Projections of Lines : Lecture No 04

1. Unit No:03
Projections of Points & Lines
Yash B. Parikh
M.Tech. (CIM)
Assistant Professor
Department of Mechanical Engineering
Symbiosis Institute of Technology

2. 2
Question 2 : ( Type 2)
A line AB having it’s end A 25 mm above H.P. and 20 mm in front
of V.P. The end B is 85 mm above H.P. and 50 mm in front of
V.P. The projector distance between these ends is equal to 80
mm. Draw the projections of line AB and show it’s T.L. , angle
with H.P. & angle with V.P.
Prof. Yash Parikh

3. 3
Traces of the Line
 When a line is inclined to a reference plane, the point in which
the line meets the reference plane is called it’s trace.
 The trace of a line is defined as a point at which the given line, if
produced, meets or intersects a plane.
Horizontal Trace : (H.T.)
 It’s the point of intersection of a line with H.P.
 It’s denoted by point H, hence in projections by h’ and h.
 The position of H.T. is always given w.r.to the V.P.
Vertical Trace : (V.T.)
 It’s the point of intersection of a line with V.P.
 It’s denoted by point V, hence in projections by v’ and v.
 The position of V.T. is always given w.r.to the H.P.
Prof. Yash Parikh

4. 4
H.T. & V.T. in following Cases
1. Line is parallel to both H.P. & V.P.
2. Line is perpendicular to H.P. & parallel to V.P.
3. Line is perpendicular to V.P. & parallel to H.P.
4. Line is inclined to H.P. & parallel to V.P.
5. Line is inclined to V.P. & parallel to H.P.
Prof. Yash Parikh

5. 5
H.T. & V.T. when line is inclined to both R.P.
 First find out final elevation & plan of the line. (i.e. a’b’ and ab)
Locate H.T. :
 Produce the elevation a’b’ to meet the XY reference line at point
h’.
 Through h’ erect a line perpendicular to XY reference line.
 Now produce plan ab to meet this perpendicular line, the
intersection point is called H.T. & represented by h.
Locate V.T. :
 Produce the plan ab to meet the XY reference line at point v.
 Through v erect a line perpendicular to XY reference line.
 Now produce elevation a’b’ to meet this perpendicular line, the
intersection point is called V.T. & represented by v’.
Prof. Yash Parikh

6. 6
H.T. & V.T. when line is inclined to both R.P.
Note:
1. h’, v’ and final elevation are on the same line and at an angle α
to XY reference line.
2. h, v and final plan are on the same line and at an angle β to XY
reference line.
Prof. Yash Parikh

7. 7
Question No – 03 (Type 03)
A line BC, 80 mm long is inclined at 45˚ to the H.P. &
30˚ to V.P. It’s end B is in the H.P. and 40 mm in
front of V.P. Draw it’s projections & determine it’s
traces.
Prof. Yash Parikh

8. 8
Thank You
Prof. Yash Parikh