Tacheometric method is adopted for contouring of very steep hills.
The steps are as follows:
i) Set up the tacheometer at the top of the steep hill. Tacheometer is a theodolite fitted with stadia diaphragm. The stadia diaphragm has three horizontal parallel hairs instead of one as found in a conventional cross hair diaphragm.
ii) With the help of a tacheometer it is possible to determine the horizontal distance of the point from the telescope as well its vertical level.
iii) The steep hill is surveyed at three levels – the base of the hill, the mid-level of the hill and the top level of the hill.
iv) Using the tacheometer reading are taken all around the hill at equal angular intervals on all these three
levels.
v) The radial plot thus obtained is worked in the office to interpolate points of equal elevation for contour mapping.
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