Object: To determine the latitude, departure, and coordinates of point/line.
Equipment: Digital theodolite, tripod stand, leveling staff, ranging rods, plum bob, prismatic compass, and tape.
Theory:
The theodolite traverse is not plotted according to angles or bearings. It is plotted by computing the latitude and departure of the points (consecutive coordinates) and then finding the independent coordinates of the points.
The latitude of a line is measured parallel to North-South line and the departure of a line is measured to the East-West line. The latitude and departure is also called Northing and Easting respectively.
Fig: 04.1 Latitude and departure
The combination of easting and northing is called coordinates of a point, it can be written as (Easting, Northing).
Consecutive Coordinates: the latitude and departure of a point calculated with reference to proceeding point are called consecutive coordinate.
Independent coordinates: the coordinates of any point concerning a common origin are said to be independent coordinates.
Procedure:
- Mark station A then mark North with help of prismatic compass at station A.
- Set the instrument at station A and do the temporary adjustment.
- Horizontal clamp is kept fixed and vertical clamp loosened, then set telescope at 90˚ with the help of vertical clamp and vertical screw.
- Now the vertical clamp is tightly fixed and horizontal clamp is loosened and telescope is directed towards north and bisect the ranging rod.
- Horizontal clamp is fixed and set horizontal angle as 0˚ by using reset button.
- Now lose the horizontal clamp and the telescope is directed towards B and bisects the ranging rod at B.
- Note the H.A. displayed on the display screen, which is the bearing of line AB.
- Then measure the distance from station A to B with help of tape and note it in observation table.
- Repeat the above process for bearings and distances of lines BD, DC and CA.
- Find the latitude by using LCosθ and departure by using LSineθ (where L is the distance of the line and θ is the bearing of that line).
- Let the coordinates of point A as (12960.2ft, 85654.98ft).
- And find the coordinates of other stations by adding latitudes and departures in coordinates of station A.
Observations:
Line | Length (ft) | Bearing | Latitude | Departure | Coordinates |
