Help Distributing Error In A Level Survey 

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Dave Walker
Posts: 2

Joined: 8/31/2012
Topic  Help Distributing Error In A Level Survey       Flag »  Reply »
Hello all

I was wondering if there was anyone out there who could help explain how to distribute a misclosure error in a level survey.

I carried out a survey of a road. i used several TBMs and several change points. When i closed the survey i flew back using the same change points and ended back the survey on my original TBM.

My first TBM reduce level value was 10000, my second TBM reduce level value was 9378 and 3rd TBM was 8948.

When I fly back to close the survey I re-survey TBM3 and I got a reduce level of 8948, but when I re-survey TBM 2 I got a reduce level of 9379 (a difference of 1mm from the previous value) and my final TBM value I get a reduce level of 10005 a difference of 5.

How do you distribute the error, I simply do not understand the process of distributing the error. If someone could explain how you would distribute the error then that would help a great deal.

The issue i have is that i do not know over which change points i made the error (assuming that the error was as a result if misreading).

Thanks

Thanks in advance
  Friday, August 31, 2012 at 3:00:38 PM
JOSESC
Posts: 5
Location: Kampala, Uganda

Joined: 8/30/2011
Reply  Re: Help Distributing Error In A Level Survey Flag »  Reply »
If u trust ur TBM levels u should av closed at each TBM and the distribution of correction should av stopped at each TBM using equation below;
     correction per instrument stn = -1*(misclosure at each TBM/NUMBER OF BACK SIGHT up to that TBM)*N where N is the number of back sight.
However if u did not trust ur TBM and u didnot close at each the correction based on ODM should be used and distributed using the equation above.

  Monday, September 24, 2012 at 12:48:39 PM

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