Projection Methods:

• 1^st & 3^rd Angle System
• 2^nd & 4^th Angle System
• Symbols of 1^st Angle And 2^nd Angle and Guidelines

1^st Angle System:

• It uses Shadow technique.
• Imagining the  Object Placed in 1^st Quadrant.
• Plane of projection is located behind the object.
• Torch is used to produce shadow, that’s why LHSV goes on Right of FV.
• For LHSV, the profile reference plane (PRP) is rotated clockwise around Z axis and for TV, the Horizontal Plane (HP) is rotated clockwise around X axis.

     The orthographic Layout is as shown below:

RHSV	FV	LHSV
	TV

                                                      1. orthographic Layout

3^rd Angle System:

• It uses Mirror/Transparent Approach.
• imagining the Object placed in 3^rd Quadrant.
• Plane of projection is located between object and observer.
• For LHSV, the profile reference plane (PRP) is rotated Anticlockwise around Z axis And for TV, the Horizontal Plane (HP) is rotated clockwise around X axis.                                                                      

        The orthographic Layout is as shown below:

	TV
LHSV	FV	RHSV

                                             2. orthographic Layout

 2nd & 4th Angle System:                                  

Are 2^nd   & 4^th Angle System is Available?

 Answer: Yes. This systems are available. But having some drawbacks so not in use.

• Orientation Problem, leads to miscommunication.
•  In 2nd angle projection system, the plane is in between object and observer.
•  In 4th angle of projection the object is in between the observer and plane. 
• ·If we turn clockwise, Front and top views overlaps.

1^st And 3^rd  Angle Symbols:

Guidelines:

• Object is used to represent symbols is a frustum of cone.
• Smaller size portion of object must be present always on left side.
• Side view should not contain Hidden Lines.

        

 

                                             

1st Angle Method of Projection                                                            3rd Angle Method of Projection  

Example with a 1st angle:

                                                               1st angle method of Projection                                                                                                                                                                                                                                           

Example with a 3rd Angle Method:

                                                                                   

3rd Angle Method of Projection

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