Theory
This method is used when
1. The distance between the point and the instrument station is either positive or large or can not be measured accurately due to some field condition as in case or mountainous country.
2. To fill up details.
3. Locating distance and inaccessible objects.
4. Locating the broken boundaries as in case of inverse etc.
Diagram
Procedure
The procedure was as follows
1. The two stations P and Q were selected in such a way that the points to bellocated on paper were easily area from them.
2. The line PQ was plotted center line.
3. From station P rays were drawn for A, B etc.
4. The table was shifted to station Q and after proper orientation took rays for station A, B etc.
5. The intersection of rays from station P and Q had given points a, b etc. on paper as showing in fig.
6. For checking accuracy of work the distance AB on ground was measured and compaired it with its corresponding length ab on paper.
