FrancisH, post: 382711, member: 10211 wrote: Not sure if this applies to your neck of the woods, but here in Singapore, both sides of the road are occupied by high rises. When I say 'high', I really mean HIGH. Most of the time, even static would give out float solutions. Nevermind about RTK radio signals. So what we do is to locate some traverse stations in parks/open rest areas along the road and hope that GPS signals are ok.
FrancisH, Thanks for the information. Been to Singapore in 1967 (RR from Vietnam) so I now understand your problem.
Hope all is going well for you.
JOHN NOLTON
Today was a good example. We are monitoring a very large structure where new underground mining (blasting) is happening nearby. We did two obs in November, 1 in December, 1 in January, 1 in March, and one last week. The obs last week show a 1 cm movement of the two main stations on the structure (not apparent in previous surveys). There are a bunch of secondary points, but they all depend on the two main points. I went back today to check, and the angle today agreed with the angle last week by 0.4" (289 m and 158 m sights to very carefully centered tripods). This is a jump of about 10" in the angle from the previous epochs. I am still analyzing to determine if those points (and the whole structure) moved or if the reference station moved (which is off structure). I have data from multiple GPS receivers and a 1"/1 mmå±1 ppm total station to analyze. The structure weighs about 2.5 million tons (1.25 million tons of concrete).
We recently installed two new stations off structure, but last week was the first epoch for those. Future surveys will use those as well, but unfortunately we don't have prior data, as those would tell me a lot more.
If you consider pre GPS, pre EDM, and you had to determine a position by resection, from points 20-50K feet, or more, away, you'd need a true subsecond angle.
With a 1" second T2, the procedure is a bit more than 2 D/R sets. But manageable, like 16 sets, or more. The rules of statistics apply. A 5" gun takes more work, but not impossible.
And 1" angles were measured before 1" instruments were available.
