RS2+ Rover is over 1' off vertical on all points

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The vertical accuracy of my RS2+ Rover is off on a lidar mission I did this past week I will test it for horizontal/vertical this coming week . I first noticed that my checkshots beside the base are off vertically but as much as 1-2 feet. The results of the Base unit are spot with the surveyor when i submit it to OPUS. But the Rover is terrible when comparing known elevation points. I plan to do a point to point comparison between the Rover and TS this week.

I have a buddy who was having the same problem but he stopped logging at 2 min per gcp and started doing only 15 seconds and he felt this improved things due to the Emlid algorithm. But I changed the time in the CSV from 2 minutes to 15 seconds for this same survey and it did not have any effect.

There is something wrong and I hope it can be figured out.

Details of this job:

Surveyor Control: TN State Plane, US-SF
1,371957.019,798978.943,264.37,OPUS/BASE 1,DOLLAR GENERAL
2,373817.6827,799468.2526,300.81,BASE 2,CEMETARY
3,371638.0464,800350.2026,258.73,BASE 3,WAVERLY FARMS & BAMSLEY CV.
4,375454.0418,800556.9131,280.63,BASE 4,RALEIGH-MILLINGTON & KIING STATION
5,374887.0183,801997.9506,271.32,BASE 5,PLEASANT RIDGE & KIING STATION
6,372095.5676,801463.1656,248.88,BASE 6,COLUMBIA WOODS CV.

RS2+ Base: Antenna Height is 1.68 meters (to bottom of antenna). Using a prism pole so height to bottom of antenna is printed height of 1.8m less 0.12 meters.

RS2_ Rover: Antenna Height is 1.88 meters. Prism pole printed height of 2m less 0.12 meters.

The RS2+ Base occupied Control 1 established by the Surveyor. The Orthometric height is 264.37 feet.

I also put a GCP beside the benchmark (about 1.3’). That point was observed twice as gcp7 and gcp8. The PPK Height of GCP7 is 265.466’ and GCP8 is 265.486.

That is a difference of 1.116’

The lidar point cloud is within 1/10 of a foot elevation of all Surveyor control points without any adjustments.

The surveyor BASE 4 was occupied by my GCP3.
BASE 4 Elevation: 280.63’
GCP 3 Elevation: 281.814’
Difference of 1.214 ’


The Surveyor BASE 6 was occupied by my GCP12
BASE 6 Elevation: 248.88’
GCP12 Elevation: 250.102
Difference of 1.222’


Below is the comparison of the Lidar point cloud to the Rover points. They show that there is an approximate 1.2’ error between a 2’ diameter average and the GCP.


Emlid Studio Process screen shots

I used the Orthometric Height of 264.37 (80.58 meters) plus geoid height -27.339 meters =
Ellipsoid Height for the Base unit 53.24 meters

Base pole on left, Rover pole on right (.12 offset on both poles)

The Base coordinates used are the NAD83(2011) coordinates because the set control is in NAD83(2011).

@polina.volkova There were two errors :frowning: The base height was set to 1.88 instead of 1.68. Also the rover height must include the offset so it should have been 2.014 instead of 1.88. So those two errors combined had a 1’ error. Even though I had reworked it many times and checked the details, I overlooked those errors. Sorry for trouble. So this is more in line with what it should be. After reviewing my own post image by image I realized what happened.

I still plan to do a TS to RS2 comparison over 10-20 shots comparing the capture of 2 min vs 15 seconds and see if the results vary. Have a great day.


Hi Tim,

Thank you for sharing the solution! Glad to know you’ve found out the reason.