How to Drop a perpendicular to a given chain Line from a Point Outside

 

    How to Drop a perpendicular to a given chain Line from a Point Outside

 

If the chaining work is progress and an offset point is situated outside from chain line. There are two type of question.

1.     When the point is Accessible

2.     When the point is Inaccessible.

           

1.     When the point is Accessible:-

In the above picture AB is a chain line and C is an offset point. C is a point from where a perpendicular to do draw on chain line AB.

With C as centre and any convenient length of tape as radius. Make an arc EF on the chain line AB .Fix the arrows on the cutting point on the AB. Bisect the length EF .D is the bisect point . CD line will require perpendicular.

In the above picture, the length EF is 142.52 mt. After bisection the points EF . Measure

the 71.26 mt from E TO F line and mark the point D .Point D will be perpendicular CD

on the line chain line AB.

2. When the point inaccessible :-

Let C be the inaccessible point. Choose the suitable point D and E on the line AB. Set

out the perpendicular line FD and EG from the line CE and CD. Mark  the intersection 

point H . The line CI is required perpendicular.