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.

I've seen some multi channel GPS front ends like this one: https://www.crowdsupply.com/amungo-navigation/nut2nt-plus

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.