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OpenLR location dereferencer

Project description


License Build status Coverage Status PyPI - Python Version PyPI

This is a Python package for decoding OpenLR™ location references on target maps.


  • Python ≥ 3.6
  • geographiclib (PyPi package)
  • openlr (PyPi package)
  • For unittests, SQlite with spatialite extension is required


  • ☑ Example map format
  • ☑ Routing
  • ☑ Candidate route rating
  • ☑ Backtracking to get correct routes
  • ☑ Decoding line locations
  • ☑ Decoding 'point along line' locations
  • ☑ Decoding 'POI with access point' locations


It is divided into the following submodules:


Contains an abstract map class, which you may want to implement for your target map.

maps.wgs84 provides methods for reckoning with WGS84 coordinates.


Implements the abstract map class for the example map format used in the unittests and examples


The actual logic for matching references onto a map.

This includes finding candidate lines and scoring them, and assembling a dereferenced location.


The decode(reference, mapreader) function will take a location reference and return map objects.

Usage Example

First, implement the MapReader class for your map. The example_sqlite_map module is an implementation you may look at.

Second, construct a location reference. For instance, parse an OpenLR line location string:

from openlr import binary_decode
reference = binary_decode("CwmG8yVjzCq0Dfzr/gErRRs=")

Third, decode the reference on an instance of your map reader class:

from openlr_dereferencer import decode
real_location = decode(reference, mapreader)

real_location.lines # <- A list of map objects



The configuration value openlr_dereferencer.SEARCH_RADIUS determines how far away from the LRP road candidates are searched. The unit is meters, the default 100.


Every candidate line gets a score from 0 (bad) to 1 (perfect).

There are four scoring weight parameters:

  • GEO_WEIGHT = 0.25
  • FRC_WEIGHT = 0.25
  • FOW_WEIGHT = 0.25
  • BEAR_WEIGHT = 0.25

They determine how much influence a single aspect has on an overall candidate's score.

You may just change them before decoding:

from openlr_dereferencer.decoding import scoring

scoring.GEO_WEIGHT = 0.66
scoring.FRC_WEIGHT = 0.17
scoring.FOW_WEIGHT = 0.17
scoring.BEAR_WEIGHT = 0


openlr-dereferencer logs all mapmatching decisions using the standard library logging module.

Use it to turn on debugging:

import logging


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