First Angle Projection Vs Third Angle Projection

first angle projection vs third angle projection

First angle projection and third angle projection are the vocabularies of technical drawings. These are the latest standards used in engineering drawings to communicate design intent among different stockholders. Let’s learn more about 1st angle projection and 3rd angle projection in this article.

It’s very common for beginners who just passed out of colleges to get confused between first angle projection vs third angle projection. In fact its a matter of confusion among experienced engineers also. In simple words, 1st angle projection and 3rd angle projection are the types of Orthographic Projection system which is used to project three-dimension objects into two-dimensional projection view.

Must Read: What Is Orthographic Projection

Orthographic projection works on the principle of projecting views to imaginary planes which is called reference planes. In 2D drafting, you can have two planes perpendicular to each other and normal to the human eye. One plane is in the X- Direction and other is in Y Direction. These two reference planes, when placed at the perpendicular, creates four-quadrant where you can place a 3D object to project views.

First Angle Projection Vs Third Angle Projection

What Is First Angle Projection

In the first angle projection, the object is placed in the 1st quadrant. The object is positioned at the front of a vertical plane and top of the horizontal plane. First angle projection is widely used in India and European countries.

In the first angle projection, the object is placed between the observer and projection planes. The plane of projection is taken solid in 1st angle projection.

first angle projection vs third angle projection

What Is Third Angle Projection

In the third angle projection, the object is placed in the third quadrant. The object is placed behind the vertical planes and bottom of the horizontal plane. Third angle projection is widely used in the United States.

In the third angle projection, the projection planes come between the object and observer. The plane of projection is taken as transparent in 3rd angle projection.

first angle projection vs third angle projection

Difference between first angle projection vs third angle projection

We all might know that in Orthographic Projection there are mainly six views ( Front, Back, Top, Bottom, Right, Left). Out of these six views, three views ( Front, Top, Right) are important and most of the drawing usually have these three views.

First angle projection and third angle projection can be broadly differentiate based on a couple of criteria as mentioned below.

Object Placement

In the first angle projection, the object is placed between the object and projection planes. In third angle projection, the object is placed behind the projection planes.

Projection Plane Placement

In the first angle projection, the projection planes are at the behind and bottom of the object. In the case of third angle projection, projection planes are front and top of the object.

Symbol

When you look at a drawing, for a moment you may not diagnose whether its a first angle projection or a third angle projection. The only way to figure it out is by looking at the projection symbol. It’s a mandatory requirement for drawing to have a projection symbol.

first angle projection vs third angle projection

View Placement


The view Placement differs in 1st angle projection and 3rd angle projection due to the different position of projection planes. But before that, we should know the rule of Orthographic Projection 
The Orthographic Projection states that you have to virtually rotate the horizontal plane clockwise to project the views in a 2D drawing.


In first angle projection,  the front view is placed above the unfolded line and the top view is placed below. The right side view is placed on the left side of the front view. The left side view is placed on the right side.

1st angle projection vs 3rd angle projection
First Angle Projection


In third angle projection, the front view is placed below the unfolded line and the top view is placed above. The right side view is placed on the right side and the left side view is placed on the left of the front view.

first angle projection vs third angle projection
Third Angle Projection

Snippet Of 1st Angle Projection Vs 3rd Angle Projection

First Angle PrpjectionThird Angle Projection
Objects are placed in 1st QuadrantObjects are placed in the third quadrant
Projecion planes comes behind the objectProjection planes shows up front of object
Plane of projection is non transparentTransparent plane of projection
Front view is at the top of the horizontal axisFront view at the bottom of the horizontal axis
Top view at the bottom of the horizontal axisTop view at the top of horizontal axis
Right view is at the left side of vertical axisRight view is at the right side of vertical axis
Left view is at the right side of vertical axisLeft view is at the left side of vertical asxis
Preffered choice in India and asian countriesWidely used in United State and Australia

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Conclusion

To sum up, first angle projection and third projection are just two types of orthographic projection types which are widely used to create a two-dimensional drawing. These are standard that every company follows so that they don’t face any issues in communicating the design intent across the globe.

If you have any question regarding first angle projection vs third angle projection, then do ask in the comment section and I will be happy to respond. Also if you do feel that I missed something to add here, you can raise that in the comment section.

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Frequently Asked Questions

What Is First Angle Projection?

First angle projection is a type of projection where the object is placed in the 1st quadrant and projection views are drawn accordingly

What Is Third Angle Projection

Third angle projection is a type of projection where the object is placed in the 3rd quadrant and projection views are drawn accordingly

Where does First angle projection and Third angle projection get used?

First angle projection is used in India and other Asian countries whereas third angle projection is widely used in the United States and Australia

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