Top view is created in third angle projection

General
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top view is created in third angle projection.

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LectureNotes said top view is created in third angle projection.

Answer:
Certainly, let’s delve into the specifics of third-angle projection, particularly focusing on how the top view is created in this system. Third-angle projection is the standard method used primarily in the United States and other countries following the ANSI standards. It is one of the two predominant projection methods used in technical and engineering drawings, the other being first-angle projection.

Third-Angle Projection Explained:

  1. Definition and Basics:

    • In third-angle projection, the object is considered to be placed inside a transparent box.
    • The views are projected on each face of this imaginary box. Subsequently, the box is unfolded to lay flat, revealing the standard projection views.

  2. View Placement:

    • Top View: In third-angle projection, the top view (or plan view) is placed above the front view on the drawing sheet.
    • Front View: The front view is the main view and is typically placed at the center.
    • Right Side View: The right side view appears to the right of the front view.

Creating the Top View:

  1. Position of the Object:

    • Imagine the object inside the transparent box. In third-angle projection, views are created by projecting the features of the object onto the surrounding planes of the box.

  2. Projecting to the Top:

    • For the top view, you need to look at the object from directly above.
    • The object’s silhouette as seen from above is projected downwards onto the horizontal plane at the top of the box.

  3. Unfolding the Box:

    • When you “unfold” or “flatten” the box, the projection on the top face of the box is placed above the front view on the drawing sheet.

Illustration:

Imagine a simple cube to visualize the projection process:

  • Front View: The front face of the cube.
  • Top View: The face of the cube you would see if you were looking straight down onto it.
\begin{array}{rl} & \text{Top View} \\ & +-------------------+ \\ & \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \frontarrow{Downward Projection}\ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \text{Front View} \\ & +-------------------+ \\ \end{array}

Summary of Third-Angle Projection:

  • The top view provides a clear perspective from above, aiding in understanding the overall layout and relative positioning of features.
  • Third-angle projection is essential for clarity, particularly in complex engineering and architectural drawings.

Final Answer:
In the third-angle projection, the top view is accurately created by projecting the object’s features downward onto a plane, then placing this view above the front view on the drawing sheet. This method is widely used due to its logical and intuitive arrangement of views.