4 ms·

America's 'Gold Standard' GPS Risks Falling Behind Rival Systems

25 points by julienchastang 3y ago

morninglight 3y ago
This is what we are using - https://www.sparkfun.com/products/23088 https://www.sparkfun.com/products/23088 ..
- ddejohn 3y ago
  > The mosaic-X5 module is an ultra-low power, multi-band, multi-constellation GNSS receiver capable of delivering centimeter-level precision at high update rates. Dang. I was under the impression that GPS receivers this precise were available to the public. I participated in a rocketry project in 2015 and that's what we were told anyway.
  - defrost 3y ago
    They've been available "to the public" (ie. non military) for 30 odd years .. it's just the components have been expensive and have required "some technical expertise" to glue it all together. The cm-level accuracy here is achieved by having two recievers, one fixed, one roving - with the fixed one acting as a base station that continuously broadcasts the "drift" in its fixed position as reported by the satellites - that's the error signal - deduct that and you've got improved position. We did this as part of geophysical surveying from aircraft and other moving platforms in the early 90s - recording the base station signal and merging that with other postfix error correction procedures in post processing. The military had that for mobile battlefield units to improve accuracy, fixed ground base stations broadcasting fixes to missiles. No real time updates in geophysics as the first priority was to minimise magnetic, electromagnetic, radiometric, gravitational, etc "noise" as much as possible - keep generation sources to a minimum and shield them as much as possible within the craft.
    - dilyevsky 3y ago
      > They've been available "to the public" (ie. non military) for 30 odd years .. it's just the components have been expensive and have required "some technical expertise" to glue it all together. That is not what gps.gov says - only since 2014 https://www.gps.gov/systems/gps/modernization/civilsignals/#L2C https://www.gps.gov/systems/gps/modernization/civilsignals/#...
      - defrost 3y ago
        This: https://learn.sparkfun.com/tutorials/what-is-gps-rtk https://learn.sparkfun.com/tutorials/what-is-gps-rtk base + roving receiver pairs, has always been an option for 30 odd years - it's what gives the increased accuracy. L2C achieves ionospheric (and other) correction by another "dual" approach - dual frequencies, this has only recently been available. All the same, as I stated, non US military, non US companies have been using twin receivers to improve US GPS accuracy for 30 odd years. It was used here: https://www.mrd.gov.fj/index.php/31-products/58-regional-airborne-magnetic-and-radiometric-data https://www.mrd.gov.fj/index.php/31-products/58-regional-air... for example, 26 years ago.
    - tivert 3y ago
      > The cm-level accuracy here is achieved by having two recievers, one fixed, one roving - with the fixed one acting as a base station that continuously broadcasts the "drift" in its fixed position as reported by the satellites - that's the error signal - deduct that and you've got improved position. https://en.wikipedia.org/wiki/Differential_GPS https://en.wikipedia.org/wiki/Differential_GPS > The military had that for mobile battlefield units to improve accuracy, fixed ground base stations broadcasting fixes to missiles. Do you have a source for that? Because it doesn't make any sense to me. The enemy is unlikely to be willing to site a DGPS base station nearby to increase the accuracy of missiles being used to attack it. My understanding is the military has always had access to multiple GPS frequencies, which allow it to significantly reduce certain sources of error that single-frequency civilian units are subject to.
