Procedure of Field Work - Chain Surveying, Surveying and Levelling | Surveying and Levelling Notes- Agricultural Engg - Agricultural Engineering PDF Download

8. PROCEDURE OF FIELD WORK

Field work of chain survey should be carried out  according to the following steps:

1.Reconnaissance

Before starting survey work, the surveyor should walk over the whole area to be surveyed in order to examine the ground and determine the possible arrangement of framework of survey. During this investigation, he should examine the intervisibility of the main survey stations. He should ensure that the whole area is enclosed by main survey lines, and also that it is possible to form well-conditioned triangles. He should observe various objects and boundary lines carefully and select the survey lines in such a manner that the objects can be located by short offsets. The base line should preferably be taken through the centre of the area and on fairly level ground.

2.Index sketch

After preliminary inspection of the area, the surveyor should prepare a neat hand sketch showing the arrangement of the framework and approximate position of the objects. He should note the names of the stations on the sketch maintaining  some order (clockwise or anticlockwise). The field work should be executed according to this index sketch. The names and sequence of chain lines should be followed as directed in the index sketch. The ‘base line’ should be clearly indicated in the index sketch.

3. Marking the stations on the ground

After reconnaissance, the stations are marked on the ground by wooden pegs. These pegs are generally 2.5 cm square and 15 cm long, and have pointed ends. They are driven into the ground firmly, and there should be a height of 2.5 cm above the ground. The station point is marked with a cross so that it can be traced if the wooden peg is removed by somebody

4. Reference sketches

To take precautions against station pegs being removed or missed, a reference sketch should be made for all main stations. It is nothing but a hand sketch of the station showing at least two measurements from some permanent objects. A third measurement may also be taken

5.Taking measurements of survey lines and noting them in the field book

Ranging and chaining is started from the base line, which should be measured carefully. The magnetic bearings of the base line are measured by prismatic compass. These measurements are noted in the field book showing the offsets to the left or right according to their position. Then the other survey lines are ranged and chained maintaining the sequence of the traverse. The offsets and other field records are noted simultaneously. The check lines and tie lines are also measured and noted at the proper place. The station marks are preserved carefully until field work is completed.