First angle projection is a method or angle of orthographic projection and in this method, 3D drawings are created in 2D. In the first angle projection object is kept in the first quadrant and lies between the plane of projection and observer.
The first angle projection is approved internationally except the United States and in this projection, the object is placed above the horizontal plane in the first quadrant and is positioned in front of the vertical plane.
By placing it in the first quadrant of dihedral or first octant of a trihedral angle this view of an object should be taken and this system is called the first angle system. The non-transparent plane of projection is to be assumed.
The planes are straightened by rotation by taking a top view on the horizontal plane & front view on the frontal plane and side view on the profile plane and in this wayside view comes beside the front view and the front view comes over the top view.
Symbol of First Angle Projection is;
Views In First Angle Projection:
There are three main views in the first angle projection such as;
The Side View:
The right side or left side is the standard view of multi-view drawings and the depth and the height dimensions are shown in the side view. To the side of the object plane of projection is parallel.
Object right and left side views are projected on the vertical right and vertical left plane to draw left and right side views
By looking to the object from the left side or right side this view is prepared and in this view breadth and height of an object is shown.
The Front View:
By drawing perpendiculars from all points on the edges of the part to the plane of projection a front view of projection is obtained and the plane of projection upon which the front view is projected is known as a frontal plane.
As projections are drawn such a plane that is placed in front of an object is called the frontal plane.
These views are prepared by placing the object in front and in this view the height and length of the object are shown. To draw the front view the object is projected on the vertical and horizontal planes respectively and the horizontal plane is rotated clockwise direction according to the rule of projection.
The Plane View:
This view is seen directly from above and it is also called a bird eye view just like looking from top to the object.
By looking at the object from the upper side this view is prepared and in this view length and breadth of an object are shown.
To draw the front view the object is projected on the vertical and horizontal planes respectively and the horizontal plane is rotated clockwise direction according to the rule of projection.
Characteristics of First Angle Projection:
There are the following characteristics of first angle projection as given below:
Over the top view front view always comes.
Under the front view top view always comes.
To the left at the front view right side view always comes.
To the right of the front view left side view always comes.
To the observer the view is always in the opposite direction.
To the view and observer the object is always in the middle.
Important Points Of First Angle Projection:
There are following important points in the first angle projection such as;
In the first quadrant the object is kept.
Between observer and plane of projection object lies.