Simple Problem (Back Ray Method)
This method is extremely useful while one of the plotted stations in accessible from the station to be plotted. The process of resection after orientation through back ray is given below:
(a) Base line O1 O2 is chosen on ground as distance among two well described points O1 and O2 on ground whose positions are measured and plotted accurately on the plan map.
(b) Set the level and orient table at O1. Alidade is placed along O1 O2 such in which signal at O2 is bisected. Along with alidade at O1 another station O3 is sighted, that is needed to be located, draw a line O1 O3, station O3 is marked on map along that ray around.
(c) Shift the table and set it afresh at O3 and orient it through backsight on O1.
(d) Place alidade at O2 on map, sight O2 on ground and draw the ray O2 O3. A point of intersection of rays O1 O3 and O2 O3 will provide or locate the position of O3 on map.
This procedure is repeated to acquire positions of all instrument stations O4, O5 . . . etc. on map.