Hello,
I would like to share some results with a reach module and a Leica AT 502 antenna in RTK static mode on an already known point. Corrections are received from NTRIP casters.
Positions are logged and then averaged with continuous samples of various sizes, fix only. The maximum error is noted according to averaging time. The time to get a fix varies between 10 and 20 mn.
reference station with GPS + Baidou, baseline 6.5 km, delta height 300 m :
Averaging | Max error (m)
time | Distance height
1 s 0.03 0.10
1 mn 0.03 0.09
30 mn 0.02 0.08
1 h 0.02 0.05
5 h 0.01 0.01
reference station with GPS only, baseline 37 km, delta height 1250 m :
Averaging | Max error (m)
time | Distance height
1 s 0.07 0.44
1 mn 0.03 0.44
30 mn 0.03 0.38
1 h 0.03 0.32
2 h 0.03 0.30
2h20mn 0.02 0.29
Hi Pascal
Some other experiment with dual frequency receiver showed that centimeter true accuracy (100 % of measures) with long baseline is unreal. Specifications of professional grade receivers are misleading. For example, Leica Geosystems claims an accuracy of 5 mm + 2 ppm (EMQ) for their dual frequency receivers. That is 5 + 2 x 6.5 = 18 mm for a 6.5 km baseline.
But what Leica Geosystems call EMQ is a one sigma two dimentional error, which is 39% of measures. So you have to multiply by three to get max error, which is in this case 5 cm.
Regards
Understood. 5 cm is ok for a single point in RT at 6.5 km. In general you record much more than 1 point, and accuracy is then divided by sq(n).
But for this type of range, you know by closing your network or work with several base points that you got better results. That’s why we record long sessions with a lot of observations. It is all about time you are ready to spend on a baselines before having a nice solid and accurate solution. Then, you can use RTK only very locally, let say 1-2 km max from RTK base.
That’s why your first post is interesting. I am curious to know if Emlid wrote a white paper on the subject of trials on baseline lengths / observation times / accuracies obtained.
