Extra Care in Fixing New Control Points

                                  Locating point C w.r.t. points A and B

In the given figure, by measuring sides, angles or setting perpendiculars shows the different methods of fixing point C with respect to already fixed points A and B. For fixing new control points (stations) at least two independent processes with respect to already fixed points should be followed. Apart from the minimum measurements needed as shown in given figure, one more measurement should be taken If A &B are already located control points and with respect to them new control point C is to be located. Measuring the lengths of check lines and tie lines will serve this purpose also .

                                 Check line and tie line