Reconnaissance Survey and Index Sketch in Chain Surveying

Reconnaissance is defined as the process of primary investigation of the land area to be surveyed. It is called a reconnaissance survey or reconnoitres. In this process, the surveyor walks through the whole area and bring remarks on the following:

  1. Obstacles in the area
  2. Determine whether the chosen stations are intervisible
  3. Stations selected must enclose the whole area
  4. Triangles formed are well-conditioned
  5. Note the locations of various objects in the area
Index Sketch


Index Sketch in Chain Survey

The final report of the reconnaissance survey conducted is brought on a neat hand sketch called as the index sketch or the key plan. It is generally a skeleton plan of the survey work conducted primarily.

An Index sketch shows the:
  1. Main Survey Stations
  2. Sub-Stations
  3. Tie Stations
  4. Base lIne
  5. Arrangement of the framework of the triangles
  6. Positions of Objects (Approximate)
Index sketch is an important document held by the surveyor and the one who plots the map. An Index sketch is placed on the first page of the Field Book.

Also Read: What is Chain Surveying - Principles & Features

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