Event 38 starts Reach RTK equipped mapping drones delivery

I've just seen cool tests from Jeff Taylor and his Event 38. They integrated Emlid's Reach in E384/E386 mapping drones and verified processed data accuracy using data from Trimble R6 Model4. 

With the Emlid Reach RTK GPS Receivers now available, we’ve been conducting tests to determine their accuracy and working on the integration into the E384 and E386. The goal was to determine relative, or scale, accuracy as well as absolute accuracy verified with a survey grade Trimble R6 Model 4.

We post-processed the data in three different ways to explore the effect each would have on the resulting data. For PPK GPS processing, there is a receiver onboard the aircraft and another stationary receiver on the ground. The ground receiver (base station) is used to calculate corrections to refine the position of the airborne receiver. The base station also calculates a precise GPS coordinate for itself, with the option of writing in another, more accurate coordinate if desired. We constructed orthomosaics on the Drone Data Management System™ using geotags calculated from the Reach base station and the Trimble base station, using either the Reach base coordinate or the Trimble base coordinate. The combinations for each test are listed below.

Base Station Corrections Base Station Coordinate
Reach Reach + CORS
Reach Trimble R6-4 + ODOT VRS
Trimble R6-4 Trimble R6-4 + ODOT VRS

Test1:

It was clear straight away that there was an offset between the Reach and Trimble coordinates, so we focused on scale accuracy for this test. The offset is clearly visible in the image below, where emp is the Reach base station coordinate and 6 is the same coordinate shot by the Trimble R6. To measure the scale accuracy of the Reach-only orthomosaic, we measured distances between several pairs of GCPs in different directions. The error was 3cm in each case.

GCP Pair Reach Orthomosaic (m) Trimble R6-4 (m)
12-4 171.87 171.84 NE-SW
19-3 115.23 115.20 North-South
5-2 145.46 145.43 East-West

emlidmisalignment

Test2:

Processing the geotags using the Emlid Reach base station but using a coordinate shot by the Trimble R6-4 resulted in very good accuracy relative to the Trimble shot GCPs, with an RMSE of 3.36cm.

GCP Error (cm)
2 2.631
3 3.749
4 4.799
5 2.072
7 2.867

test6

Test3:

Finally, processing using the trimble base station for both corrections and the base coordinate yielded similar results to those obtained with the Reach corrections, RMSE 3.54cm.

GCP Error (cm)
2 4.667
3 3.099
4 4.189
5 2.104
7 3.075

test5

These results should be considered very preliminary, as there were a number of factors that could have adversely affected the accuracy. The Reach coordinate may improve once we are able to calculate it with a closer VRS. The mission was collected with a relatively high GSD of 3.5cm/pixel, so it is difficult to pick the GCPs accurately.

Still, there are some conclusions we can draw from this data. Even without a good base station coordinate, the Reach system can produce very good scale accurate results. When paired with a higher quality coordinate, the Reach can produce very good absolute GCP coordinates. If a fixed position can be marked once by a survey grade GPS, then it can be used as a reference point for all missions in the same area, forever. It may also still be possible to obtain similar results with the Reach alone using the VRS network or Precise Point Positioning.

We’ll run more tests to verify the accuracy, but initial results are very good. We’re now making the first deliveries of the Reach system to select clients before a wider release in the very near future.

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Comment by RPM on December 1, 2016 at 11:35am

Nice work guys thanks for posting the results. It would be cool to see some published coordinates observed with both to compare. Something I will be doing myself real soon. Cheers!

Comment by Jeff Taylor on December 1, 2016 at 11:37am

Thanks for posting, Dmitriy. This was just a first attempt with a lower resolution camera. We have it working now with the Sony QX-1 too. We're still putting together a case study, and working with some customers to get them upgraded but we should have it available to the public very soon.

Getting it to work on the QX1 was a pretty difficult job. We might also sell the cameras and trigger/feedback circuitry if there is any interest.

Comment by Jesus A on December 1, 2016 at 11:49pm

Is QX1 still in the market? Seem to have been discontinued.

Comment by Jeff Taylor on December 2, 2016 at 7:01am

I think it's still being sold in Asia. The inventory for digital cameras tends to stick around for a while even after the camera is dropped, in my experience.

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