1. 1 EDM Calculations ASM 215 EDM CALCULATIONS

2. 2 EDM Calculations HORIZONTAL DISTANCE MEASUREMENT n In plane surveying, the distance between two points means the horizontal distance. n If the points are at different elevations, then the distance is the horizontal length between plumb lines at the points. n When using an EDM device, corrections to a horizontal distance still need to be made.

3. 3 EDM Calculations REDUCTION OF EDM SLOPE DISTANCE TO HORIZONTAL

4. 4 EDM Calculations DIFFERENCE IN ELEVATION (MEASURING DOWN HILL) n Assume that the difference in instrument height is negligible

5. 5 EDM Calculations DIFFERENCE IN ELEVATION (MEASURING UP HILL) n Assume that the difference in instrument height is negligible

6. 6 EDM Calculations SLOPE ANGLE (MEASURING DOWN HILL) H = L cos  n Assume that the difference in instrument height is negligible

7. 7 EDM Calculations SLOPE ANGLE (MEASURING UP HILL) H = L cos  n Assume that the difference in instrument height is negligible

8. 8 EDM Calculations CORRECTION FOR VERTICAL OFFSET

9. 9 EDM Calculations SLOPE ANGLE (MEASURING DOWN HILL) H = L cos  n Assume that the vertical offset between the theodolite and the EDMI is negligible

10. 10 EDM Calculations SLOPE ANGLE (MEASURING UP HILL) H = L cos  n Assume that the vertical offset between the theodolite and the EDMI is negligible