Theory

The shortest distance between two points is known as the straight lines. When top views of two endpoints of a straight line are joined, the result is the top view of the straight line. Similarly, when the front view of the two end points of the straight line are joined, the result is the front view of the straight line.

Notations & Definition

1. True length - It is Denoted by capital letters. Eg. PQ = 20mm, then the true length of the line is 20mm.

2. Top View length - it is denoted by small letters. Eg. pq = 15 mm, then the top view length of the line is 15mm.

3. Front View length - it is denoted by small letters followed by dash (‘). Eg. pq = 14 mm, then the front view length of the line is 14mm.

4. Inclination of the true length of line with Horizontal plane (HP) - It is denoted by theeta (Q). Eg. If inclination of line with ground or HP is provided as 30 degrees. From this we can infer that theeta = 30 degrees.

5. Inclination of the true length of line with Vertical plane (VP) - It is denoted by fie (Q). Eg. If inclination of line with VP is provided as 45 degrees. From this we can infer that fie = 45 degrees.

6. Inclination of top view length with XY axis - It is denoted by beeta (b). Eg. If inclination of the top view of the line with XY axis is provided as 25 degrees. From this we can infer that beeta = 25 degrees.

7. Inclination of front view length with XY axis - It is denoted by alpha (a). Eg. If inclination of the front view of the line with XY axis is provided as 35 degrees. From this we can infer that alpha = 35 degrees.

Fig.1 Notations

Different Positions of Straight Line

The position of a straight line may also be described with respect to the two reference planes. It may be:

1. Parallel to one or both the planes.
2. Contained by one or both the planes.
3. Perpendicular to one of the planes.
4. Inclined to one plane and parallel to the other.
5. Inclined to both the planes.
6. Projections of lines inclined to both the planes.
7. Line contained by a plane perpendicular to both the reference planes.
8. True length of a straight line and its inclinations with the reference planes.
9. Traces of a line.
10. Methods of determining traces of a line.
11. Traces of a line, the projections of which are perpendicular to the XY axis.
12. Positions of traces of a line.