RTK solution is not stable

Q&A forumCategory: QuestionsRTK solution is not stable
Daniel Korthauer asked 4 months ago

I have made some tests and the RTK solution in fixed mode is not stable and falls back to float. Also if in fixed the position is sometimes jumping by about 50cm as can be seen in the attached pictures. Another thing I dont fully understand is why the receiver is outputting DGNSS points in between.
Information to interpret the pictures.
red: single
yellow: rtkfloat
green: fix
blue: DGNSS
HW: ardusimple simpleRTK2B x2
FW: 1.11
Thanky you for your help.

Plot of GPS postionRTK position showing only Fix

7 Answers

It looks strange, the FIX solution is unstable, I doubt the quality of input correction data (RTCM) :
+ How far is the distance from Rover to the Basestation?
+ Where are you using Rover in? Is there any object, high voltage line, building, above or near Antenna and F9P of both Rover and Base?
+ Please check the connection cable (antenna, UART, Power).
+ You can provide log file of RTCM input data and NMEA output data ? (You can use U-Center to do that.), it will help the RTK analysis better. 

dkort answered 4 months ago

Thank you for your quick answer
+ the rover and basestation are relative close together ca. 20 cm
+ These test were done static without an actual rover. The vie of both receivers / antennas is free in almost all directions except for south east were an staircase entrance is blocking the view from the horizon to about 20° above horizon.
+ the receivers were connected to the pc via the ublox integrated USB port and the micro USB port of the simplertk board.
+ the log file of the NMEA data can be provided. unfortunately I am not able to provide an log of the RTCM data and I am not able to da another test due to weather reasons.
Here the links to the Basestation NMEA data and the Rover NMEA data

I spent nearly an hour watching NMEA messages of both Base and Rover with U-Center.
The signal quality is quite good and similar in both Base and Rover ..
This is a static experiment.
The number of satellites used is between 20 and 25. Including Beidou + GPS + Glonass + Galileo.
The FIX quality of the first 15 minutes is pretty bad and there is little improvement in the last 5 minutes.
I don’t see anything unusual in the message NMEA you provided.
We need more testing than this and hopefully it will be better, keep reporting your result !.

amorosik replied 4 months ago

When you write “..the FIX quality of the first 15 minutes is pretty bad..” what mean exactly?
Where you can see a FIX QUALITY?

It includes: keep time in FIX solution (Age) + position stability at FIX solution ( for Static Survey ) + position accuracy at FIX solution.

Selective answered 4 months ago

Just so you know, Galileo is down, all satellites.
I also had some weird behaviour, when I realized no Galileo was present.

Wait ..What do you mean with ” all Galileo satellites is down ” ?

Selective replied 4 months ago

Read the statement, the satellites are not working at the moment.

Its stracking in all time  in your device ,we have E13,E15,E21,E27,E9 for galileo
ESPrtk answer user Ardusimple forum