Not exactly Ardupilot-based, but Ardumower;-) But I’m using a pair of UBlox ZED-F9Ps (as base & rover - ardusimple boards with direct 900MHz link) and pretty consistently get within 2cm;-)
My base station is on our roof, so the baseline is always < 100m 
I recycled a RasPi2 with GitHub - Stefal/rtkbase: Your own GNSS base station for RTK localization with a Web GUI to forward data to rtk2go as well.
For les than the price of an F9P there is the UM982.
I’ve ordered one, alas on paper it looks like a good dual antenna heading solution in one module.
Seems like ardupilot supports it and holybro has a “package”
H-RTK Unicore UM982 (Dual Antenna Heading) – Holybro Store.
I did a rover based on a pair of F9P and it removed ALL of my compass issues…
(Not Ardupilot, wrote the rover pilot from scratch for that project)
That’s cool! My hope is that the CORS system is “good enough” to get started and save me from building a base station from the offset. I like to take my drinks from the fire hose in gulps if I can.
I reeeeally hope I can get good enough precision from NTRIP to get started out. I am sure I will set up a base station at some point. I’m in the middle of the woods and that precision would be nice.
I highly doubt you will be able to produce results that are better than a state funded survey system by configuring your own fixed base.
You would definitely think so.
While I agree the State reference station is hard to beat for accuracy, I found that getting GLONASS added into the mix - and L1 & L2 - greatly improved the ratio of FIX vs FLOAT.
If your local government funded reference station has more than one constellation, bravo.
The NOAA website provides historical observation data, often even for CORS systems that are subscription-only for real time use.
I picked the Columbus, OH site (central to the state) and grabbed a 1 hour sample from yesterday. The RINEX data shows GPS, GLONASS, and Galileo reception across L1, L2, and L5 bands. So the Ohio CORS system seems fairly robust (assuming it’s similarly configured statewide).
Some NTRIP’s might not use all the satellite constellations that your rover uses. If that is the case, you will probably want your own base that uses the same constellations as your rover.
I didn’t research this much, but thought a fixed base station was the way to go for the most accurate corrections - not true?
If NTRIP is better, I’ll pull that antenna off the roof and use it for my next project.
@Yuri_Rage , did I hear you correctly - NTRIP is more accurate than fixed base for corrections? cd…
No. Read the full thread.
Corrections are only as accurate as the source, and do not conflate accuracy with precision.
Ok - just re-read. So my base station corrections are more precise than NTRIP corrections (because the NTRIP station is farther away?) and, assuming my base station has been running for a few days, my position of the base station is accurate enough.
If no, just tell me to keep reading - have read this thread several times - the nuance between accuracy and precision is making it’s way slowly into my brain…cd
Still not quite. Still conflating accuracy and precision. And no grasp of survey-in vs TMODE3 operation, nor the possible inaccuracy of survey-in that I laid out above (that also DOESN’T MATTER!).
You’re chasing your tail. Focus on tuning your machine, not on GNSS nuances.
Will do - seems to be running quite well - today I mowed around 2 acres. When it was going slow, it wasn’t going very straight, but after increasing the speed a little - hums right along. Now, to go around some trees and work out how close I dare to get to my fences/buildings. Will probably mow that with the tractor/shredder for now.
Grass on the runway is about 2 in tall - should be ready for first mow near the end of the month. Thx for all the help, and if ever in Austin, pls reach out…cd
When I started this thread the nearest (free) NTRIP stations were in the next state. I want to avoid setting up a base station at the beginning to reduce the complexity of my first build. As it turns out, Ohio grants anyone free access to the CORS (NTRIP) network and I am surrounded by base stations with antennas that appear to pick up every GPS constellation. If it turns out that they are “good enough” I can concentrate on setting up my machine (now going through Chinese customs 
) without the headache of setting up a base station.