Bench Marks

[ollylandandwater]

I have been asked to provide a method of providing a bench mark AOD on a site, that is about 2 miles from anything that could be used as a level datum and the site is surrounded by undulating terrain and thick woods! Is there an easy way of setting up this bench mark without using a dumpy level / total station to transfer the level over the 2 miles?

 

[IRstuff]

How accurate does the benchmark need to be?

Can you use a differential GPS? With post processing, we've gotten good results for our applications, but we only need to be accurate to about 1 cm

TTFN

Eng-Tips Policies FAQ731-376

 

[ollylandandwater]

IRstuff

10mm should be accurate enough! although i have very little experence with differential gps and post processing, is the kit easy to use? is the kit easy to hire? would the time saved ofset the hire cost, compared doing it the traditional way with a dumpy level?

cheers

olly

 

[IRstuff]

Well, most surveyors that you could hire have DGPS rigs, and they'd do the same postprocessing.

The cost of the hardware is pretty steep, I think we paid something like $10K for the Trimble DGPS and the software for acquiring the correction factors and doing the post processing.

I would think that hiring the surveyor would be the most economical route, particularly if this is a one-time event.

We purchased our hardware because we expected to be doing this sort of thing relatively often and felt that owning the hardware gave us some additional flexibility.



TTFN

Eng-Tips Policies FAQ731-376