First Angle Projection Vs Third Angle Projection: Key Differences
The use of orthographic projection is the representation of a 3D object on a 2D plane. This projection system makes the utilization of parallel lines for protecting the 3D object views on a 2D plane. According to the orthographic projection rule- one needs to rotate a horizontal plane in the clockwise direction in order to draw a projection view of any 3D object onto a 2D plane.
There are the following types of Orthographic Projection Systems:
First Angle Projection – One can imagine the object to be in the first quadrant.
Third Angle Projection – One can imagine the object to be in the third quadrant.
What is a First Angle Projection?
The First Angle Projection schema imagines the object in the first quadrant. One can place an object on the top of the horizontal plane and at the front of the vertical planes. The first angle projection is utilized mostly in India and various European countries. It places the object between the projection planes and the observer. You can take the plane of projection to be solid in the first angle projection.
What is a Third Angle Projection?
The Third Angle Projection schema imagines the object in the third quadrant. One can place an object on the bottom of the horizontal plane and behind the vertical planes. The first angle projection is utilized mostly in the United States. It places the object between the observer and the object. You can take the plane of projection to be transparent in the third angle projection.
Difference Between First Angle Projection and Third Angle Projection
| Parameter | First Angle Projection | Third Angle Projection |
| Method of Projection | When you divide a plane into four quadrants, you can place any object in the first quadrant in a first angle projection schema. | When you divide a plane into four quadrants, you can place any object in the third quadrant in a third angle projection schema. |
| Placement of Objects | It places the object between the observer and the plane of projection for the first angle projection. | It places the object between the observer and the object for the third angle projection. |
| Sequence of Views | In the first angle projection schema, the views come in the following sequence- top left, then clockwise, the Right view, Front view, and the Top view. | In the third angle projection schema, the top view sits at the top of the front view, and the right view sits on the right side of the front view. |
| State of Projection Plane | You can take the plane of projection to be opaque (solid) in the first angle of projection. | You can take the plane of projection to be transparent in the third angle of projection. |
| Uses | Widely used in India, Europe, Canada. | Widely used in Australia and the United States. |
| Identification | You can identify a drawing of the First Angle Projection by the symbol of the first angle projection. This symbol of the angle of projection typically appears near the Title block in the angle of projection block. | You can identify a drawing of the Third Angle Projection by the symbol of the third angle projection. This symbol of the angle of projection typically appears near the Title block in the angle of projection block. |
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