[FOSS-GPS] RTKLib rover - base question

[Osterman, Aljaž]

Hi,
Today some rain was forecsted which I feared as I'm working outside with my laptop but still I managed to make some progress.
1- I switched off all messages except for RXM-RAW and RXM-SFRB. Now streams generate files of approx. equal size.
2- I checked protocol_out which was set to UBX so this was ok.
3- got data from nearest national GPS reference station

I managed to get approx. +-2 m precision with ppp static mode, with static mode and national ref. data I got +- 1m. In single mode, it was probably +-10 m.
Now I have a few questions: As I understand the theory even solutions in ppp static mode (for a receiver that doesn't move) don't converge with time towards a real position? So I still need to make average to find it?
The next question is about finding real location coordinates from solution data (multitude of points). Is averaging ok or perhaps is there a tool in RTKLib? What should I use to correctly determine coordinates of a base station?
Another question is about calculated digits of position coordinates. For example, national reference station has position set to 6 digits while RTKNavi displays 8 digits (after decimal point). So the last 2 how meaningfull are they?

Already looking forward for your replies :)

With best regards,
Aljaz

________________________________________
From: foss-gps-bounces at lists.osgeo.org [foss-gps-bounces at lists.osgeo.org] on behalf of Daniel Kranich [daniel at NUSalaska.com]
Sent: Tuesday, July 24, 2012 7:03 PM
To: foss-gps at lists.osgeo.org
Subject: Re: [FOSS-GPS] RTKLib rover - base question

See Comments Below
On 7/24/2012 4:44 AM, Osterman, Aljaž wrote:
> Dear all,
>
> I've received several comments from different people. Thank you. Unfortunately there is still no solution to my problem.
> As proposed I tried several things:
> 1 - applied latest patch
> 2 - took base station data as correction input
> 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.
Ok so if you want to just run a single rover, you should use PPPstatic.
That will give you best precision with no base station.

However, if you have a base station then you should try the following:
1) start up RTKnavi on the base station computer and run the PPPstatic
for 12-24 hours. Then take the final coordinates and write them down.
(dont move your base station antenna as you have now determined the
location of your base)

2) run strsvr.exe on the base station computer. set the input as you
would for rtknavi. then set the output as TCPserver and put in a random
port number. I used 5000. figure out the IP of your base station computer.

3) plug your rover into your rover computer. start up RTKnavi on your
rover computer. set up the rover for a Single solution. Also turn on the
base station and select TCPclient as the input type. Then for the option
add the ip of your base station computer and the port you set.

4) go into the options and under the "Positions" Tab. The lower half is
where you can input the coordinates of your base station. If you are
using degrees and seconds then use the "Lat/Lon/Height (deg/m)" or if
you have degrees that are decimal then use the "Lat/Lon/Height (dms/m)"
and the others are rather self explanatory. You dont need to mess with
the antenna Type.

5) Start it up and see how it works.
> 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 ...
> 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?
>
> 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.
not sure why this would happen...
>
> 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.
This happens to me also, however it doesnt seem to be much of a problem
>
> And I still haven't obtained the coordinates to fix the position of my base.
follow steps above for this
>
> Regards,
> Aljaz
>
> ____________________________________

Best Regards,
--
Daniel Kranich
Northern Utility Services

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