Orthographic projection | First Angle and Third Angle Projection systems

Orthographic projection:

A common method of representing three-dimensional objects, usually by three two-dimensional drawings in each of which the object is viewed along parallel lines that are perpendicular to the plane of the drawings.

For example: An orthographic projection of a house typically consists of a top view,plan, and a front view and one side view (front and side elevations).

Difference b/t First Angle &Third Angle Projection

First Angle Projection	Third Angle Projection
The Object is imagined to be in the First Quadrant.		The Object is imagined to be in the Third Quadrant.
The object is lies between the observer and the plane of projection.		The plane is lies between the observer and the Object.
The plane of projection is assumed to be non-transparent.		The plane of projection is assumed to be transparent.
When view are drawn in their relative position. Top view comes Below Front view. Right side drown to the Left side.		When view are drawn in their relative position. Top view comes Above Front view. Right side drown to the Right side.