Dears,

This is my first post here.

I am trying to post-process surveys I have done with two Emlid Reach. I am a beginner and even after reading the Emlid post-processing tutorial, https://docs.emlid.com/reach/common/tutorials/gps-post-processing/, I have doubts.

**My survey**

I did several point surveys in a remote area without benchmarks, with 2 Emlid Reach antennas: a **base B** and a **rover R**. The surveys are far one from another so I placed the B in different site for each survey. The surveys need to be joined and therefore I need to georeference all in absolute coordinates (including heights).

B did not receive any correction (I need to improve the understanding of NTRIP for the future surveys!) so I set it with â€śaverage singleâ€ť. I did not note the coordinates because I thought they would be stored somewhere in the logs (next time I will do it for sure!). R, connected to B, worked well with float average and fix solution.

I have up to date firmware and ReachView version.

To obtain absolute coordinates, I postprocess in static mode B with the **closest permanent station S**, working with S as base and B as rover. In this case I will obtain the absolute coordinate x_abs, y_abs, z_abs of B and, knowing the approximated (average single) coordinates x_rel, y_rel, z_rel of B (when I launched B), I can calculate the differences in coordinates dx = x_abs - x_rel, dy â€¦ , dz â€¦, and apply this translation to the survey operated with R.

I am using the RTKLIB suite to convert the logs in RINEX and postprocess. My B has a huge log (all life) so I need to trim to the time window of the survey (not trivial). Following the EMLID tutorial for my field configuration I have doubts related to the log files to be used.

When calculating base position with RTKPOST, EMLID suggest

a) Choose my B .obs file for the Rover field (RINEX file from your rover which is my B).

b) Select my S .obs file for the Base Station field (RINEX file from your base which is S).

c) Put B or S .nav file in the third field.

d) (Optional) You can as well add precise ephemeris and clocks at this stage. They are required for long baselines.

**Questions**

- Since R and B both have base and rover logs I am confused. Can somebody state which rinex should I use in a)? Rinex from *raw.ubx log coming from B or *base.RTCM3 log coming from R, or is the same?
- If I put .nav from B or from R or from S in c) I have different results. Which one should I put?
- What are precise ephemeris and in which format are given ? Are they necessary?
- Ideally, once the postprocess is achieved I would make an average of the postprocessed positions of the B coming from the .pos so that to have x_abs, y_abs, z_abs. Since I didnâ€™t write down the average coordinates of B, I can get the x_ave, y_ave, z_ave from the header of the base RINEX .obs obtained from the rover R. Finally I have the differences and I apply it to shift my points surveyed with R. Is it a correct workflow?

Any help is really appreciated!

Thanks,

Francesco