Open format for local map data

TomTom of the Netherlands has proposed a new open standard that would allow currently incompatible, localised data, to be more widely used. Called OpenLR, it covers "procedures and formats for the encoding, transmission, and decoding of local data irrespective of the map". As the firm explains in a White paper, the new format allows locations localised on one map to be found on another map to which the data have been transferred. The format used is reportedly compact enough to be practical at slow transmission rates. A dot requires just over seven bytes.

Up to now, OpenLR only describes lines via "shortest paths". One possible application – and the one emphasized by TomTom – is traffic services. The demands that the maps have to fulfil further underline the applicability of the format for this application. OpenLR requires that –

• All routes be assigned to a "functional road class" and all properties – such as "motorway", "roundabout", or "ramp" – be described.
• The coordinates be given in the WGS 84 format.
• Route links be given in metres.

At present, only the specifications for the OpenLR format are available, but they include a detailed description of the encoding and decoding of routes. TomTom plans to release a library for the format under the GPLv2 soon.

(djwm)