Surveying and leveling Procedure

Leveling Procedure

After the instrument has been leveled, a staff rod reading i.e back sight reading is taken on Bench mark and height of instrument is computed from this reading.

Take as you want the intermediate sight (I.S.) readings and note it to the field book.A Turning point is necessary when, it is difficult to sight the reading with the same 

set of instrument. Before the Turning point (T.P.) the Take the Foresight (F.S.) reading. Foresight reading is very important in the surveying and leveling.The instrument

is carried to a new position along the line,re leveled, and Take your first Back sight reading after setting the dumpy level.It will provide you new H.I. Additional I.S. can be taken 

along the line and process is continued until the survey is closed.

Determination of Elevation:

The elevation of point is determined by subtracting its rod reading from height of instrument. Suppose your elevation of the Bench mark is 12. Meter. The Staff reading at this point is 1.68 m.

The relative rod reading of other place is 1.85. So determine the elevation of this place is 

                        B.M. = 12 M

                        B.S. = 1.68 m

                        F.S. = 1.88 m

                        H.I. = B.M. + B.S.

                        H.I. = 12 + 1.68 = 13.68 m

            So 

                        Elevation = H.I. - F.S

                                  = 13.68 - 1.85 

                                  = 11.83 m

When the point will be higher, elevation will be higher but rod reading at this point will be lower and vice versa.

Determination of horizontal Distance by stadia Method.

When it is need to measure distance with quick time with accuracy, the stadia method is used. Surveying instrument equipped for stadia measurement have two additional horizontal cross hairs called stadia hairs shown in figure.

They are placed in a position with one below the horizontal leveling cross hair,so that when a leveling rod is held 100 units away from the level, there will be 1.00 unit of staff visible between the top and bottom stadia hairs.

Thus if a metric staff is held 100 meters from the instrument, a difference in vertical interval between the top and bottom stadia hairs will be 1 m. The difference between the rod reading of the top stadia hair and the rod reading of the 

bottom stadia hair is called stadia interval. The distance in meters from the instrument to the rod is equal to the stadia interval multiplied by 100.

For Example (Shown in the figure) The top stadia hair reading is 1.46 and the bottom stadia hair reading is .87. Thus the stadia interval is equal to .59 meter. The distance from the instrument to the rod is equal to .59 multiplied by 100 which gives a distance of 59 meter.