GPS is one of the most amazing technical onions I've ever dealt with. I've just been scratching the surface of it with understanding positioning for a robotics project. I kind of wish I had an opportunity to do more paid work with it. But it seems to be the realm of PHDs.
One of StarLink's biggest overlooked opportunities I think is radically re-engineering a GPS like system that can work indoors and outdoors as well as offering some pose estimation capability. It would make implementing robots way easier.
Well, this is embarrassing. MvB's title says 100 episodes but he has completed 18 as of this time. I had only gotten to Ep. 15 so I didn't twig to the work-to-go until just now.
I'll update my original and check out the Stanford course as well.
The technical side alone is unbelievably interesting, but when viewed in the context of military mapping/ navigation history and cold war geodetic / geospacial IBCM targeting, it goes all the way down the rabbit hole.
I took an undergrad course in GPS at Colorado School of Mines and enjoyed it immensely.
We didn't work on the radio level (other than learning about the 2-frequency ionosphere delay measurement as a calculation input), but did the rest of the stack above that including working out programs to derive position from given data input. I was a civil engineer but I think it's a great cross-discipline subject for a lot of fields.
You would need to get a facing direction. Most robots are doing that with a magnetometer, gyros and an extended Kalman filter. This has quite a few disadvantages though. First and foremost the magnetometer which is really your source of truth is unreliable. It wanders constantly and frequently your Kalman filter will start up in a bad state.
With 3 or 4 channels you could use the GPS almanac to get satellite direction and your heading. Though you could do it with two if you could get two antennas a couple of feet apart. But smaller robots don't have that kind of room.
Right now I think the biggest pain point with GPS is that if I want single redundancy GPS with 2 CM precision and true heading I need a whole bunch of stuff. 2x 200$ GPS receivers (ublox f9p) on my robot. 1x 200$ receiver with a decent antenna and a xbee radio to act as a RTK base station. And this was just for a simple outdoor rover. And the base station always had to go in the same place because you have to do everything relative to the base station. Then you need all the software to coordinate all that and manage everything.
I want 1 receiver unit, global absolute position within 2 CM with a true heading. Additionally, I want seamless transitioning/augmentation with a global network of terrestrial beacons for interiors and areas with poor surface coverage. And I want all that in a 100$ish module and some sort of subscription.
Have you looked into using gyros for north-finding? There's been a lot of progress in recent years with MEMS gyros (which normally have too much zero-drift to work with traditional gyro north-finding techniques).
That's a pretty neat technique. It seems superficially similar to how mems magnetometers work. The size and oscillation make me question how robust that is though.
One stop gap solution I has was just an IR beacon on my GPS base station. I got an initial alignment with the rover camera and my two gps points. But ended up adding a second gps to the rover.
One of StarLink's biggest overlooked opportunities I think is radically re-engineering a GPS like system that can work indoors and outdoors as well as offering some pose estimation capability. It would make implementing robots way easier.