Linear Referencing
The road is one-dimensional, and its data is numbered accordingly.
Every highway, railway, pipeline and river of any size is managed by position along a route rather than by coordinate, because an asset record outlives the geometry it was digitised against. That gives the data its own arithmetic: measures that are not lengths, numbering that skips where the road was rebuilt, and an M ordinate that most software drops without saying so. These guides start with routes, measures and events, and with what a postmile actually encodes; then read a real published LRS, locate points on it, place events from their measures, cut routes between two of them, overlay event tables, aggregate and transfer them, build measures where none exist and draw the result as a strip map — with the fixes for measures that run backwards, points that snap to the wrong carriageway, measures with no route under them, and measures lost on the way out.
Step four is the one that changes how the rest reads: once measures are understood as a calibrated register rather than a proportion of the line, every later operation is a lookup against stored values instead of an estimate.
Start here
The cornerstone guide — the whole workflow end to end. Everything after it goes deeper into one part of it.
Step 1 Linear Referencing Explained: Routes, Measures and Events linear referencing explained Begin the path →The full path, in order
The concepts underneath the work, then each task, then the errors that task produces. Work down, or jump to the step you need.
- M Values Explained: Geometry That Carries a Measure m values geometry measure 🧭 Concept
- Postmile and Milepost Systems Explained postmile milepost system explained 🧭 Concept
- Route Calibration Explained: Why Measures Are Not Lengths route calibration measures 🧭 Concept
- Dynamic Segmentation Explained dynamic segmentation explained 🧭 Concept
- LRS Conflation Explained: Moving Events Between Networks lrs conflation explained 🧭 Concept
- How to read a linear referencing system in Python read linear referencing system python ⚙️ How-To
- How to find the measure of a point on a route point measure on route python ⚙️ How-To
- How to find the point at a given measure on a route milepost to coordinate python ⚙️ How-To
- How to extract the part of a route between two measures extract route between measures python ⚙️ How-To
- How to overlay linear event tables in Python overlay linear events python ⚙️ How-To
- How to aggregate events to route segments aggregate events per mile route ⚙️ How-To
- How to transfer events between two route systems transfer events between route systems ⚙️ How-To
- How to build measures onto a line that has none build measures on a line python ⚙️ How-To
- How to draw a strip map of events along a route strip map route events python ⚙️ How-To
- Route measures are not monotonic route measures not monotonic 🔧 Fix
- A point snaps to the wrong carriageway point snaps wrong carriageway 🔧 Fix
- An event's measure falls outside the route milepost outside route range 🔧 Fix
- M values are lost when you export the route m values lost export 🔧 Fix
- Event lengths do not add up to the route length event lengths do not sum route 🔧 Fix
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