## What is difference between 1st and 3rd angle projection?

The object is placed between the observer and projection planes. The plane of projection is taken solid in 1st angle projection….Difference between First Angle Projection and Third Angle Projection :

SR.NO First Angle Projection Third Angle Projection
7 Left view is at the right side of vertical axis. Left view is at the left side of vertical axis.

Why we use only 1st and 3rd angle projection?

We consider that horizontal plane rotates in clockwise direction after having projection on it. that’s why we use 1st angle and 3rd angle projection. because only in this two quadrants we will get the both views after clockwise rotation of horizontal plane.

### Which projection is used in India?

In India, the polyconic projection is commonly used by Survey of India (SOI). All SOI toposheets are in the polyconic projection. Map Scale is the ratio of distances on map to distances to on the surface of the earth. It is specified in verbal, numeric or graphical form on all standard maps.

What do you mean by HT and VT of a line and a plane?

• Horizontal Trace (HT) The real or imaginary line of intersection of a plane. with the HP is called horizontal trace of the plane. HT is always located in the TV. • Vertical Trace (VT) The real or imaginary line of intersection of a plane with. the VP is called vertical trace of the plane.

## What are first and third angle drawings?

The difference between first and third angle projection is in the position of the plan, front and side views. In third angle, what you see from the right would be drawn on the right. In first angle, the view from the right would be projected through and drawn on the left.

What is the symbol of 1st and 3rd angle projection?

The third angle symbol is shown at the top left of Figure 1. The first angle symbol is shown at the top left of Figure 2. Each symbol represents the views of a cone from that angle view. Both third and first angle symbols show the circular top view of a cone and the right view of the cone.

### What is difference between isometric and orthographic?

Isometric: a method of representing three-dimensional objects on a flat surface by means of a drawing that shows three planes of the object. Orthographic: a method for representing a three-dimensional object by means of several views from various planes.