[FOSS-GPS] RTKLib rover - base question

[Mauro Ugarte Avilés]

Hi Aljaz,
> As proposed I tried several things:
> 1 - applied latest patch
Not so necessary, without any patch RTKLib had correctly decoded and 
processed u-Blox LEA-4T and LEA-5T observables (RXM-RAW) and navigation 
data (RXM-SFRB) since 2.2.2 version (as far as I tested).

> 2 - took base station data as correction input
Corrections (mainly RTCM-SC104 protocol) have another format entirely 
different to RXM-RAW, RXM-SFRB (observation and navigation) messages.

> 3 - recorded input streams for rover and base
>
> I changed the hardware set-up to simplify the case. Now both receivers are connected via usb to my computer. They don't move. My first question is which positioning mode should be used for evaluation/best precision?  DGPS/DGNSS, Static, Fixed ...? I hope my questions are not too stupid.
If the rover receiver is not moving, you should go with all the 
defaults, "Static" Positioning Mode and "Continuous" Integer Ambiguity 
Resolution. You can't get results if you don't set a position for the 
receiver's antenna acting as base.

>   
> I tried some modes but results were strange meaning that normally the solution was only single but for example with fixed mode position went to N 89 59 59.99 E 180 00 00 H -6335368 ...
"Fixed" means that the rover is in a fixed and exactly defined position. 
Those results (N 89 59 59.99 E 180 00 00 H -6335368) are the defaults 
for the rover's antenna position.
> Can anybody comment on #2 above? Is this a correct way or are base data meant to be used as input stream for base station?
You are right. Base data is meant to be used as input stream for base 
station.
>
> Finally, I logged streams from rover and base. I was able to open and display both with u-center. With RTKPost I successfully opened the one from rover but the other from base contained no data after transformation (file .pos has only the header). Interestingly the original ubx files  for rover and base had different sizes (for the same length of time): rover - 1605 kB, base - 447 kB.
Both should be of equal size, or at least very close. Maybe you should 
check the MSG (messages) settings, on the "Configuration View Window" at 
u-Center for both receivers (deactivate message by message on every 
port, to finish activating JUST RXM-RAW and RXM-SFRB). Right now I was 
connecting our LEA-5T u-Blox receiver with RTKNavi, to recall that the 
correct output protocol to use IS NOT "RAW", BUT "UBX" OR "UBX_NMEA". 
Maybe that's the main issue for you and for others that asked for 
similar help. Without checking it like I'm doing now, I recall advising 
others to set "RAW" as the output protocol for the selected port (I'm 
very sorry for that!!!). It's a 6T the one you are using right?.
>
> Also I noticed some strange behavior of RTKNavi. After some time of running it starts sticking - for shorter or longer periods of time there's no change in calculated position with no new points plotted. Afterwards it resumes (calculates and plots again). Normally if I stop and start the program again everything looks normal (as if some buffer gets full and needs to be emptied from time to time). My signal from satellites is ok so this shouldn't be a problem.
Never experienced this.
>
> And I still haven't obtained the coordinates to fix the position of my base.
Modify the protocol output to UBX, deactivate any other message that's 
not RAW or SFRB, and collect some data to generate a pos file for your 
base receiver (for testing purposes half an hour is enough). Then use 
the average or median position as the base station's antenna position, 
and try again.

Best regards,

-- 
Mauro Ugarte A.
Researcher - Electronic Engineer
Satellite Remote Sensing Laboratory
Optical Instrumentation and Information Division
Center For Optics and Photonics | www.cefop.cl
Universidad de Concepción | www.udec.cl
Phone/Fax: (56) 41-2204740 | mauro.ugarte at cefop.cl



--
   Este correo electrónico y  cualquier archivo adjunto son confidenciales
y son solamente para el uso del individuo o entidad a la que van dirigidos.
Si ha  recibido  este correo  electrónico por error por favor notifique al
remitente.  Este  mensaje contiene  información confidencial dirigida a la
persona  implicada.  Si  usted  no  es  esa  persona  no debiera diseminar,
distribuir o copiar este mensaje de correo electrónico.