GPS satellites

[ngatimozart]

Here’s an article describing the utilization of earth’s magnetic field as an alternative to GPS. Although accuracy is 10 meters versus GPS’s 3 meters, this alternative should be less vulnerable to jamming and no worries about kit being destroyed.

The Air Force’s Latest GPS Alternative: Earth’s Magnetic Fields

Officials just launched a public challenge to help create the artificial intelligence needed to turn the planet’s magnetic fields into readable maps.

www.defenseone.com

Hmmm, I am a bit unsure about it. In the polar regions compasses tend to go a bit haywire. There are many localised variations in the earth's magnetosphere and even a volcanic eruption may be enough to change a localised field. 3 m accuracy with GPS? That's somewhat of an understatement. In part your accuracy is determined by how many satellites your GPS receiver can see / receive at once. At a minimum it really needs 3 and the more the better, and from memory I think that the maximum that it is able to see at any one time is 5. The thing about GPS is time and it's the time data and ephemera data encoded in the signals that's being used to determine the receiver's spatial location in 3 dimensions. Today you can generally get that down to about 1m. For accurate sub metre measurements you need fancier gear and a fixed known location to work from. I worked with gear that was accurate to +/- <1 cm and was used for surveying.

Yes we do have a problem with the probable loss of GPS, GLONASS etc., during a conflict and an alternative accurate navigation method will have to be developed. I think that something based in the quantum computing / particle /mechanics fields maybe the answer because it has to be small enough to fit into a warhead.

 

[kato]

For accurate sub metre measurements you need fancier gear and a fixed known location to work from.I worked with gear that was accurate to +/- <1 cm and was used for surveying.

Or augment GPS data with further systems like Starfire or EGNOS, typically ground-based supplement networks to GPS. Starfire in particular claims accuracies below 4.5 cm in mobile applications.

In the polar regions compasses tend to go a bit haywire. There are many localised variations in the earth's magnetosphere and even a volcanic eruption may be enough to change a localised field.

It's also rather dynamic, with the pole shifting by up to 35 MoA (!) within a year, local anomalies popping up and disappearing and the global intensity varying by up to 1% in a year.

 

[ngatimozart]

Or augment GPS data with further systems like Starfire or EGNOS, typically ground-based supplement networks to GPS. Starfire in particular claims accuracies below 4.5 cm in mobile applications.


It's also rather dynamic, with the pole shifting by up to 35 MoA (!) within a year, local anomalies popping up and disappearing and the global intensity varying by up to 1% in a year.

And the poles have a habit of flipping. I read something a whiles back that suggested that the current rate of pole shifting could be explained as a possible precursor to a pole flip. Can't remember where I read it, but that'll play havoc with a lot of things when it happens and just not anthropogenic things but other fauna that use the magnetosphere for navigation.

 

[John Fedup]

Breaking Defence has an article on some new kit which will be tested shortly for improving PNT. A new GEO satellite and some LEO satellites will be evaluated.

NTS-3, Aiming To Improve On GPS, Starts Integration Tests In August - Breaking Defense

 

[John Fedup]

Another candidate for a possible GPS replacement from Sandia Labs is described in the link. Quantum sensor technology is used. Although small, the vacuum technology requires some exotic materials and there are concerns about the power requirements. Still, encouraging, given the real threats against satellites.

Sandia's Atomic 'Avocado' Could Allow GPS-Free PNT - Breaking Defense

The first-of-its-kind device, a vacuum chamber for containing clouds of atomic particles that drive quantum sensors, is about the size of an avocado.

breakingdefense.com

 

[John Fedup]

This article summarizes some possible new technologies for PNT. The author also proposes that funds for future GPS satellite upgrades be shifted towards a coordinated program to replace GPS. Given the advances in jamming and especially spoofing, this idea has merit. Add in Chinese advances in quantum technology for PNT, the idea has even for merit.

LOST ON THE NEXT BATTLEFIELD: THE NEED TO REPLACE GPS

Most people don't understand how integral the Global Positioning System (GPS) is to the average U.S. citizen's daily life. The timing function alone touches communication systems, electrical power grids, and financial networks throughout the day. WAR ROOM welcomes Robert Hoffman to examine the...

warroom.armywarcollege.edu

 

[ngatimozart]

This article summarizes some possible new technologies for PNT. The author also proposes that funds for future GPS satellite upgrades be shifted towards a coordinated program to replace GPS. Given the advances in jamming and especially spoofing, this idea has merit. Add in Chinese advances in quantum technology for PNT, the idea has even for merit.

LOST ON THE NEXT BATTLEFIELD: THE NEED TO REPLACE GPS

Most people don't understand how integral the Global Positioning System (GPS) is to the average U.S. citizen's daily life. The timing function alone touches communication systems, electrical power grids, and financial networks throughout the day. WAR ROOM welcomes Robert Hoffman to examine the...

warroom.armywarcollege.edu

Yes, GPS is starting to become a liability now rather than an asset because we are so wedded to it. The most salient feature of GPS is its timing capabilities because they are the core component of its methodology. That enables the highly accurate spatial measurement in four dimensions; x, y, z, t, where the x, y, z axis are your normal three dimensional axis and the t is the time (or temporal) dimension. Each of the satellites measures its position on three dimensional space by celestial navigation. They sight on specific stars and can pinpoint their spatial position very accurately, especially because they are well outside the atmosphere and don't have to be concerned about atmospheric interference with the light rays. That's the second part of GPS. By calculating the differences in the time signals between the ephemerals (signal data) received from the satellites, the GPS receiver can calculate its position relative to the satellites.

So any new PNT system requires a way of accessing very accurate non terrestrial three dimensional benchmarks before it can even think about the rest of the system. Non terrestrial because everything on the surface moves; mostly very slowly ~ tens of mm per year for solid surface areas. Here in Christchurch we are moving horizontally WNW at 40mm a year, with the odd vertical lurch. In Wellington every few centuries they have a 6m sudden vertical lurch upwards. All of this is the result of plate tectonics and everywhere on the planet is subject to it. That's why a series of stars as benchmarks are the ideal solution. Yes are moving relative to them as well but that we can account because it's a known value and not subject to unknown and unpredictable geologic events.

But the $64 billion question is how to get that data or ephemerals to receivers that are insider buildings, subsurface, shaded, shrouded etc., and most importantly cannot be interfered with in any by an enemy? It requires some form of electromagnetic energy (EM) and as such if it can be transmitted using any form of EM it will be able to be detected as well. Another option is extremely sensitive accelerometers, but the further you travel from your last datum-point the greater the probability of uncertainty. It's certainly an interesting problem.