This document discusses orthographic projection techniques, specifically first angle and third angle projection. It begins by defining projection and multi-view drawings. Orthographic projection produces views with parallel lines perpendicular to projection planes. First angle projection shows the object in front of the vertical plane, with the top view below the front view. Third angle projection shows the object behind the vertical plane, with the top view above the front view. Examples of first and third angle projections are provided to illustrate the different view orientations.

1. Gandhinagar Institute
Of Technology
Engineering Graphics (2110013)
Topic name:-Orthographic Projection
(1st and 3nd angle projection)
Presented By:- (1) jani parth(56)
(2) gothi dhairya(52)
(3) jerin sibi(57)

2. • What Is A Projection?
Any Kind Of Representation Of An Object On A Paper
Screen Or Similar Surface By Drawing Or By Photog-
raphy Is Called The Projection Of That Object.
If Different Straight Lines Are Drawn From The Various Poi-
Nts On The Contour Of An Object To Meet A Plane, The Fig-
uRe,thus,formed By Joining These Points In Correct Seque-
nce Is Called The Projection Of That Object.

3. PROJECTION
ORTHOGRAPHIC
MULTI VIEW
PROJECTION
FIRST ANGLE
PROJECTION
THIRD
ANGLE
PROJECTION
FOURTH
ANGLE
PROJECTION
SECOND
ANGLE
PROJECTION
PICTORIAL

5. What Is Multi-view?
A Multi-view Drawing Is Means Of Representing A Three-
dimensional Object In Two Dimension.

6. What Is Orthographic Projection?
The Term Orthographic Is Derived From The Word ‘ Orthos ’ Which Means
Perpendicular.
The Projection Or View Obtained On A Plane Of Projection When The Proj-
ectiors Are Parallel To Each Other But Perpendicular To The Plane Of Proj-
ection,is Known As Orthographic Projection.
The Orthographic Projection Is A Parallel Projection In Which The Project-
ors Are Parallel To Each Other And Perpendicular To The Plane Of Project-
ion.

7. Orthographic Projection Technique Can Produce Either Single Pictorial Drawing That
Show All The Three Dimensions In One View,or Malti-view That How Only Two Dime-
Nsions Of The
Object In Each View.
(A) In Front Of The Plane Of Projection.

8. (B) Behind The Planes Of Projection

9. Four quadrants
If The Horizontal And Vertical Planes Of Projection Are Assumed To Exte-
Nd Beyond The Line Of Interaction , The Four Dihedral Are Formed Which
Are Designed As First , Second Third And Fourth Angles Or Fourth Angles
Or Fourth Quuadreants.
The Position Of The Object Placed In Any One Of The Quadrant Is Descry-
Bed Below:-
(1) in first quadrant – above h.p. and infront of v.p.
(2) in second quadrant – above h.p. and behind of v.p.
(3) in third quadrant – below h.p. and behind v.p.
(4) in fourth quadrant – below h.p. and infort of v.p.

10. Vertical,horizontal and profile planes

11. Principal planes

12. Rotation Of Planes:-
When The Projection Of An Object Have Been Made On The Various
Planes , They Are Brought Together On A Single Sheet Of Paper By
Rotating The Planes.
The Standard Practice Of Rotation Of Planes Is To Keep The V.P. Fixed
And To Rotate H.P. And P.P. Away From From The Olbject So That They
May Come In Line With V.P.

13. Four quadrant

15. How To Get The Orthographic Projection?
In Order To Obtain An Orthographic Projection Of An Object Proceed As Follow :-
Suppose That The Plane Of Projection( Transparent Plane ) Is Assumed To Be Sit-
Uated In Front Of The Object (In Fig).
If The Imaginary Lines , Called Projectors Are Drawn To The Transparent Plane From
The Various Point On The Contour Of The Object , The Shaped Figure , Thus Formed
By Joining The Different Points In Correct Sequence Will Give The Projection Of The
Front Surface Of The Object In The True Shape And Proportion
Front Surface Projection Which Represents Only Two Dimensions Of The Object
Viz., The Length And Height

16. Since This Single This View Does Not Show The Breadth Of The Object So One Or More
Additional Projection Are Necessary To Complete Its Description.
In General ,Two Projections Are Usually Sufficient To Describe The Simple Object , But
Some Time However , Three Or More Projection Are Required For Complicated Objects.
Important Note:-
In Case Of Orthographic Projection, Either Imaginary Lines Should Be Considered Which
Should Be Mutually Parallel And Perpendicular To Plane Of Projection Or The Observer
Should Look At The Object From An Infinite Distance So That The Rays Of Sight From
His Eyes Become Mutually Parallel To Each Other And Perpendicular To The Plane Of
Projection.

