CE101
Engineering Drawing
Lec3: Orthographic
Projections
Indian Institute of Technology
Guwahati
,In engineering drawing, the word ‘projection’ means
• an image or the act of obtaining the image of an object.
• Technical people often refer to the image as a view.
Projection System
1. Observer or stationary point
2. Object
3. Projectors
4. Plane of projections (POP)
,PROJECTION METHOD
Depending on the relationship between the projectors and POP, and the number of POPs
used for the projections, the projection methods are classified as follows
, View comparison
Type Advantage Disadvantage
Multi-view drawing Accurately presents Require training
object’s details, i.e. to visualization.
size and shape.
Pictorial drawing Easy to visualize. Shape and angle distortion
Circular hole
becomes ellipse
Right angle becomes
obtuse angle.
Perspective drawing Object looks more Difficult to create
like what our eyes Size and shape
perceive. distortion
Distorted
width
Engineering Drawing
Lec3: Orthographic
Projections
Indian Institute of Technology
Guwahati
,In engineering drawing, the word ‘projection’ means
• an image or the act of obtaining the image of an object.
• Technical people often refer to the image as a view.
Projection System
1. Observer or stationary point
2. Object
3. Projectors
4. Plane of projections (POP)
,PROJECTION METHOD
Depending on the relationship between the projectors and POP, and the number of POPs
used for the projections, the projection methods are classified as follows
, View comparison
Type Advantage Disadvantage
Multi-view drawing Accurately presents Require training
object’s details, i.e. to visualization.
size and shape.
Pictorial drawing Easy to visualize. Shape and angle distortion
Circular hole
becomes ellipse
Right angle becomes
obtuse angle.
Perspective drawing Object looks more Difficult to create
like what our eyes Size and shape
perceive. distortion
Distorted
width
