Hi all,
I got an unexpected behavior and a poor performance measuring the elevation of points in a partially covered area (a roadside with North-South direction and mostly steep rocks on the West side... ok, not that simple...), using Catalyst Precise Service (Catalyst 1) on DA2 with Penmap.
Trying to get as much accuracy as possible in such a difficult condition, I stationed on some points in a partially open area. About 20-25 satellites from different constellations were available but mostly concentrated in the right emicycle of the skyplot. RTX solution was used.
During a first session, I was not able to get positions inside the highest quality limits (Penmap quality cursor in right position) despite a long occupation, so I resolved to accept less accuracy and registered some single measurements after lowering the slider by 1 step (2D rms between 5 cm and 1 meter) paying attention that the real time accuracy on the screen were very close to 3-4 cm horizontal and 6-8 cm in elevation, assuming that the final accuracy of the vertical component would be not worse than 10 cm.
After some days I got back to same place in a different time window and I was able to get fixing on the same points under the better quality limits (cursor in the far right position again). I used "averaging" as survey method, logging 10 epochs (in some cases it took more than 10 seconds and some measures were rejected). The exported rms values were very similar to those of the first session, with 2D rms always under 3 cm and 3D rms a bit better than in the previous session.
The unexpected result is that, while 2D coordinates are very similar between the two surveys (difference in the range of 2-3 cm), the elevations have changed about 80 cm (!) in all the surveyed points.
The same set up has been used in both surveys (equipment, antenna height, project file...). Just a setting was changed, that should be irrelevant: a geoid model was applied in the second occupation, whereas probably not used in the first session because not properly downloaded from the cloud. The hellipsoidal heights show the same difference of 80 cm observed on the elevations...
What might have happened? Do you have any idea, suggestion?
Thank you and best regards
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Massimo Gelmini, Gexcel
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