      - defrost 3y ago
  - dilyevsky 3y ago
    In 2014 they started broadcasting L2C signal which improved civilian precision to basically military level[0] There is also preproduction L5 now which gives you cm level precision [0] - https://www.gps.gov/systems/gps/modernization/civilsignals/#L2C https://www.gps.gov/systems/gps/modernization/civilsignals/#...
    - londons_explore 3y ago
      Notable that the military encrypted code was also usable by civilians if you were happy to do 'codeless decoding'. Basically, you might not be able to decrypt the signal but it still contains useful timing information.
  - vikramkr 3y ago
    Is this one that you quoted not available? That looks like a link to buy that recieiver in the parent comment, don't see anything about needing to be military or something else that would block it from being used for civilian use?
  - ddejohn 3y ago
    weren't*
- cvccvroomvroom 3y ago
  Looks alright. Multi GNSS that's well-engineered can be far more effective than using one system. The trick will be assuring the same geo model and accounting for the differences in calibrated time. Pseudo-wavelength counting is essential but also it requires that the satellites good, relativistically-corrected time sources by time-of-flight visual confirmation calibration of position and velocity. [pdf] https://www.opsjournal.org/DocumentLibrary/Uploads/Mudrak_article_final.pdf https://www.opsjournal.org/DocumentLibrary/Uploads/Mudrak_ar...
mike_d 3y ago
https://archive.ph/MxmE7 https://archive.ph/MxmE7
cvccvroomvroom 3y ago
Lol. Okay. This article is shit and wrong. GPS has had readily achieved kinematic (while moving) accuracy 10 mm horizontally and 1000 mm vertically since 2000 with a base station or good WAAS, and good constellation coverage (flat land), even before Clinton turned off SA (because base stations defeated it). Cell phones use tower+GNSS triangulation, so accuracy and precision varies with tower coverage and satellite positions of the constellations. In the 2000's, farm and industrial equipment could accurately calculate machine angle using 2 GPS antennas. It's only improved since then as things changed. Besides numeric peeing contests, there is nothing substantive in this article, just vague, ignorant, rhetorical FUD.
Rebelgecko 3y ago
Article doesn't make sense to me. It spends time on silly stats like # of total sats per GNSS constellation, without saying why we should care. They complain that even with the new signals, GPS still transmits on the same OG frequency it always has, but doesn't say why that's bad (it can't be that bad of a frequency since Galileo chose to use the same one) IMO GPS is the gold standard because it's reliable. There's been accuracy issues and other glitches, but I don't think there's been any global outages in the last 50 years. Hell, just having no outages in the last decade already puts it ahead of Galileo and GLONASS.