17. Types Of Orthographic Projection:-
The Following Two Type Of Of Orthographic Projection Are Used In
Engineering Practice:-

18. First Angle Projection
In First Angle Projection , The Object Is Considered To Lie In The First
Angle, I.E., In Front Of The V.P. And Above The H.P. Observer Who Is
Theoretically At Infinite Distance Looks At The Object From The Front.
The View Obtained On The V.P. Is Similar To The Front Fae Of The Object
And Is Know As Front View.
Front View Shows Only The Length Of The Object .It Does Not Indicate The
Width.

19. First Angle Projection (Six View)
In The Same Object Is Ossumed To Be Situate In A Transparent Box In
Which The Object Itself Appears To Be Suspended In Air.
Then, The Required Projection Of Aal The Six Respective Planes Of The
Object On The Sheet Of Paper Can Be Drawn By Unfolding The Various
Planes.

21. Features Of First Angle Projection
1.The object lies in the first angle,i.e.,in front of
the V.P and above the H.P.
2.The object lies between the observer and the plane
of projection.
3.Top view is drawn below the front view.
4.Left-hand side view is drawn to the right side of the
front view.
5.Right-hand side view is drawn to the left side of the
front view.

22. EX.1. (FIRST ANGLE PROJECTION METHOD)

23. (front view)
(top view)

24. ( RIGHT HAND SIDE VIEW )

25. EX.2. (FIRST ANGLE PROJECTION METHOD)

26. (front view)
(top view)

27. ( RIGHT HAND SIDE VIEW )

28. EX.3. (FIRST ANGLE PROJECTION METHOD)

29. EX.4. (FIRST ANGLE PROJECTION METHOD)

30. Third angle projection
in third angle projection , the object is considered to lie in the
third angle i.e., behind the v.p. and below the h.p.
the observer who is theoretically at infinite distance looks at the
object from the front.
the rays of sight are parallel to each other and perpendicular to
v.p it may be noted that the front view shows only the lengh and
height of the object.
it does not indicate the width.

31. SIX VIEWS OF THIRD ANGLE
if the same above object is assumed to be situated in a
transparent-box in which the object itself appears to be
suspended in air, then the required projections or image
of all the sixrespective planes on sheet or paper can be
drawn by unfolding the various planes .

32. SIX VIEWS OF THIRD ANGLE

33. Note:this Method Has An Important Dvantage That The
Features Of Adjacent View Are In-just A Position ( Or
Placed Nearer In Actual Contact ), Thus It Is Easier Than
The First Angle Projection In Projecting One View From
The Other When Drawing : and Also Easier In Assigning
These Features When Dimensioning Or Reading The
Drawing.
It Is, Therefore ,Nowadays Coming For General use.

34. Features of third angle projection
1.the object lines in the third angle, i.e., in behind of the v.p. and below
the h.p
2.the object lines between the observer and object
3.top view is drawn above the front view.
4.left-hand side view is drawn to the left side of the front view
5.right-hand side view is drawn to the right side of the front view

35. EX.1. (third ANGLE PROJECTION METHOD)

37. EX.2. (third ANGLE PROJECTION METHOD)

39. EX.3. (third ANGLE PROJECTION METHOD)

40. First angle projection method Third angle projection method
The object is assumed to be situated in
The first quadrant
The object line in between the observer
And the planes projection
View from above (top view) is drawn
below of front view
View from below (bottom view ) is
drawn above of front view
The object is assumed to be situated in
the third quadrant
The plane of projection line in between
the observer and the object.
View from above (top view) is drawn
above of front view
View from below ( bottom view ) is drawn
below of front view.
1
2
3
4
1
2
3
4

41. Symbols of first angle and third angle projection
(1) frustum of a cone

42. Symbol of the first angle projection
Symbol of the third angle projection