Land Surveyor Forum

Replies

• 

  srirama.vattamwar October 8, 2012 at 9:24am

  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
• 

  Ken Shipley October 7, 2012 at 3:46am

  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!
• 

  Richard John Hooper October 5, 2012 at 2:33am

  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.
• 

  Leopoldo jr September 27, 2012 at 5:52am

  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..
• 

  Paul Quagge September 26, 2012 at 4:48pm

  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
• 

  Keith A Stephenson September 26, 2012 at 3:51pm

  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

  JORGE ERNESTO CLAVIJO September 26, 2012 at 1:37pm

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

  srirama.vattamwar September 26, 2012 at 7:55am

  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.
• 

  srirama.vattamwar September 26, 2012 at 7:46am

  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

  Tom Arneson September 26, 2012 at 5:15am

  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?