Aquaculture Engineering (2+1)

Obstacle to chaining but not ranging 2

Unit 1- Surveying

Chain surveying

Obstacle to chaining and ranging

Obstacle to chaining but not ranging

When it is not possible to chain round the obstacle

I Method

Select point B on one side and A and C on the other side(Fig(a)). Erect AD and CE as perpendiculars to AB and range B, D and E in one line. Measure AC, AD and CE. If a line DF is drawn parallel to AB, cutting CE in F perpendicularly, then triangles ABD and FDE will be similar.

II Method

Erect a perpendicular AC and bisect it at D (Fig(b)). Erect perpendicular CE at C and range E in line with BD. Measure CE. Then AB = CE