In the case of hilly area tachometric contouring method is used. Here the instrument known as tachometer which is a theodolite utilised which is determine horizontal distance and elevation of the point.
As shown in fig tachometry set up at a point approximately at centre of area. Radial line are set making angle with either the magnetic meridian or with the 1st radial line. On each radial line staff reading
Are observed at different points. When reading along all the radial line have been observed. It is then plotted on a sheet to a suitable scale.