Land Surveyor Community Forum

Hi guys, 

These days I am using Top-con Total Station. That top-con software has some thing called " Grid Factor".

I am using SLD 99 Sri Lanka coordinate system and used GPS to establish few control points at site.

My problems are   

  1. Should I care Grid Factor when doing large scale surveying and setting out?
  2. What is the real idea of Grid Factor ?
  3. Why this grid factor setting not in Sokkia instruments?

I found this information from top-con manual.

Calculation Formula 

1) Elevation Factor

Elevation Factor =                         R       : The average radius of the earth
                           R+ELEV.          ELEV.    : The elevation above mean sea level

2) Scale Factor

Scale Factor : Scale Factor at the surveying station

3) Grid Factor

Grid Factor = Elevation Factor × Scale Factor

Distance Calculation

1) Grid Distance

HDg = HD × Grid Factor       HDg : Grid distance    HD : Ground distance

2) Ground Distance

      HD = HDg

            Grid Factor 

Welcome any idea and Thanks for helping 

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  • Please let me know how could I know the scale factor of surveying station 

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