Can Emlid confirm there are actual differences in these two projections (NAD83(CSRS) vs. NAD83) - see attached screenshots? I’m running into issues using NAD83(CSRS). When I compare my RS3-collected check points on-site (in NAD83(CSRS)) against LiDAR data also outputted in NAD83(CSRS), the difference in the vertical access is very large (hundreds of millimetres). If I convert the check points to NAD83 using Global Mapper, the agreement with LiDAR data (NAD83(CSRS)) is really good (<20mm). It could be an issue with the software I’m using to process the LiDAR data (DJI Terra), but I’d also like to rule out it being an Emlid issue.
There is DJI forum thread here that is relevant.
The forum entry on 2-20 10:48 is important, which is as follows:
Hello, I have noticed this issue a long time ago. In DJI Terra, you need to actually select the original NAD83 instead of NAD83(CSRS). According to my tests, NAD83 original is actually NAD83(CSRS) and NAD(CSRS) is … well something else around 1,5m off. I hope they are gonna fix this someday, it’s annoying.
NAD83 and NAD83(CSRS) are two different realizations of NAD83. NAD83(CSRS) is the current realization used in Canada.
Did I understand correctly that you have a Reach receiver and use the RINEX observation file in DJI Terra? I don’t have any experience with post-processing in DJI Terra, but do you manually input the precise coordinates of the base in the software, or do you use the coordinates from the RINEX header?
I use my RS3 as a base for the drone mission (arbitrary point), meanwhile the RS3 is collecting RINEX data while the flight is on-going. I submit the RINEX to NRCan and receive PPP coordinates/elevation when I return to the office, and then manually enter new base station coordinates in DJI Terra. The LiDAR data is then adjusted to the new coordinates and ellipsoidal height.
I see. Here’s the definition of NAD83 and NAD83(CSRS) according to NRCAN:
NAD83 has undergone several updates since we first introduced it in 1986. It has evolved from a traditional, ground-based, horizontal control network called NAD83(Original) to a space-based, dynamic 3D realization called NAD83(CSRS).
NAD83(CSRS) represents a dynamic 3D realization of NAD83(Original). Canada and the U.S. collaborated to redefine NAD83 in relation to the ITRF through a seven-parameter transformation using VLBI stations common to both systems. We keep NAD83(CSRS) aligned to the North American plate using the NNR-NUVEL-1A estimate of plate motion.
I read the thread you shared, and I’m afraid you would need to wait for DJI Terra’s fix on handling these two datums in their software.