morninglight 3y ago

This is what we are using - https://www.sparkfun.com/products/23088 https://www.sparkfun.com/products/23088 ..

ddejohn 3y ago
> The mosaic-X5 module is an ultra-low power, multi-band, multi-constellation GNSS receiver capable of delivering centimeter-level precision at high update rates. Dang. I was under the impression that GPS receivers this precise were available to the public. I participated in a rocketry project in 2015 and that's what we were told anyway.
- defrost 3y ago
  They've been available "to the public" (ie. non military) for 30 odd years .. it's just the components have been expensive and have required "some technical expertise" to glue it all together. The cm-level accuracy here is achieved by having two recievers, one fixed, one roving - with the fixed one acting as a base station that continuously broadcasts the "drift" in its fixed position as reported by the satellites - that's the error signal - deduct that and you've got improved position. We did this as part of geophysical surveying from aircraft and other moving platforms in the early 90s - recording the base station signal and merging that with other postfix error correction procedures in post processing. The military had that for mobile battlefield units to improve accuracy, fixed ground base stations broadcasting fixes to missiles. No real time updates in geophysics as the first priority was to minimise magnetic, electromagnetic, radiometric, gravitational, etc "noise" as much as possible - keep generation sources to a minimum and shield them as much as possible within the craft.
  - dilyevsky 3y ago
    > They've been available "to the public" (ie. non military) for 30 odd years .. it's just the components have been expensive and have required "some technical expertise" to glue it all together. That is not what gps.gov says - only since 2014 https://www.gps.gov/systems/gps/modernization/civilsignals/#L2C https://www.gps.gov/systems/gps/modernization/civilsignals/#...
    - defrost 3y ago
      This: https://learn.sparkfun.com/tutorials/what-is-gps-rtk https://learn.sparkfun.com/tutorials/what-is-gps-rtk base + roving receiver pairs, has always been an option for 30 odd years - it's what gives the increased accuracy. L2C achieves ionospheric (and other) correction by another "dual" approach - dual frequencies, this has only recently been available. All the same, as I stated, non US military, non US companies have been using twin receivers to improve US GPS accuracy for 30 odd years. It was used here: https://www.mrd.gov.fj/index.php/31-products/58-regional-airborne-magnetic-and-radiometric-data https://www.mrd.gov.fj/index.php/31-products/58-regional-air... for example, 26 years ago.
  - tivert 3y ago
    > The cm-level accuracy here is achieved by having two recievers, one fixed, one roving - with the fixed one acting as a base station that continuously broadcasts the "drift" in its fixed position as reported by the satellites - that's the error signal - deduct that and you've got improved position. https://en.wikipedia.org/wiki/Differential_GPS https://en.wikipedia.org/wiki/Differential_GPS > The military had that for mobile battlefield units to improve accuracy, fixed ground base stations broadcasting fixes to missiles. Do you have a source for that? Because it doesn't make any sense to me. The enemy is unlikely to be willing to site a DGPS base station nearby to increase the accuracy of missiles being used to attack it. My understanding is the military has always had access to multiple GPS frequencies, which allow it to significantly reduce certain sources of error that single-frequency civilian units are subject to.
    - defrost 3y ago
- dilyevsky 3y ago
  In 2014 they started broadcasting L2C signal which improved civilian precision to basically military level[0] There is also preproduction L5 now which gives you cm level precision [0] - https://www.gps.gov/systems/gps/modernization/civilsignals/#L2C https://www.gps.gov/systems/gps/modernization/civilsignals/#...
  - londons_explore 3y ago
    Notable that the military encrypted code was also usable by civilians if you were happy to do 'codeless decoding'. Basically, you might not be able to decrypt the signal but it still contains useful timing information.
- vikramkr 3y ago
  Is this one that you quoted not available? That looks like a link to buy that recieiver in the parent comment, don't see anything about needing to be military or something else that would block it from being used for civilian use?
- ddejohn 3y ago
  weren't*
cvccvroomvroom 3y ago
Looks alright. Multi GNSS that's well-engineered can be far more effective than using one system. The trick will be assuring the same geo model and accounting for the differences in calibrated time. Pseudo-wavelength counting is essential but also it requires that the satellites good, relativistically-corrected time sources by time-of-flight visual confirmation calibration of position and velocity. [pdf] https://www.opsjournal.org/DocumentLibrary/Uploads/Mudrak_article_final.pdf https://www.opsjournal.org/DocumentLibrary/Uploads/Mudrak_ar...

mike_d 3y ago

https://archive.ph/MxmE7 https://archive.ph/MxmE7

cvccvroomvroom 3y ago

Lol. Okay. This article is shit and wrong. GPS has had readily achieved kinematic (while moving) accuracy 10 mm horizontally and 1000 mm vertically since 2000 with a base station or good WAAS, and good constellation coverage (flat land), even before Clinton turned off SA (because base stations defeated it). Cell phones use tower+GNSS triangulation, so accuracy and precision varies with tower coverage and satellite positions of the constellations. In the 2000's, farm and industrial equipment could accurately calculate machine angle using 2 GPS antennas. It's only improved since then as things changed. Besides numeric peeing contests, there is nothing substantive in this article, just vague, ignorant, rhetorical FUD.

Rebelgecko 3y ago

Article doesn't make sense to me. It spends time on silly stats like # of total sats per GNSS constellation, without saying why we should care. They complain that even with the new signals, GPS still transmits on the same OG frequency it always has, but doesn't say why that's bad (it can't be that bad of a frequency since Galileo chose to use the same one) IMO GPS is the gold standard because it's reliable. There's been accuracy issues and other glitches, but I don't think there's been any global outages in the last 50 years. Hell, just having no outages in the last decade already puts it ahead of Galileo and GLONASS.