Post-processing results lack precision

Emlid Studio Static / Kinematic processing
1

I collected point data on GCPs using the RS3 for the rover and RS2+ for the base and received corrections using the LoRa. I left the base out for at least 45 minutes (Average SINGLE) before collecting these points. Each point was collected when the FIX was actively working. The results of the RTK alone were about 2-5ft from the GCPs when we brought them into QGIS and the projections are all uniform.

I used two different strategies for post-processing:

  1. Using the static processing I used a nearby CORS station to correct the position of the base. I then used the delta lat and long to correct each point location.

  2. I used the stop and go method to correct each position.

Both of these methods resulted in the points being 2-5 ft from the GCPs. While I understand the points may not overlap exactly with the GCPs, I expect a more uniform level of error. What might be causing this issue?

3

Hi @katie.kennedy,

Using the static processing I used a nearby CORS station to correct the position of the base. I then used the delta lat and long to correct each point location.

Measurements collected in Single are in the WGS84 datum. Could you please tell me where the data was collected?

If it’s in the US, then the Static Processing results will be in NAD83(2011) datum, which when you computed for the shift between the new and old positions, would explain the 2-5 ft distance from the GCPs.

I used the stop and go method to correct each position.

When you did the Stop and Go, did you input the precise position of the base? The base position in the RINEX header is the last averaged epoch coordinate, which is accurate to a few meters.

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4

I am in the US! and I used the header position. Thank you for this insight! Is there a way to transform the WGS84 datum to the NAD83 datum?

5

Unfortunately, the transformation from WGS84 to NAD83(2011) is not straightforward. Others have suggested using the NOAA HTDP tool to transform the positions from WGS84 to NAD83(2011).

The easiest way to update the position of the GCPs is to post-process your Reach base in Static using the nearby CORS. Then, drag and drop the resulting .pos file into the Base field during the Stop and Go PPK.

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7

Which WGS84 reference frame is specifically used for Single measurements?

9

Reach uses WGS84 (original) realization.

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