PROJECTION OF POINTS CLASS NOTES FOR ENGINEERING
PROJECTION OF POINTS
CLASS NOTES FOR ENGINEERING
Projection of a point is the most basic. A
point can lie in any of the four quadrants
It shows the location of a light or a fan
point in a building drawing. Two points
when join forms a line. For a point, ‘A’
mark front view with small alphabet
with a dash, ‘a’ ‘. Mark Top view
by a small alphabet without a dash as ‘a’.
Fig. Four quadrants
Horizontal plane (HP) 1-2-3-4 and 1-4-5-6
Vertical Plane (VP) 1-4-8-7 and 1-4-9-10
First quadrant 1-7-8-4-3-2-1
Second quadrant 4-7-8-1-6-5-4
Third quadrant 4-9-10-1-6-5-4
Fourth quadrant 1-2-3-4–9-10-1
Fig. Projections of a point ‘A’ in four quadrants
Key position of points in the quadrants and their projections.
A.
Quadrant |
Position |
front view |
top view |
1st |
In front of VP and above HP |
lies Above x y |
Below x y |
2nd |
Above HP and behind VP |
Above x y |
lies Above x y |
3rd |
Behind VP and below HP |
Lies Below x y |
Above x y |
4th |
Below HP and in front of VP |
Below x y |
Lies Below x y |
| Quadrant | Position | Front view | Top view |
| 1st | (i) lies in HP and distance x in front of VP
(ii) Lies in VP and distance x above HP |
(i) Lies in XY
(ii) Above XY |
(i) Below XY
(ii) In XY |
| 2nd | (i) Lies in HP and distance x behind VP
(ii) Lies in VP and distance x above HP |
(i)Lies in XY
(ii) Above XY |
(i) Above XY
(ii) Lies in XY |
| 3rd | (i) Lies in VP and distance y below HP
(ii) Lies in HP and at distance x behind VP |
(i) Below XY
(ii) Lies in XY |
(i) Lies in XY
(ii) Above XY |
| 4th | (i) Lies in VP and at distance y below HP
(ii) Lies in HP and distance x in front of VP |
(i) Below XY
(ii) Lies in XY |
(i) Lies in XY
(ii) Above XY |
Key features projection of points.
A.
(i) Distance of the front view is always from the HP.
(ii) Top view distance is always from the VP.
-
If distance is above HP, front view is above x y and vice versa.
-
If point is in front of VP, top view is below x y and vice versa.
Representation of front view and top view of a point
A.
(i) Mark front view by a small alphabet with a dash. For example, the front view of point H is h’.
(ii) Mark Top view by a small alphabet without a dash. The front view of point H will be h.
-
Mark Point by a capital alphabet as H.
Q. Types of projections mostly used in engineering drawing.
A.
Projections are orthographic and isometric. Use Orthographic projections. Use HP, VP and PP planes for orthographic projections. Projections on a plane are 2- dimensional.
Different methods of projections in use
A.
First and third angle projections are in common use.
First Angle Projection |
Third Angle Projection |
Object lies in the first quadrant. |
Here the object lies in the third quadrant. |
When object is in between the observer and the vertical plane. |
Vertical plane is in between the observer and the object. |
Front view is on the back, |
In this, front view is on the front, |
Right side view is on left and so on. |
right side view is on right and so on |
https://www.mesubjects.net/wp-admin/post.php?post=7270&action=edit Orthographic Projections
https://www.mesubjects.net/wp-admin/post.php?post=3785&action=edit Q. ANS. Projections