# Difference Between First Angle And Third Angle Projection Pdf

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- First Angle And Third Angle Projection
- Orthographic Projection
- What is first angle orthographic projection?

## First Angle And Third Angle Projection

In technical drawing and computer graphics , a multiview projection is a technique of illustration by which a standardized series of orthographic two-dimensional pictures are constructed to represent the form of a three-dimensional object. Up to six pictures of an object are produced called primary views , with each projection plane parallel to one of the coordinate axes of the object. The views are positioned relative to each other according to either of two schemes: first-angle or third-angle projection. In each, the appearances of views may be thought of as being projected onto planes that form a six-sided box around the object. Although six different sides can be drawn, usually three views of a drawing give enough information to make a three-dimensional object.

Every engineer must know how to read engineering drawings and the most integral part of this is knowing the difference between first and third angle projection. A collection of 2D drawings can be used to represent a 3D object in orthographic projection and consists of six orthographic views Top, Bottom, Right, Left, Front and Back view also known as six principle views. Out of these six, front, right side and top view are the most commonly used ones. But how do you get these orthographic views from a 3D object? We essentially have two main types of projection techniques, the First angle projection, and the Third angle projection. Both of them do the same job, but there are differences in the way we get the results. Divide the plane into four quadrants.

First of all, we know that the first angle projection system and third angle projection system both are the methods used for orthographic projection drawing. In the first angle projection system, the object placed in the first quadrant and in third angle projection system the object placed in the third quadrant. If one regards the artesian coordinates as being made of quadrants, then 1st angle and 3rd angle are two different quadrants in which an object is places and different planes on to which the drawing is projected. In 1st angle, the object is between the observer and the plane of projection. In 3rd angle, the plane is between the observer and the object. Also Read: Types of Screwdrivers. In this, the object is assumed to be positioned in the first quadrant and is shown in figure.

## Orthographic Projection

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. First Angle Projection : In the first angle projection, the object is placed in the 1st quadrant.

## What is first angle orthographic projection?

Third Angle projection is a method of orthographic projection which is a technique in portraying a 3D design using a series of 2D views. It is positioned below and behind the viewing planes, the planes are transparent, and each view is pulled onto the plane closest to it. The front plane of projection is seen to be between the observer and the object. The images below show the projection of the object on a 3D box surrounding the object.

First angle projection and Third angle projection are two different methods of creating a 2D drawing of a 3D part. First Angle Projection is commonly used in all countries other than United States. It is mainly used in Europe and Asia countries. Following table describes what is the difference between or comparison between First Angle Projection vs Third Angle projection.

To represent a 3D object in a 2D plane orthographic projection system is used. Orthographic projection systems utilizes parallel lines, to project 3D object views onto a 2D plane. In this system, objects can be placed in the first or third quadrants. Second and fourth quadrant are not used because of their limitations. Click this link!!

*Collection of 2D drawings which enables you to have a complete representation of an object is called orthographic projection. Collection of 2D drawings consist of six orthographic views Top, Bottom, Right, Left, Front and Back view also called as six principle views.*

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