In Engineering survey, various type of surveys such as plane table survey, traverse survey, aerial and photographic surveys etc. are carried out .
Purpose or Aim of engineering survey: To prepare Contour map and Topographical map of the site. The contour interval may be taken as 1 to 3 m for fairly plain area, and 5 to 10 m for hilly area. For Dam site careful triangulation survey is required where contour interval is less than 1 m. Horizontal scale may be 1 in 500 to 1 in 1000.
Necessary information from contour plan: From the contour map of reservoir area, the water spread of the reservoir at any elevation may be directly determined by measuring the area with help of planimeter.
Following information can be obtained from contour map.
1. Water spread area from Area-elevation curve
2. Arrangement of lines of communication.
3. Capacity of reservoir from storage elevation curve.
4. Site for waste weir and outlets.
5. Suitable dam site.
From the contour map, the storage capacity of the reservoir should be fixed by assuming the height of the dam. Then the valuable land and properties which may get submerged in the reservoir can be found out