A Linear Referencing System (LRS) is a way of storing geographic data or events by using a relative position along a line. The advantage of this system is the ability to locate a point with one parameter (typically known as measure) instead of two (such as X,Y coordinates). The LRS is used to store reference points for networks of linear features, such as roads, railroads, pipelines, telephone lines, and rivers.

Linear Referencing functions (see LRS-related Functions) operate on data types that include a measure (M).