GALE’S TRAVERSE TABLE:
Traverse computations are usually done in a tabular form, a more common form being Gale’s traverse table. The following computations are made in the Gale’s traverse table.
- Compute reduced bearings (R. B.) from the W. C. B.
- Using measured length of each line and computed R. B., calculate latitude and departure of each line (i.e., calculate consecutive coordinates of each line). Latitude = L = l cosθ, Departure D = l sinθ
- For consecutive coordinates of point B, length of line AB and R.B. of line AB are used and for consecutive coordinates of point C, length of line BC and R.B. of line BC are used.
- Find corrected latitudes and departures. The sum of Northing must be equal to the sum of Southing. The sum of Easting must be equal to the sum of Westing.
- Compute independent co-ordinates from the corrected consecutive co-ordinates. The co-ordinates of first point are assumed. The co-ordinates of first point are assumed in such a way that the independent coordinates of all the points are positive and the whole of the traverse lie in the first quadrant.
- Calculate: Closing Error, Direction of Closing Error and Relative Error of Closure
Example: Prepare Gale’s Traverse Table to adjust the closing error of the closed traverse ABCDA for the following data:
|Gale’s Traverse Table|
Closing Error, Direction of Closing Error and Relative Error of Closure: