PyLR, an OpenLR decoder in python

4 décembre 2014 Non Par Equipe Technique

Here, at Mappy, we have decided to release our implementation of the OpenLR specification.

To make a story short, OpenLR is an open source software project launched by TomTom in september 2009. This is an attempt to provide a location referencing method that works between digital maps of different vendors or versions.

We use traffic informations from 10 countries in Europe in DATEX format, location reference was provided using the TMC reference system. The problem with TMC is that the coverage of the road network is relatively less than optimal. Because TomTom was providing information on a larger portion of the road network (in theory, the whole network could be covered) using its OpenLR scheme, we have decided to drop TMC in favor of OpenLR.

The basics :

OpenLR data provide paths or that must be “decoded” on the destination network (also called ‘map’ in the OpenLR terminology) by computing the shortest path between location reference points and a bunch of values representing the physical properties of the network at these points.

So, what is PyLR ?

PyLR is a partial Python implementation of the OpenLR specification largely inspired from the reference implementation in Java (available on the OpenLR site).

It is partial in the sense that only parser/decoder is provided, encoding et serializing OpenLR data is not supported at the moment.

While still a work in progress, it is actually used in production here at Mappy. For information, our implementation fail to decode less than 1% of the collected traffic situations, which correspond mostly to mismatched data with our network database.

PyLR implement a decoder from the binary/base64 data representation (xml is not handled at the moment). It implements also a decoder that use an abstract representationof the targeted map.

At the moment, PyLR is not really usable out of the box: you still need to implement a concrete database and a shortest path algorithm for playing with the library.

As stated before, it is a work in progress, we have plan to provide more tools for testing and playing around with the lib: stay tuned !!!!

PyLR is available on github and is released under the Apache licence, version 2.