Overview
ISO 19148:2021 - Geographic information - Linear referencing specifies a conceptual schema for expressing locations relative to a one‑dimensional object by measurement along that object and, optionally, offset from it. The standard defines data structures and operations required to implement linear referencing systems (LRS), linearly located events and linear segmentation. Examples and most explanatory material draw from the transportation domain, but the standard is applicable to utilities, environmental protection, location‑based services and other sectors that define locations relative to linear objects.
Key topics and requirements
- Conceptual schema: a formal model describing Linear Referencing System components, value and distance expressions, referents, and linear elements.
- Linear elements and referents: definitions and semantics for the one‑dimensional objects used as baselines for measurements.
- Position expressions and distances: mechanisms for expressing a location by measure along a linear element, including handling of directionality and broken‑chainage.
- Offsets and cross‑sectional positioning (XSP): support for lateral and vertical offsets, offset vectors and cross‑sectional conventions.
- Linearly located events and segmentation: modelling events located on a line, event times, and linear segment sets for analysis and visualization.
- Conformance and testing: conformance classes (data types and operations) and an abstract test suite to verify implementations.
- Interoperability considerations: harmonization with other ISO/TC 211 geographic information standards and annexes with examples, application schema, and backwards compatibility notes.
Practical applications
ISO 19148:2021 is designed to support real‑world spatial workflows that require precise location referencing along linear infrastructure:
- Transportation asset management (mileposts, roadworks, incident reporting)
- Utilities network management (pipeline segments, cable routing)
- Environmental monitoring along rivers or corridors
- Location‑based services that reference routes, trails or transit lines
- GIS software and data model design for linear feature analysis