PROJECTION OF POINTS

PROJECTION OF POINTS 

  1. Which are the types of projections used in engineering drawing?

A.

Orthographic projections are done on HP, VP and PP planes. Since projections are done on a plane, these projections are 2 dimensional.

  1. Describe the position of points in the various quadrants and its projections with respect to the reference line xy.

A.

Quadrant Position Position of front view Position of top view
1st In front of VP and above HP Above xy Below xy
2nd Behind VP and above HP Above xy Above xy
3rd Behind VP and below HP Below xy Above xy
4th In front of VP and below HP Below xy Below xy

Q. Discuss some key features about the projection of points.

A.

(i) Distance of the front view is always from the HP.

(ii) Top view distance of the  is always from the VP.

  • If distance is above HP, front view is above xy and vice versa.
  • If point is in front of VP, top view is below xy and vice versa.

Q.How are the projections of a point marked for its front view and top view?

A.

(i) Front view is marked by a small alphabet with a dash. The front view of point H will be h’.

(ii) Top view is marked by a small alphabet without a dash. The front view of point H will be h.

  • Point as such is written by a capital alphabet.

 

Q.Differentiate between first and third angle projections.

A.

First Angle Projection Third Angle Projection
Object lies in the first quadrant. Object lies in the third quadrant.
Object is in between the observer and the vertical plane. Vertical plane is in between the observer and the object.
Front view on the back, Front view on the front,
Right side view is on left and so on. right side view is on right and so on