Dear Colleagues,
We want to establish new Bench Marks (BM) on the basis of existing one. We are using TOPCON HIPPER-II GPS device. Kindly guide me in this regard.
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Dear Sir Azam
new file attached my recomendation for urban planning is please go with total station .if you want accuracy you have old point data like E,N,Elevation then you shift 5 to 10 times your bench mark depends on sight clearence..please search on google for how to use total station you will get many useful material i am now working on topcon 239n
Hi Lalith,
Very interesting. In southern California we are lucky if we get a small aluminum sign right at the BM. Many are destroyed every year but we surveyors do are best to perpetuate the elevations when we come accross them and send our data to the appropriate agency.
We have to do precise levelling establish Fundamantle Benchmarks and procceed if we want to establish a network for a country onnectet to Mean sea level.
But just for local topographic survey establish BMs by levels locally and go ahead.
Agree with Lalith,
For a control network, precise leveling loops. For a small site or just to perpetuate a BM elevation, closed level loop or MTA with a total station is sufficient.
What methods and tools one uses depends on what order of precision is to be achieved and the size of the project.
Stil fundamantle Bench Marks established in 1800 could be seen and secured
hear in Sri Lanka.We can see fenced area giving a warning not to do any blasting around 50m area.
Dear all thanks a lot for providing very helpful guidance.
Dear it is very simple.
Before starting your job you should have at least three known control points in project area.
You have to select suitable places for BM.
Take static observation on these BMs (time span as per leg distance).
Static observation is very common for surveyors.
Download your static data and process on TBC.
your hipper II can be used for bench marking because it is accurate in RTK.i have seen its data sheet now. i think you can understand with this diagram i made for you
Dear Amir sahib,
I had seen your diagram but i need the starting point to work i.e what are the considerations and procedures to achieve max. accuracy.
If you are trying to establish vertical control off of an existing benchmark and hope to achieve 3rd order or better results, using a total station or level and performing a closed level loop from and to the benchmark is standard practice. You can adjust the newly established elevations based on your error of closure, if any.
Even with the newest, latest and greatest RTK equipment, there is elevation error which cannot be substantiated without running a level to check the RTK elevations. Even post-processed static GPS data will see vertical error.
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