Direct Methods

It consists in finding vertical and horizontal both controls of the points which lie on the selected contour line. Commonly Instrument is used for vertical control levelling. After taking fly levels a level is set on a commanding position in the area from the nearby bench mark. Plane of collimation/height of instrument is found and for a contour line is calculated the required staffs reading. The instrument man asks staff man to move up and down in the area until the required staff reading is found. By using his instruments A surveyor establishes the horizontal control of that point. Man directs the staff man to another point after that instrument where the same staff reading may be found. By establishing horizontal control it is followed. Thus on a contour line several points are established on one or two contours lines and properly noted down. Ideally Plane table survey is suited for this work. The instrument is shifted to another point to cover more area after required points are established from the instrument setting. At the same time the level and survey instrument need not be shifted. It is better if both are nearby so as to easily communicate. Sometimes hand level and Abney levels are also used for getting speed in levelling. This method is tedious, slow but accurate. It is appropriate for small areas.