Community Forum

Need some assistance for Post Processing with Reach RS

(Yves Mensa Bonsu) #1

I need some assistance with something.

I have two Emlid Reach RS that I use to take GCPS for my P4P in the field.

They’re configured as a Base-Rover set up.

When I’m in the field I use M+ modules to get GPS coordinates that are accurate to 2cm to post-process in RTKLib.

I’ve tried correcting points in post processing but it never seems to work.

Could someone please assist me with tutorials on post-processing using RTKLib or recommend other software for post-processing of the points? And preferably the alternative software shouldn’t be one that requires Real-Time corrections in the field, since most of the places I’m surveying in Sierra Leone don’t have an internet connection.

P.S my closest CORS Station is in Benin and it’s roughly 1,400km away


Hi, i noticed you forwarded a message to me on twitter.
It might be better to assist you on the forum, other might benefit from it too.
Could you share .ubx file from base?
Could i assume you have control of the relative distance of base-rover and processing there?

(Yves Mensa Bonsu) #4

Thanks, I can’t upload my UBX files from the base as I’m new to the forum and can’t upload files. Is there any way around it?

(Andrew Yushkevich) #5

Hi @ymbonsu,

You can upload your logs to Dropbox, Google Drive etc. and share a link here.

(Yves Mensa Bonsu) #6

Here are the base ubx files

(Andrew Yushkevich) #7

@ymbonsu, can I ask you to clarify your issue?
Please, describe your working steps, hardware setup you use (2RS? 2RS+? M+ only?) and the result you want to get.

As for the CORS station, 1400km is far more than it’s possible to use for post-processing.
Do you have any geodetic points near your working area?

(Yves Mensa Bonsu) #9

I set up the base at a point and set the base options as LoRa same as the correction output on an output power of 10dBm and frequency 886.5 MHz. On my rover my settings were fix.
After i did all this and took my GCPs, after post processing with RTKLib i had erratic results. So i want to get those a bit more accurate.

(Ryszard Pażus (GeoDigitalGNSS)) #11

The easiest way is to check the quality of the session by the CSRS-PPP service. For your longest session starting at 9:55, everything is OK. The results are not bad either for a single-frequency receiver. It would be better if the session was not interrupted many times. This is probably the cause of the trouble.
Bonsu1000.pdf (966.2 KB)

(Yves Mensa Bonsu) #12

Thanks, but with my reference station that far away how can I get my base points corrected before taking my rover points, so when I use my RTKLib/EzSurv i can get my points accurate to 2cm.

Another question what caused the interruptions and how can I reduce them. I’m still finding my way around RTKLib but how do I get my points green, Since my precision is ok but my accuracy is off?

(Andrew Yushkevich) #13

Please, share your rover and base raw ubx logs so that I can process them.
You base logs look good.

Do you use the Survey tool for collecting GCPs?

Do you have any geodetic points with known coordinates near your working area (8-10km)?

(Yves Mensa Bonsu) #14

Sorry about that.

These are my base and rover ubx logs.
Yes I did use the survey tool to collect my GCPs but I don’t have any known coordinates near my working area.

(Andrew Yushkevich) #15

These logs are the same, base and rover should be different.
Also, they’re in NMEA format instead of UBX.
Please, use this tutorial to download right logs from the Reach.

As there’re no points with known coordinates nearby, unfortunately, it’s impossible to get absolute position of the base.
However, I think that there should be some geodetic points since I see the existence of such projects in your country.

(Yves Mensa Bonsu) #17

@andrew.yushkevich sorry about that will resend, but when I went back to check my results (with Q1 = 26.4%) I noticed when i clicked on the animation it showed all my points getting a fix after I took them, so what caused the single and the float points which had higher percentages ?