Basics of Coordinate Metrology
Unit 4:  Geometric Elements - Line (in space)

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The first standard geometric element is the line. A line has the following characteristics:
infinite extension along the line
direction given by the line

A straight line is determined by at least two points. It is described by a point P (x,y,z) and a direction vector .

The point p is described by a local vector. A local vector or vector is an arrow pointing from the origin of the coordinate system (zero point) to the point P (x,y,z). The local vector is defined by the number triple (x,y,z) of the coordinates of the point P.

The direction vector or briefly vector is an arrow pointing along the line. It is defined by the number triple V (x,y,z).

 

Tip: The direct measurement of straight lines usually has a high measuring uncertainty. A more stable solution is to calculate a straight line as the intersection of other standard geometric elements.
For the example in figure at bottom right, it is better to measure the two adjacent planes, instead of probing the part edge directly, and to calculate the edge as the intersection of these two planes.

       

Element:
Line
Display:

Parameters:
point P (x, y, z), 
direction vector V (x, y, z)
Required minimum number of probing points:
2 probing points
Example using a part:
(Edge of a part)