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.
> 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.
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.
> 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.
> 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.
> 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.
It doesn't require the cooperation of "the enemy" - one side alone can have a mobile firing control station which parks up (assumes a fixed position) and broadcasts a DGPS signal in addition to other CnC comms to missiles that it fires and controls.
> My understanding is the military has always had access to multiple GPS frequencies,
They've also planned for continued functioning as best possible in case of full and|or partial loss of GPS frequencies.
To recap, there's always been a coarse L1 GPS signal - that was delibrately made worse until 2000 by the addition of a keyed random clock error that required a daily key to revert (Differential GPS could fix that for anybody, the US Coast Guard broadcast a DGPS signal to "fix" that), there's always been a second L2 frequency that dual frequency users with both the coarse L1 daily key and the additional L2 key could use to improve accuracy with dual frequency tricks .. and, again, Differential GPS could improve that even more (by eliminating ionospheric errors, etc) - by the magic of Kalman Filters.
It's mainly focused on civilian (and US Coast Guard who apparently weren't "military enough" or something <shrug>) efforts to get military grade GPS via their own DGPS adventures ... but it was also the case that even the US military with dual channels and all the keys to enable real time reversal of broadcast errors could also benefit from increased accuracy via local theatre broadcast DGPS.
Do I have sources for the US military use of DGPS in the late 1980s and 1990s?
As an Australian involved in international high precision surveying I have vague recollections of articles stating as much in Scientific American type journals of the day and various AGSO publications .. anything else that I might of seen via some kind of five eyes agreement I'd have to really dig about to find and then dig even further to find if it's now in the public domain .. way too much work.
> Do I have sources for the US military use of DGPS in the late 1980s and 1990s?
> As an Australian involved in international high precision surveying I have vague recollections of articles stating as much in Scientific American type journals of the day and various AGSO publications .. anything else that I might of seen via some kind of five eyes agreement I'd have to really dig about to find and then dig even further to find if it's now in the public domain .. way too much work.
After thinking about the range of DGPS and how that would impact how it would be used, I googled "himars dgps" and found this:
> The Defense Science Board 1998 Summer Study Task Force on JOINT OPERATIONS SUPERIORITY IN THE 21st CENTURY
> ...
> As previously discussed, it will be possible in the 21St century to develop and globally deploy a military DGPS capability to any conflict area. The DGPS will contain anti-jam and other unique features to provide high assurance of signal availability and accuracy. In addition, the United States will have collected and updated global digital terrain elevation data (DTED) to 1-3 meter accuracy. The combination of real-time DGPS, digital terrain data, and highly accurate, space-based imagery (electro-optical/infiared/SAR) with ground moving target tracking capability, would make it possible to register fixed and moving targets on the battlefield to submeter accuracy. Rapid registration updates would also be possible using the dynamic collection capability of space-based imaging and tracking systems augmented perhaps with high altitude, long-endurance (HAE), unmanned aerial vehicle (UAV)-based sensor systems.
> This registration and DGPS now make it possible to consider new families of high precision munitions such as the DGPS-guided SPB. As target location error is driven to submeter accuracy, even smaller and lighter but lethal, high-precision weapons could be possible.
> ....
> This capability was demonstrated during an effort undertaken in 1993 to investigate the possibility of achieving a three-meter CEP impact accuracy for the JDAM product improvement program. The technology inquiry pursued two possible solution sets: seeker improvements and/or navigation guidance improvements. Given that seekers have certain limitations, the navigation guidance improvement path was pursued. Two possible solutions to improve
navigation error were considered: the civilian DGPS system approach or the military dual-frequency GPS receivers. The DPGS system employs pseudorange corrections generated by a GPS reference receiver. This approach is limited in range since the user must remain within line of sight of the ground receiver. In contrast, the military GPS receivers are capable of using ionosphere-free pseudorange measurements that extend the range to greater than 1,000 miles. In this case, range is a function of maintaining visibility with the satellite that is receiving corrections fiom a regional ground station.
> Using the latter approach in an Air Force-sponsored Joint Direct Attack Munition System Program entitled "Exploitation of DGPS for Guidance Enhancement (EDGE)," four ground stations were emplaced more than 1,000nm fiom the Eglin Air Force Base test range. Navigation corrections from the distant network were uploaded to a modified GBU-15 -a 2,000 pound glide bomb. In a release at 25,000 feet above an overcast, 1.4 miles from the target, the unpowered weapon hit within 2 meters of an aim-point.
> 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.
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.
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?
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.
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.
