Leveling: closed loop and double way run
I need some help because I do not have much experience in high precision leveling.
The leveling will be carry out by a Topcon DL-101C, 2 invar rods with bipods and standard base plates. They demanded us for a high precision leveling ( 2.5 mm√L) for monitoring some buidings maybe involved by a landslide. We have only one control BM (elev.=0 m.) outside the area involved by the landslide.
What do you think about adopting a closed loop and a "double way run" (starting from a BM and turning back on it after a number of turning points) together? I have attached an image to illustrate more the possible plan:
1) from BM1 up to point 2 and turning back to BM1 (Magenta).
2) Closed loop from point 2 (green)
3) from 6 to 9 and turning back to 6 (red)
4) from 14 to 16 and turning back to 14 (light blue)
In the image red points are fixed into the pavement or walls, blue points would be the positions of the base plates (frog). We need more base plates positions because the area is quite steep and the specs do not want more than 40 m. between the rod and the turning point. Orange area are buildings and black area are unaccessible/occlusive.
Thanks a lot.
P.S....Why can't I attach files?
Your picture does come up if I click on the little box. Maybe it's the way Dropbox works that the picture won't embed?
I think it's because you're new Can't post images or links right away
This is a good read I would worry as much about procedure as closure.
As mvanhank222 alluded to above, PRODEDURE is actually more important than "closure" alone.
IF you use recognized [documented] procedures specifically designed for your stated [precision] goals, then your closure SHOULD be within your tolerance goal. If it isn't, then you have an observation/calculation/etc. problem that needs to be addressed. Sometimes you will just have to do it again.
In any case, you WILL have to use the same PROCEDURES each and every time you re-run your line[s] to verify what (if any) movement there may be in the study area.
Just by 2-bits