Poor results in PPK using CORS station to correct Base

Hi –

I’m using two RS+ to survey GCPs for a structure-from-motion survey. I’m having issues getting good PPK results for our base station on two of our three survey days.

My workflow is as follows (based on an excellent guide I found here: https://documents.cast.uark.edu/emlidreach/Guide3.html):

  1. Download log from base station (RINEX 3.03).
  2. Download CORS data for the same time period from https://www.ngs.noaa.gov/UFCORS/
  3. Download .clk data from https://cddis.nasa.gov/archive/gnss/products/
  4. Run rtkpost with the base station as a rover and the CORS station as the base station.

I am unable to get anything better than a Single solution (Q=5). My suspicion is that the baseline is too long (this particular site is right between two CORS stations), but I wanted to see if anyone else had ideas. I’ve messed around with the satellite angle in the settings and changed the SNR mask, both of which made the solution worse. I’ve put a .zip with my .obs and .nav files, the .clk file, the .21o file from the CORS station, and the .sp3 file here: Base Data

Thanks in advance for any insight!


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Hi @sweeneyk,

Thanks for sharing the data. We’ll check them and write you back.

Hi @sweeneyk,

May I ask you to provide access to the folder with the data? My request should be delivered to your mailbox.

Hi Kristin,

I processed the data you provided in our version of RTKLib and got 100% in Fix with the Combined mode. If you use another version of RTKLib, please check if the issue persists when you use our RTKLib-QT.

I processed your data with the RINEX header base position set in the Positions tab. If I get it right that you enter the base position manually to get absolute accuracy, please note that you will need to enter the precise geographic coordinates of the CORS in WGS84.

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