The definition ANGLE is the difference between two straight lines g1 and g2 in a flat plane. A angle will be created at the cross section between the two lines g1 and g2.

The inclination is a specific angle related to the angle a created between the line g3 and a horizontal line g4, whereas the horizontal line g4 lies in the intersection between a vertical plane E2 and the horizontal (reference) plane E1, which must be absolutely horizontal.

With an inclination measuring instrument not only an angle can be detected but also, related on the base length, the heights of a point (topography of a surface) may be defined. This fact and the simple use of an electronic inclination measuring instrument allows the efficient measuring of machine tool guide ways and surfaces.