Wrong in Post processing method in docs

Dear All,

I’m trying to do post-processing of reach data using base and rover. While going through the GPS-Post processing topic, I have seen that it is wrongly mentioned as “Calculating base position” at one place (screenshot1 attached). Actually, it should be for the rover. There are no details given on how to get “base position” in that manual. Also, it is valid for obtaining “relative positions” of the rover as the document says we need select either "averaged from single-point " or “RINEX header position” for the base station (screenshot 2)

There is no mention on how to get base position accurately (either by PPP or from CORS reference station) in this document. It would be better if anyone can provide such details.

In India, we don’t have CORS station or any GPS station (no standard reference stations are available). In that case, how can we get an accurate Base location? to cm level.

best regards

1 Like

In that case, you will have to do PPP. I will suggest using NRCAN.

Setup on the point and log at least 6-12 hours, though more is even better.

Depending on how quickly after collection you submit the data, you can get 3 types of solutions: ultra rapid (<24 hour after submission), rapid (>24h<2-3w), and final (>2-3w).
Final will give you the best result, but at the cost of waiting quite a while. Longer logs will partially mitigate this, but final is just better.

When converting your ubx to rinex in RTKconv , choose the v2.10 standard, especially if you are using an RS2.

1 Like

Thanks, @wizprod. WE have max 2-3 hours of base logs as of now. We will log the data for at least 12 hours and try with NRCAN. What do we need to do if we require mm precision & accuracy in such a case? Or is it not possible!.

In our case, we are using Reach M (2 nos) and one Reach RS for beach surveying (elevations). Most of the time we are keeping the base station at the same location. What happens to the position and height measured by the rovers if the base is shifted? Will the rover position (and elevation) also get shifted? In that case, what we need to do to get good results. Will PPP of base data at different times help?

And also, what is the maximum baseline between base and rover is suggested in PPK? I learnt that around 10 km for RTK? Is it same or even greater distance is also enough. Kindly suggest.

I have tried with the Multifrequency RS2 and a 18 hour log. Rapid was 1-2 cm, final was 7 mm.
When I tried when the RS+ for close to 24h I think I got 3-4 cm on a Rapid.

If you input all the right coordinates and height, then in theory a static rover should indicate exactly the same position.

I have tried 100+ km baseline, but the recommendation is no more than 30-40 km for L1. Also remember that the longer the baseline, the more error you will have.


@wizprod… which software did you use for PPP processing. Have you used RTKLib?. Today I came to know that we (in India) have some GPS reference stations at around 500 km. How to process in PPP with this data? If we have multiple reference stations data… is it possible to give all the data while processing? Any help is heartfully welcome.

I have no experience with PPP in RTKlib.
I have extensive experience with RTKLib for PPK however. 500 km would be way too much for PPK.

There are some programs that can do virtual basestations from multiple other stations.

I still think your best option is to submit a long observation to i.e. NRCAN.

try Auspos or csrs-ppp, they are online free service. You enter a dual frequency rinex and you get a nice report with absolute location.
Be carefull : absolute location is very often disconnected to national grids.

1 Like

But I’m using L1 Reach RS…

Can’t we use 500 km reference station to get a PPP solution for the base and later use this co-ordinate for PPK with known base station in our study area?

You don’t need any reference station for PPP, that is the beauty of it.
Remember that PPP is not the same PPK.

PPP = Precise Point Positioning
PPK = Post Processing Kinematic

try csrs-ppp, it is working with L1 rinex, but much less accurate

This topic was automatically closed 100 days after the last reply. New replies are no longer allowed.