Implement the ability to do PPK processing for tagging aerial image data

[DroneWuKong]

Describe problem solved by the proposed feature

This was started with this little guy:

PPK Improvement Discussion #22169

But I'd like this to be implemented for all capable GPS units, but at least the F9.

Currently there are 3 methods of achieving inch level accuracies geospatially. Most already know RTK. But in the aerial mapping side of things, PPK offers the ability to achieve the same if not better accuracies than RTK, with much less hassle and need for equipment and subscriptions.

With PPK there are no live connections needed, as the rover is saving ALLL the data, as is the base station. For it to be post processed after the flight in the office. Eliminating reliance on outside parties which can cause issues out of your own control.

Describe your preferred solution

Implement a way of saving the raw GNSS rover.obs data along with timestamps via json, to be used for post processing.

Describe possible alternatives

Currently there are only 2 GNSS units that are supported by PX4 that allow PPK processing. The Septitrio and the CUAV PPK unit, both of these save the data to onboard storage on the GPS unit.

If this is able to be done with out that need for a "special" gps, it would provide the aerial mapping/surveying world a great deed.

Additional context

#24188