ogrlineref

What is ogrlineref?

ogrlineref is the GDAL utility for linear referencing on polyline data. It can segment a line feature into a series of "parts" each carrying begin and end measure values, locate a given distance along a line and emit the corresponding point, or extract a sub-part of a line between two measure values. It is the command-line answer to typical LRS workflows on roads, pipelines, rails, and rivers.

ogrlineref [options] <mode-flags>

Main modes (pick one):

• -create — build a parts layer by segmenting a line with a stations layer
• -get_pos — find the measure position of a point along a line
• -get_coord — find the point at a given measure along a line
• -get_subline — extract a sub-section between two measures

Commonly used options:

• -src <path> / -src_layer <name> — source line dataset
• -spf <path> / -spf_layer <name> — stations (points) dataset for -create
• -dst <path> / -dst_layer <name> — output dataset
• -f <format> — output driver
• -s <step> — segment length (metres) for -create
• -mb <value> / -me <value> — begin/end measure for -get_subline
• -x <value> / -y <value> — point coordinates for -get_pos
• -m <value> — measure for -get_coord
• -progress — show progress

When would you use ogrlineref?

Use ogrlineref for LRS tasks that go beyond simple length calculations. Typical jobs: creating a parts layer that breaks a road centreline into 100-metre segments with begin_pos/end_pos measures for mapping accident hot-spots (ogrlineref -create -src road.gpkg -dst parts.gpkg -s 100), locating a specific kilometre post on a rail corridor (-get_coord -src rail.gpkg -m 45000), or clipping a pipeline to a section of interest (-get_subline -mb 1200 -me 1800).

For heavier LRS workflows — mile-post referencing, cross-section measurement, route event tables — consider PostGIS with its linear-referencing functions or dedicated transportation-GIS tools. ogrlineref covers the classic command-line needs but is not a full LRS engine.

FAQs

What units are the measures in?

Whatever the source line's CRS uses horizontally — metres in a metric projection, degrees in WGS84 (which is rarely what you want). Reproject to a metric CRS with ogr2ogr -t_srs EPSG:3857 or a local metric system before using ogrlineref if you want kilometres or miles to line up with reality.

How do I create 1-km mileposts along a corridor?

Use -create with -s 1000 (metres). The output parts layer will have evenly-spaced segments. To get point features at each kilometre mark rather than segments, post-process with ogr2ogr -sql "SELECT ST_StartPoint(geom) FROM parts" -dialect SQLite or use a dedicated milepost generator.

How do I find the chainage of an off-line point?

Use -get_pos -src line.gpkg -x <x> -y <y>. The tool projects the point onto the nearest line vertex (or segment) and returns the measure there. Note this is a simple projection onto the line — for multi-line networks or for points far from any line, results may be surprising.

When should I use ogrlineref vs PostGIS?

ogrlineref is convenient for file-based workflows and one-off jobs. PostGIS ST_LineLocatePoint, ST_LineSubstring, and the full LRS extension give you persistent, indexable, queryable LRS in the database — the right choice for any serious transportation or utility LRS deployment.