Stationing and chainage are two names for the same idea: locating a point on a road, railway or pipeline by its distance along a named alignment from a defined start, plus its offset to the left or right. North American projects call it stationing and write it in hundreds of feet; metric projects call it chainage and write it in kilometres and metres.
At a glance
| Measures | Distance along an alignment from its origin |
| Plus | Offset left or right, at right angles to the alignment |
| US form | Sta. 5+10 = 510 ft |
| Metric form | Ch 1+250 = 1,250 m |
| UK railways (traditional) | Miles and chains (1 chain = 22 yards ≈ 20.1168 m) |
| Belongs to | One named alignment and its revision |
How it is written
| Written | Means |
|---|---|
| Sta. 2+70 | 270 feet from the start |
| Ch 2+340.500, 4.5 m LT | 2,340.5 m along, 4.5 m left |
| 12 m 40 ch | 12 miles and 40 chains |
| Station equation: 12+40.25 back = 12+00.00 ahead | A break where the stationing is reset after a change |
How it is used on projects
Chainage is how designers, surveyors and site teams talk about locations on linear works: a culvert at Ch 2+340, a signal at 12 m 40 ch, a pier at Sta. 5+10. Drainage schedules, earthworks quantities, possession plans and asset registers are organised by it. In IFC 4.3, positions can be referenced to an IfcAlignment, so models carry the same referencing.
Variations
- Increasing direction: chainage usually increases in one direction (for example from London on UK railways, or from a project origin); check which.
- Multiple alignments: carriageways, tracks and utilities may each have their own.
- Linear referencing systems in GIS store positions as route plus measure, the same idea at network scale.
Common mistakes
- Recording a chainage without its alignment name and revision; when the alignment changes, the same number points elsewhere.
- Missing a station equation and reading a chainage twice.
- Mixing feet and metres, or miles and chains, without conversion.
- Locating assets by chainage only, without coordinates as a check.
Where to read more
The highway or railway agency's design manuals for alignment and stationing conventions; the IFC 4.3 documentation from buildingSMART for IfcAlignment and linear placement; and the project's survey and setting-out specification.