[FOSS-GPS] Differential GPS with RTKLIB 2.4.2

Gordon Williams gwilliams at ncf.ca
Thu Jun 6 13:01:58 PDT 2013


Likely a setup problem or some bug, but could one antenna be affecting the other antenna at such a close distance?  What happens if you move them 2m apart?

This is something that I want to try once I get my second ublox datalogger working, so I hope that you will provide some feedback on what worked for you.

Gordon Williams

  ----- Original Message ----- 
  From: rolf.elsing at online.de 
  To: foss-gps at lists.osgeo.org 
  Sent: Wednesday, June 05, 2013 11:23 PM
  Subject: [FOSS-GPS] Differential GPS with RTKLIB 2.4.2


  I’am trying to build a differential GPS using RTKLIB 2.4.2.

  The accuracy that I can achieve is around +/-2 m.

  Which is about the same that one of my sensor achieves in PPP kinematic mode.

  My expectation is to achieve something around +/- 5 cm.

  The set up:

               Sensors                                2 UBLOX NEO6P 

               Antenna              Trimble Bullet III

  The sensors are installed on the roof with a free 360 °view. RTKLIB indicates that 6 to 8 Satellites are visible. The distance between both sensors is < 20 cm.

  Ublox Center Configuration:

                  NEMA Child Messages Disabled

                  UBX Child Messages Enabled

                                  RXM-RAW Enabled

                                  RXM SFRB Enabled

                                  RXM-RATE 200ms

                                  Dynamik Mode Pedestrian

  RTKLIB Configuration

  Input Streams

                  Rover Serial COM 1, UBLOX

  Base Serial COM 2, UBLOX

  Log Streams

                  Rover to File

                  Base to File

  Solution Log

                  Solution 1 toFile

                  Solution 2 to File



                  Base Station Position is acquired by 10hour static measurement.

  So, with this setting I usually get FLOAT (90%) and intermediate FIX (10%) soloutions with an accuracy of +/- 2m.

  My expectation is to achieve something around +/- 5 cm.

  Is my expectation wrong?

  Have I selected the correct configuration?

  When I run the sensors stand alone in PPP Kinematic mode I also get around +/- 2m accuracy which matches the manufacturer provided data.  So I assume that my Antenna, Sensor are working fine.

  Can somebody HELP ?


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