Linear referencing system terms

Geospatial

Anchor point

A zero-dimensional location that can be uniquely identified in the real world in such a way that its position can be determined and recovered in the field. Each anchor point has a location description attribute, which provides the information necessary for determining the anchor point's position. Forms of location descriptions can be quantitative, descriptive or both.

Anchor section

A continuous, directed, non-branching linear feature connecting two anchor points, whose real-world length can be determined in the field. Anchor sections are directed by specifying a "from" anchor point and a "to" anchor point. Anchor sections have a distance attribute that is the length of the anchor section measured on the ground. Values are expressed in units of linear distance measure.

Business logic

The business logic tier is composed of a set of Java classes and stored procedures that implement the major functions of the LRS. These procedures include the code that performs linear transformations, linear overlay and staging functions.

Cartesian representation

Cartesian representation A set of lines that can be mapped to a linear datum. The set of lines can be either fully or partially connected. That is, the set can consist of groups that are externally unconnected but internally connected. Cartographic representations have a source attribute that denotes the source (scale and lineage) of the object. Scale values are expressed as rations or as equations relating distances measured on the source form of the cartographic representation to distances measured on the ground. Cartographic representations provide coordinate references; the basis for to-scale visualization of other components of the LRS model; and linkages to extended topological, vector-based GIS data models.

Event

A phenomenon that occurs along a traversal, and is described in terms of its attributes in the extended database. Events can be zero-dimensional (i.e., point) or one-dimensional (i.e., have a linear extent).

Linear datum

A system of procedures for determining and retaining a set of locations along linear features. The system includes linear referencing method(s); and procedures and workflows for storing, maintaining and retrieving location information about parts of the system.

Linear referencing system (LRS)

A system of procedures for determining and retaining a set of locations along linear features.
The system includes linear referencing method(s); and procedures and workflows for storing, maintaining, and retrieving location information about parts of the system.

Linear referencing method (LRM)

A technique used to identify a specific point along a linear feature (e.g., milepoint).

Linear feature

Linear feature A model of a physical (real-world) feature that represents some part of a transportation system, and is organized in such a way that locations along it can be described as a linear expression of some known starting point along its length.

Offset

A location that is described from some known location along a route by evaluating a linear function. Offsets are usually described from the start of the route or from some reference post along a route.

Route

The name given to a logical component of a system of linear features that has some significance for collecting, maintaining and describing locations. An interstate such as I-35 is an example of a route in a highway network.

Route segment

A part of a route that can be represented as a record in a database table. A route is composed of one or more route segments organized in a logical sequence.