The detection and classification of the straightness of guide rails can be subdivided according to different detection methods. For general guide rails, the straightness of guide rails is usually measured using a level and a bridge plate using the pitch method. The straightness error of the guide rail is determined based on an error curve that approximates the actual line of the guide rail obtained.

In the measurement of high-precision guide rail straightness, the straightness level of the guide rail itself will be on the same order of magnitude as the straightness level of the detection tool. At this time, the pitch method cannot separate the straightness errors of the guide rail and the tool. In this case, a high-precision measurement method or technique without a reference is needed to effectively separate the errors, commonly known as the "straightedge reversal measurement error separation method".

The current common methods for detecting the straightness of guide rails are classified as follows:

1. Benchmark measurement: Compare the measured line with the selected standard line

2. No benchmark measurement: taking a certain amount of test points on the measured surface and processing the measurement data using a certain method