The orthographic projection system is used to represent a 3D object in a 2D plane. The orthographic projection system utilizes parallel lines, to project 3D object views onto a 2D plane. According to the rule of orthographic projection. To draw a projection view of a 3D object on a 2D Plane. The horizontal plane is rotated in the clockwise direction.

Types of Orthographic projection systems are first angle and third angle projection.

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

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

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**Difference between First Angle Projection and Third Angle Projection :**

SR.NO | First Angle Projection | Third Angle Projection |
---|---|---|

1 | The object is placed in the first quadrant. | The object is placed in the third quadrant. |

2 | The object is placed between the plane of projection and observer. | The plane of projection is placed between the object and observer. |

3 | The plane of projection is opaque. | The plane of projection is transparent. |

4 | Front view is at the top of the horizontal axis. | Front view at the bottom of the horizontal axis. |

5 | Top view at the bottom of the horizontal axis. | Top view at the top of horizontal axis. |

6 | Right view is at the left side of vertical axis. | Right view is at the right side of vertical axis. |

7 | Left view is at the right side of vertical axis. | Left view is at the left side of vertical axis. |

8 | It is widely used in Europe, India, Canada. | It is widely used in United State and Australia. |