Hi all, I am new to using any surveying equipment and would like to see if anyone has any feedback on my current workflow for a basic use case, and also ask a few questions.
Use case
I have 2 RS2 units, one configured as a BASE, and one as a ROVER, with corrections via LoRa from the BASE. I am only concerned about accuracy for relative positions. My plan is to:
Set the BASE RS2 in a fixed position. Edit the BASE RS2’s Base Mode coordinate to average Single, and then fix that as a manual coordinate for the BASE location.
Using the survey function on the app, use the ROVER to take measurements of 3 positions, averaging only FIXed solutions. *I don’t have a tripod for the ROVER, and plan to place it on the ground (there will be some tree cover).
Export the csv file to my laptop and calculate the distance and angles of the line of sights between point 1 and 2, and point 2 and 3 (to check the line of sights are perpendicular to each other).
Questions
a) Based on the above workflow, am I correct to assume a relative accuracy of 7mm+1mm/km for the survey positions?
b) I plan to also save the data logs as a backup. What is the difference between using the position file log from the ROVER, vs post processing both the raw .ubx files from the BASE and ROVER using the “GPS post-processing” workflow and getting the output .pos file?
Your workflow looks good. I only have a few comments:
You don’t need a tripod for the rover. A survey pole should be enough.
Please note that GNSS receivers require some sky visibility to track satellite signals. Reach RS2 is a multi-band device that can work in challenging conditions with some trees nearby. However, even Reach RS2 can’t work under dense foliage.
Regarding your questions:
Yes, you’re right.
If the solution status during RTK was Fix, you can just take an LLH log recorded on the rover. There is no need for post-processing.
You really need to get it on a survey / rover pole instead of just placing it on the ground to avoid multi-path. I’d get a topo shoe/boot also for the rover pole if the surface isn’t hard (i.e. asphalt, concrete etc). The point of the rover pole will sink lower into the surface.
Hi, @dominic.lim ! Welcome to Emlid Community forum!
Complementing what @svetlana.nikolenko explained, I want to add information on determining your base coordinate.
If you want centimeter-level accuracy at the points you will collect with the rover, your base coordinate needs to be set to that precision as well.
Starting a base with the Average Single option, the defined coordinate will have a precision at the metric level. The coordinates obtained with your rover, even being FIXed, will also have a metric error because the coordinate defined for your base was obtained with an autonomous solution. They will have the same discrepancy vector in their positions as the base.
To set the base coordinate to a centimeter level, you have three options.
Receive real-time corrections with NTRIP protocol on your base receiver, getting a floating or fixed solution. This alternative does not need post-processing;
Hi all, thank you for your replies! Noted on determining the base coordinate if I want absolute precision and will look into getting a survey pole for the Rover (did not know about possible multi-path error, thanks).
On another note, my current plan is to write a MATLAB script to obtain distances between the coordinates output in the Survey csv file. The script will also calculate angle between vectors, using the coordinates as input. However, if anyone knows of existing apps/softwares that already have this function, please point me in the right direction!
Thanks for the tips! After looking around the forums, I managed to get what I needed from QGIS - will look into these softwares if I ever need more complicated use cases
