Distance Bearing Calculation from Coordinates - Sri Lankan Grid (aka Kandawala)
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Umapathy உமாபதி
Sep 27, 2012, 1:03:31 AM9/27/12
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Dear Colleagues,
Traversing the polygon (In case of Hazard Reduction such as Completion or in case of Hazard such as Confirmed Hazardous Area) can be done either coordinates alone from a GPS or DGPS or Compass and measurement. Incase of GPS or DGPS error won't be cumulative (I mean the error reading in one point will not affect the reading of the other point) however practically High Sensitive series GPS (such as Garmin HS series) cannot be purchased in certain countries. Distance and bearing calculation are more accurate for the points which are close proximity. In legacy IMSMA to current IMSMAng we collect both the details (I mean the coordinates as well as the distance and bearing). Accurate bearing can be obtained by theodolite but often times we end up with magnetic compass as they are not only simple to carry but also relatively cheaper than theodolite.
To plot the graph in ArcGIS we may make use of the coordinates in an excel sheet (If you are on 64bit windows need to have 2007 office system drive:Data connectivity components as per the thread XLSX-PROBLEM-Failed-to-Connect-to-Database-Class-Not-Registered) and xtools will do the work.
Coming back to the subject I have developed some formulate to calculate the distance and bearing. Distance is of course easy as it's a pythagorean theorem. Bearing I used combination of Trignometry with bearing from North. Sri Lankan grid (aka Kandawala) uses 1 unit as 1 meter so it's relatively easy to make calculations. MagneticDelination for Sri Lanka is in between 2-3 degrees. Generally 3 is the value used in the field for calculation purposes as Magnetic Compass points to Magnetic North while we need to draw polygon for True North.
Appreciate if some one verify that the formuale is correct. Feel free to post your comments. Thanks in advance.
Please refer the attached excel sheet
Distance calculation:=IF(C3<>"",SQRT((C3-C2)*(C3-C2)+(D3-D2)*(D3-D2)),SQRT((C2-$C$2)*(C2-$C$2)+(D2-$D$2)*(D2-$D$2)))
Bearing Calculation==3+IF(AND((C3-C2)>0,(D3-D2)>0),90-(ATAN((D3-D2)/(C3-C2))/PI())*180,IF(AND((C3-C2)>0,(D3-D2)<0),90-(ATAN((D3-D2)/(C3-C2))/PI())*180,IF(AND((C3-C2)<0,(D3-D2)<0),270-(ATAN((D3-D2)/(C3-C2))/PI())*180,IF(AND((C3-C2)<0,(D3-D2)>0),270-(ATAN((D3-D2)/(C3-C2))/PI())*180))))
Regards
Regunathan Umapathy (Uma)
Traversing the polygon (In case of Hazard Reduction such as Completion or in case of Hazard such as Confirmed Hazardous Area) can be done either coordinates alone from a GPS or DGPS or Compass and measurement. Incase of GPS or DGPS error won't be cumulative (I mean the error reading in one point will not affect the reading of the other point) however practically High Sensitive series GPS (such as Garmin HS series) cannot be purchased in certain countries. Distance and bearing calculation are more accurate for the points which are close proximity. In legacy IMSMA to current IMSMAng we collect both the details (I mean the coordinates as well as the distance and bearing). Accurate bearing can be obtained by theodolite but often times we end up with magnetic compass as they are not only simple to carry but also relatively cheaper than theodolite.
To plot the graph in ArcGIS we may make use of the coordinates in an excel sheet (If you are on 64bit windows need to have 2007 office system drive:Data connectivity components as per the thread XLSX-PROBLEM-Failed-to-Connect-to-Database-Class-Not-Registered) and xtools will do the work.
Coming back to the subject I have developed some formulate to calculate the distance and bearing. Distance is of course easy as it's a pythagorean theorem. Bearing I used combination of Trignometry with bearing from North. Sri Lankan grid (aka Kandawala) uses 1 unit as 1 meter so it's relatively easy to make calculations. MagneticDelination for Sri Lanka is in between 2-3 degrees. Generally 3 is the value used in the field for calculation purposes as Magnetic Compass points to Magnetic North while we need to draw polygon for True North.
Appreciate if some one verify that the formuale is correct. Feel free to post your comments. Thanks in advance.
Please refer the attached excel sheet
Distance calculation:=IF(C3<>"",SQRT((C3-C2)*(C3-C2)+(D3-D2)*(D3-D2)),SQRT((C2-$C$2)*(C2-$C$2)+(D2-$D$2)*(D2-$D$2)))
Bearing Calculation==3+IF(AND((C3-C2)>0,(D3-D2)>0),90-(ATAN((D3-D2)/(C3-C2))/PI())*180,IF(AND((C3-C2)>0,(D3-D2)<0),90-(ATAN((D3-D2)/(C3-C2))/PI())*180,IF(AND((C3-C2)<0,(D3-D2)<0),270-(ATAN((D3-D2)/(C3-C2))/PI())*180,IF(AND((C3-C2)<0,(D3-D2)>0),270-(ATAN((D3-D2)/(C3-C2))/PI())*180))))
Regards
Regunathan Umapathy (Uma)
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