M3E RTK or PPK with no base and only CORS

New M3E RTK user and can’t seem to find a clear answer. I’m using Florida’s FPRN CORS NTRIP network to provide the corrections instead of a rover base station. DJI docs say to turn off RTK in the settings if I’m going to use PPK, but I’ve seen elsewhere that the setting there doesn’t matter when you run PPK as it’ll just overwrite the data in the photos. But isn’t the point of using RTK on the drone so that you have accurate location info, but in the event fix is lost, running PPK will correct those issues? Or is running PPK not necessary if RTK is on on the drone?

Also, I know how to download the CORS data, but the FPRN website allows me to pick multiple base sites. Should I, or should I just download the nearest? FPRN support told me I should always use Auto_IMAX or RTCM3_IMAX (if that matters) and never Auto_VRS.

Emlid Studio drone processing step 2 ( Drone data processing | Emlid Studio) asks for rover RINEX. I’m guessing this actually means the drone? Then step 6 says nav from the base or rover. Shouldn’t this be only the drone?

Sorry if these questions seem basic, I just want to make sure I get it all right.

Here’s something to review. Emlid gas great documentation and methodology for use of their receivers and also with drones.

One suggestion I would make… whether you are using base-drone RTK or PPK, have a base onsite logging the same rate of data as your drone. Post processing short baselines will have a higher accuracy/confidence on your drones positions. I’ve stressed this before many times, always have a base logging onsite even if you’re using RTN or planning PPK.

Processing long baselines to surrounding CORS with drones will give you some headaches. Besides, most CORS only long data at 1 second intervals at best.

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Hi @scavendish,

RTK vs. PPK: It all depends on you. If the accuracy you get from RTK is enough, you do not need to post-process your drone data again. Otherwise, if you lose a fix during the survey, it’s a great solution to post-process your data in Emlid Studio.

Also, I know how to download the CORS data, but the FPRN website allows me to pick multiple base sites. Should I, or should I just download the nearest?

Emlid Studio doesn’t have the network adjustment feature yet, nor can it process the data with multiple base files. Please download the nearest station RINEX data. In general, the shorter the baseline, the better the accuracy you will achieve.

Emlid Studio drone processing step 2 ( Drone data processing | Emlid Studio) asks for rover RINEX. I’m guessing this actually means the drone? Then step 6 says nav from the base or rover. Shouldn’t this be only the drone?

Yes, the rover RINEX observation file is from the drone. You can use either of the two or both for the navigation file. Sometimes, the data from the drone’s navigation file is not complete, so we usually recommend using the one from the base.

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Thanks for the replies, this helps. We are not surveying, we are documenting road/bridge construction progress, and overlaying the CADD onto the ortho or point cloud, so we want to be within inches, not feet so we can see potential issues before they get too big. I think flying with RTK will do what we need, but if it looks like we can’t and need a better PPK solution than CORS, then I guess we’ll grab an RS2, we just have an RX at the moment, which won’t work as a base. Baby steps.

Are you using the RX to set GCP’s?

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Same question here: does your RX receive correction from a CORS base to collect GCPs?