Overview[ edit ] Comparison of several types of graphical projectionincluding elevation and plan views To render each such picture, a ray of sight also called a projection line, projection ray or line of sight towards the object is chosen, which determines on the object various points of interest for instance, the points that are visible when looking at the object along the ray of sight ; those points of interest are mapped by an orthographic projection to points on some geometric plane called a projection plane or image plane that is perpendicular to the ray of sight, thereby creating a 2D representation of the 3D object. Customarily, two rays of sight are chosen for each of the three axes of the object's coordinate system; that is, parallel to each axis, the object may be viewed in one of 2 opposite directions, making for a total of 6 orthographic projections or "views" of the object: The left and right views, which are known as elevations because they often show the features along the "vertical" length of an object such as a building.
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. Principles Of Surveying First Angle Projection In this, the object is assumed to be positioned in the first quadrant and is shown in figure.
The object is assumed to be positioned in between the projection planes and the observer. The views are obtained by projecting the images on the respective planes.
Note that the right-hand side view is projected on the plane placed at the left of the object. After projecting on to the respective planes, the bottom plane and left plane is unfolded on to the front view plane.
The bottom plane is unfolded towards the bottom to obtain the Top view below the Front view and aligned with the Front View. Third Angle Projection —.3 The Sun declination angle, δ, has the range: – ° angle is important in navigation and astronomy.
For most solar design purposes, however, an approximation accurate to within about 1 degree is adequate. Third Angle VS First Angle Description: Both third angle and first angle projection display the standard three orthographic views of a part or assembly.
The key difference between third angle and first angle is the layout of the part on the sheet. Third Angle projection is a method of orthographic projection which is a technique in portraying a 3D design using a series of 2D views. An alternative method to Third Angle Projection is First Angle Projection.
Different countries and regions typically use one method or the other although this can depend on a company's customer. In First Angle Projection we place our object in the First Quadrant (see above figure).
Orthographic Projection is a way of drawing an 3D object from different directions. Usually a front, side and plan view are drawn so that a person looking at the drawing can see all the important sides. Third Angle VS First Angle Description: Both third angle and first angle projection display the standard three orthographic views of a part or assembly. The key difference between third angle and first angle is the layout of the part on the sheet. regardbouddhiste.com: XCSOURCE Right Angle 90 degree Vertical Horizontal Laser Line Projection Square Level Laser Square BI Home Improvement.
This means that the Vertical Plane is behind the object and the Horizontal Plane is underneath the object. In Third Angle Projection the Object is placed in the Third Quadrant.
regardbouddhiste.com: Elite Screens ezFrame, " , Sound Transparent AcousticProP3 Fixed Frame Projection Projector Screen, RWH1-AP3: Home Audio & Theater.
regardbouddhiste.com: XCSOURCE Right Angle 90 degree Vertical Horizontal Laser Line Projection Square Level Laser Square BI Home Improvement.