PPK with only base logging?

Apologies if this has been addressed elsewhere, but I haven’t found any direct explanation for the particular workflow I’m hoping to use.

I’m working on a project where I need to map multiple sites with my drone, often without service, while requiring a relatively high degree of accuracy (<10cm). I have two RS+ units and a multi-spec sensor that can receive RTK corrections (SlantRange 4+ with navigation module). Unfortunately, I cannot extract the logging data from the drone as far as I can tell. I can, however, send corrections from one of my RS+ units and get a fixed position via RTK. Additionally, I cannot set ground control points because the areas are sensitive to disturbance.

I won’t always have internet access, so I would like to develop a PPK workflow that I can rely on in the field. My idea is to launch my base station in an averaged single solution and send corrections to the drone to get precise but inaccurate locations for the photos. Then, once back at the office, I would use PPK to find a more accurate position for the base station and shift the images based on that correction.

My flights will be within the Santa Monica Mountains, near Los Angeles, CA. So there are CORS stations nearby that I can potentially use. I’m also curious if I could get away with logging both of my RS+ units in a static positioning mode and correcting based on that data alone.

Does that sound reasonable? Can you shift all fixed positions by some correction factor? And are there better ways to find the precise location of my base station (PPP being an example)? How would you go about this?

I’d appreciate any feedback, suggestions, or reality checks you all might have. Thanks.

If you can find survey markers very close to your sites then local markers for each of your site by RTK or PPK should work well. Since you’re using RS+, it would be critical to loop back to a known point and ensure you have the required accuracy. You can do your RTK through Emlid’s NTRIP caster if you have good internet, it’s mountainous so LoRa won’t do any good. If not possible, PPK should do the job.

Overall your plan sounds fine, I wouldn’t rely on PPP with a RS+ as it shouldn’t be expected to get you below 10cm accuracy.

You can absolutely set your RS Base up and log statically on the site you are mapping. You would then take your Rover and log in kinematic and survey your GCP’s. If you have a benchmark on the site and want to set your Base over that, great, but if not then you will simply do PPK processing on the Base unit first. Afterwards, you will then use it as a reference and enter the PPK coordinates of the Base unit when doing PPK on your Rover.

If you are using a drone with the Emlid M/M2 mounted, or an RTK drone (ie P4 RTK) then you can PPK the drone flight using the same RS Base log as a reference, just like you did with the RS Rover.

You should have no problem obtaining the log files from one or multiple CORS stations to PPK your RS Base unit.

If you just set your Base up anywhere and PPK that base, then you can still take your RS Rover and shoot one or more of the local benchmarks to make sure you are matched up.


Correction, I don’t think you can use the RS+ for an M2 or P4 RTK as they are dual frequency. Someone will have to verify. I know you can process only the L1 data but I don’t think you can use an L1 base for an L2 receiver?? Not 100% sure but someone else will certainly verify that.

Hi Kyle,

Welcome to our community forum!

Yes, your assumptions sound reasonable. But I’d not say there is a straightforward way. You can calculate precise base location by post-processing with raw data from CORS.

In this case, you need logs from your base and CORS. Then, you can post-process and obtain precise base coordinates in Emlid Studio. You can read our guide to learn workflow. However, consider that the single-band receiver baseline in PPK is up to 30 km (18 miles).

Then, you need to calculate a shift between averaged in RTK and post-processed coordinates. This shift can be applied to the drone’s RTK coordinates. But I can hardly help with further steps, as I don’t know how your drone provides these coordinates.

PPP won’t provide you with the needed results. Reach RS+ is a single-band device. So, the absolute accuracy with PPP will be about 30 cm.

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