Method of Perpendiculars

This is another graphical method. It involves the following steps [Ref. below figure].

1. Draw line ae perpendicular to ab. Keep alidade along ea & turn the table until A is sighted. Clamp table and then draw the ray Bb to intersect the ray Aac at e [ref .Fig (a)].

2. When fcC are in a line draw cf perpendicular to bc and clamp the table. Draw Bb to intersect Ccf at F [ref Fig. (b)].

                         (a)                                    (b)                                                      (c)

                           Method of perpendiculars  of solve three point problem

3. Join cf drop bp perpendicular to ef to obtain the plotted position 'p'.

4. Orient the table such that pbB are in a line. Clamp the table to place it in accurate orientation.Resections Aa and Cc can be used to verify the orientation.