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Homework Help: Surveying (Geomatics) involving allowable misclosures

  1. Oct 19, 2012 #1
    1. The problem statement, all variables and given/known data
    Compute the following permissible misclosure for the following line of level.
    a 15kilometer loop of third order level.


    2. Relevant equations
    C=msqrt(K)
    where K is the distance and M is a constant


    3. The attempt at a solution
    For the most part I just need to verify if I copied my answer correctly because when I calculate this, I get 46475MM as my answer, but what I have written down is 46.5MM
    I can see the similarity in the answer, off by a factor of 1000, so could anyone please confirm if my answer is correct and the one I have written down from class just has the wrong units? If I did do it wrong, where did I go wrong?

    I plugged in 12 for m since it's a third order level and plugged in 15KM for K, or 15,000,000MM.
     
  2. jcsd
  3. May 28, 2018 #2
    why are surveyors are permitted to have allowable mis close and how they deal with it?
     
  4. Jun 1, 2018 #3

    Baluncore

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    @ Abdul Faiyad. Welcome to PF.
    The survey makes accurate measurements that are affected by many things such as instrument errors, atmospheric refraction, variation of the vertical due to local mass distribution and earth tides. It is only when the survey is closed that the closure error is known. If the error is too big, the survey must be checked or repeated. If the error is acceptable, it can then be partitioned and distributed to the intermediate stations based on the length of the sights between stations.
     
  5. Jun 1, 2018 #4

    Baluncore

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    @ mathnoobie.
    You have not specified what units you are required to use with C = m * Sqrt( k )
    Dimensional analysis requires the units of m to be Sqrt( length ).
    Mixed multipliers will explain a factor of 1000.
    Where should you use metres or mm ?
     
  6. Jun 1, 2018 #5

    Baluncore

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    Numbers are meaningless without units.
    Third Order: Differential levelling. Misclosure in mm is not to exceed 12 * √ km.
    For 15 km you have 12 * √15 = 46.5 mm
     
  7. Jun 1, 2018 #6

    Bystander

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    mathnoobie was last seen:
    Aug 18, 2013:
    Useful information, even for a "necropost."
     
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