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The Canadians know how to set a monument…
I was working in Canada this week, doing a survey in a remote area using Trimble RTX (real time over satellite). Since the RTX system uses ITRF2008, epoch 2005.0, I wanted to make sure that I apply the correct transformation back in the office. I looked up the nearest “High Precision 3D” station on the NRCAN website. Here is the station:
It is near a highway, but you can’t see it from the highway. I didn’t have a tribrach with me, so I had to put the R10 directly on the threaded bolt, which could introduce a small H error, probably within a few mm. There is a metal plate on top of the monument with a 5/8″ threaded rod protruding about 0.1 meters. This is one of their CBN stations (equivalent to our FBN?). If you look down below knee level, there are two metal objects protruding from the monument.
The one on the left is an elevation reference point (benchmark):The one on the right is a metal ring to secure equipment against theft, I assume.
The bolt on top (where the R10 is) and the mark on the side are both first order benchmarks. There are three other first order benchmarks in bedrock within 100 meters or so.
This is probably the best monument I have ever come across. I use a lot of pedestals in my work (deformation surveys), and have two on my property, but none with the side mark and the tie down ring, and they are not quite as massive. And I also like the fact that there are other BM’s nearby to check this one.
On their web page you can select the datum and epoch and it will provide a coordinate. I had the precisions set for 0.05 m H/0.10 m V, and the R10 took about 10 minutes to get below those tolerances. I did a three minute observation (observed control point). Using their published ITRF2008 epoch 2005.0 coordinate, the horizontal difference was 0.009 m, the vertical was 0.08 m. Precisions for the stored point were 0.04 m H and 0.07 m V. The project is somewhat loose, 40 cm accuracy is acceptable on the points surveyed (photo control), but I wanted to get 0.05 m H/0.10 m V just to be safe.
Why can’t we set mons like these???
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