This’s gonna be tough.
Ardupilot can basically work with any GNSS that outputs NMEA and has UART. There are some chips, like the SkyTraq one, but according to this thread here it has some issues possibly with weaker design or low NMEA update rate.
There are however some other chips I found in my research, but I didn’t keep track of all of them because although they support NavIC, they don’t support RTK using NavIC in any configurations. Some examples directly from Ardupilot Docs would be Ardusimple simpleRTK3B Pro, which uses the Septentrio mosaic-X5 module, which is really expensive, and also Septentrio AsteRx4 RTK, AsteRx-m3 Pro/Pro+ boards.
Other ones would be:
- Allystar (TAU series)
- Quectel (L89, L79(A/C), L29(B,C), LG69T(AA/AP/AB/AD))
- Telit (SL869T3-I, SE868SY-D)
- NTLAB NT104 etc.
Most of the good ones are really expensive (~$800+) because they are multi-constellation and often come with RTK. Yet there’s no point in buying them if you want NavIC because none of them can use RTK with NavIC. At this point, I’m trying to design our own module to make it cost-effective. Honestly if I could just find a good and cheap chip, I would somehow make it work with AP instead of looking for a directly compatible module.
There’s also been some news about chips by Dhruva Aerospace at IIT Madras, but I couldn’t find much information about getting them. It’s a relatively new field so it should take time for good chips to come out.
Edit: These (ones listed in bullets) are again modules, and not recievers. Finding a reciever based on these would be another challenge if that’s what you’re looking for.
Edit 2: Apparently SkyTraq chips are worth a try according to this thread. PX1125R even supports RTK on L5 (though not S) so that’s another reason for me to try it out.