Dear All,

Please could any one suggest the best possible way to close the traverse with least error.

we have used Prism over Tribatch but still could not Achive the Good Result.

The total Length of Travese is 5Kms, and we have 9 Intermediate Stations.We have tried with four Different Makes of Total Stations 

The least we could Achive was +130mm Error in Easting and +95mm Error in Northing and 90 mm in Elevation.

Thanking  You,

Srirama.Vattamwar

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  • Dear All,

    Thank you for the valuable Information and suggestions we could finally close this job. The client satisfied with the latest result. In the latest Job we have taken closer stations, max distance between station was 280mts and the weather was nice and cool, We have changed the tribatch as well.

    At closing we got +26mm E and +34mm N and the elevation was 105mm. So we have used an 28X sOKKIA AUTOLEVEL to close the Vertical Error and we ended with 15mm. 

    Once again Thank you all for giving me your valuable time and needful information.

    Thanks & Regards,

    Srirama. Vattamwar

  • I agree with Keith and Leopoldo - Unadjusted tribrachs, incorrect prism constants, and loose tripods are often overlooked as a source of error. Good luck with this puzzle!

  • Hi Srirama,

    Does your traverse have large differentials in elevations?

    Some years ago I ran a traverse from a trig beacon to a previously coordinated traverse station near a road in hilly terrain.  The difference in elevation between begin and end point I cannot recall, but it was substantial - a couple of hundred meters.

    In South Africa we generally apply a scale enlargement and sea level (elevation) correction to each of the traverse leg distance readings, the factors being determined by meaning the Easting coordinates and elevation for the entire distance of the traverse.

    In this instance I found the mis-closure was pretty bad, but after puzzling it out I decided to apply separate sea level corrections to each traverse leg based on the elevations of each traverse station pair.  This worked out very well and I got a very good closure.

  • Hello Srirama,

    make sure that your tribrach is calibrated, check your prism constant and take backsights and foresights in 3 readings to take the final mean horizontal reading.

    for elevation you must run a levelling and use double set up method.

    use "starnet" to compute both traverse and level

    hope it helps..

  • Hello Srirama,

     

    Still thinking about your survey...in the mean time you could refer to this:

     

    Surveying Measurement and Their Analysis by R.B.Buckner

    ISBN-10: 0910845115 | ISBN-13: 9780910845113

     
    Is there a big temperature and pressure difference throughout the day?
     
    Where specifically is your survey?
     
    Are you keeping your forsights and backsights relatively the same?
    Are you keeping forsights and backsights as long as possible?
     
    Still Thinking, Paul
  • Make sure your tribracs are in adjustment. Do not break your setup but move the instrument into the foresight tribrac, Double your angles turn direct and reverse. Be sure your EDM in the gun is adjusted and also your vertical angle.

  • Land Surveyor

    Dear Syrama: use 3 tribrach , read 2 faces, and use umbrella. 

  • Dear scotte D. Warner,

     

    Thank you for responding my query,Here are the details of the Job.

    We have considered azimuth coordinates

    station Code(starting Point) A1: Easting: 10,000, Northing:20,000 Elevation: 100 mts

    Instrument Used: Pentax set 3030R

    Accuracy of the Instrument: 3"

    Date Instrument Calibrated recently: 13/09/2012 

    Time duration to close the traverse: 8 Hours

    Temperature: Min: 30 degree Celsius,Max 33 Degree Celsius

    Reflector Used: Prism.( Prism was placed on Tribatch at each station), for taking back site only the top part of tribatch and upper portion of Total station leaving the base plate on tripod was moved.

     

    Total Intermitent Stations: 13 Stations ( minimum distance between each station was 300mts and the maximum was 620 mts (only between two stations).

     

    Closing co-ordinates: Easting:10000.131, Northing:19999.905, Elevation:99.819.

     

    Topography: Plain.

     

     

    Thanks & Regards

     

    Srirama Vattamwar

     

    Scott D. Warner, R.L.S. said:

    A misclosure in this scenario would be about 1 : 32,000.  Is that really so bad?  Adjust your error of closure proportionally to the length of each segment and I think you have done well.  Or you could use the least squares method, or several others, but I do not see a problem with your precision.  Any heat waves? Error is inherent in every measurement.  In my opinion, as a surveyor, you should concentrate less on the math and more on the task at hand, unless you are bound by contract or law to achieve a precision in position of better than 1 : 32,000 and need to prove it in some sort of way.

  • Dear Paul,

    Thank you for responding my query,Here are the details of the Job.

    We have considered azimuth coordinates

    station Code(starting Point) A1: Easting: 10,000, Northing:20,000 Elevation: 100 mts

    Instrument Used: Pentax set 3030R

    Accuracy of the Instrument: 3"

    Date Instrument Calibrated recently: 13/09/2012 

    Time duration to close the traverse: 8 Hours

    Temperature: Min: 30 degree Celsius,Max 33 Degree Celsius

    Reflector Used: Prism.( Prism was placed on Tribatch at each station), for taking back site only the top part of tribatch and upper portion of Total station leaving the base plate on tripod was moved.

    Total Intermitent Stations: 13 Stations ( minimum distance between each station was 300mts and the maximum was 620 mts (only between two stations).

    Closing co-ordinates: Easting:10000.131, Northing:19999.905, Elevation:99.819.

    Topography: Plain.

     

    Thanks & Regards

    Srirama Vattamwar

     



    Paul Quagge said:

    Hello Srirama,

     

    Without any negativity, can you please provide your step by step process and describe the topography?

     

    Thanks, Paul

  • GeoEducator

    This could be a scale problem or a problem with the beginning or ending control points. What is the coordinate grid system? Are you applying grid and elevation scale factors? How were the beginning and closing points established? How good is the beginning azimuth or direction control?

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