Explain ‘Intersection Method’ of plane table surveying with neat sketch. Also give situation when intersection method is used.
1 Answer
1. Lay out a base line AB and measure it and Plot a distance ‘ab’ on sheet using any scale.
2.Set up instrument at ‘A’ with ‘a’ over ‘A’
3.Orient the table by placing alidade ‘ab’ and turn table until ranging rod at ‘B’ is bisected and clamp it.
4. With alidade touching point ‘a’ draw rays 1, 2,3,4,5 of indefinite length as shown in figure below.
5. The table is then moved to station ‘B’ orient by back sighting on ‘A’. Draw rays towards points previously sighted i.e. 6,7,8,9 rays are drawn to determine points intersection, d, g, f, c.
Situation when used:
1. Locating details of area.
2. For locating distant and inaccessible points, broken boundaries, bank of river etc.
3. For plotting position of points to be used subsequently as the instrument station.
4. It is suitable when it is difficult or impossible to measure distance as in the case of the survey of mountainous country.
5. The only linear measurement required is that of a base line.