e.g., Y-Code) of GPS precise positioning service (PPS) signals; 2. Designed for producing navigation results above 60,000 feet altitude and at 1,000 knots velocity or greater; So the US limit isn't even in metric units! Consulting my psychic powers, since I haven't bothered to dig up the laws for each member nation, I predict that each nation implements MTCR slightly differently, some using the word AND, some using the word OR. Since a GPS manufacturer wants to sell worldwide, they would have to use the strictest limits possible.

kiiski 12y ago

Aren't those limitations just in the USA? I'd guess that someone in .co.uk should be able to do what ever they want, especially as a non-commercial project.

toomuchtodo 12y ago
Yes, but if you violate ITAR, you'd probably want to avoid transiting the US in the future. We're pretty militant about enforcing our laws beyond what you'd consider sovereign boundaries.

chisleu 12y ago

Came for this. This allows someone to build GPS-guided missiles, artillery, etc. The laws need to be changed, because consumer-programmable things like FPGAs and SBCs like BBB/RPi have made weaponizing with even commercially-available, off-the-shelf products super easy. For instance, building gps-powered drones with thermite self destruct and an explosive/incendiary payload is fairly straight forward and extremely dangerous with little ability to investigate the violator. ICBMs and fast-flying missiles are much harder.

toomuchtodo 12y ago
Don't even need FPGAs; you could do it all in software and use very light software defined radio hardware.
- chisleu 12y ago
  You need to poll many frequencies at once, very quickly, in order to make a missile that can respond fast enough. Maybe it's possible with a very wide SDR, but I've not seen one where it was.
  - cnvogel 12y ago
    http://www.gnss-sdr.org/ http://www.gnss-sdr.org/ claims to be able to work with RTLSDR dongles (cost ~$10 and provides 3,2 MHz Bandwidth. Original article's "homemade GPS" has 2,5 MHz BW). Also: http://www.rtl-sdr.com/tag/gps/ http://www.rtl-sdr.com/tag/gps/
    - chisleu 12y ago
      Doing it, and doing it fast enough to guide a missile at > mach 2 are different things entirely. The rate that you have to constantly be calculating the spin (if any) and the vector and speed is incredible. OTS 5-10hz refresh will not cut it. That said OTC stuff is so dangerous now that I think we should roll back the laws to allow home lab/hackerspace science to evolve. I would love to launch a rocket from weather balloons, but it would stand little chance of getting anywhere with OTS GPS gear.

cnvogel 12y ago

If 1000 lines of Verilog code (or a little bit of patching in a commercial receiver's firmware, for that matter) is the only thing missing from the terrorists having a working cruise missile, then we're screwed anyway... Personally I'd love to see more of the advanced features (such as carrier phase measurements and also multiple antenna support) being available in affordable hardware. Preferably in an open system, being open source, providing schematic diagrams, having open APIs and allow access to raw measurement data.

krapht 12y ago
Ublox LEA-6T + RTKLIB not enough?
- jhayward 12y ago
  RTKLIB doesn't do well with 'challenging' environments like tree canopy induced non-LOS multipath, etc. It would be nice to have access to some deeper internals (doppler bucket size, carrier phase PLL info, etc) to be able to separate outlier per-satellite epochs from good ones.

mcculley 12y ago

Selective Availability was turned off in 2000 (15 years ago today) after the US government demonstrated that they could limit accuracy over any region they chose if they ever need to[1]. Most GPS receivers now implement crippled behavior at certain altitudes and speeds, but nobody assumes this to be a dependable defense. 1: "Additionally, we have demonstrated the capability to selectively deny GPS signals on a regional basis when our national security is threatened." from http://www.faa.gov/about/office_org/headquarters_offices/ato/service_units/techops/navservices/gnss/gps/policy/presidential/ http://www.faa.gov/about/office_org/headquarters_offices/ato...

spitfire 12y ago
There's more than just SA at work here. There's still speed and altitude limits in force via ITAR (arms trafficking regulations) that GPS manufacturers are not allowed to report GPS data. I think it something like 512 m/s and 18000M.