TMC/Location Code List
The geographic information used for TMC is distributed in the form of location code lists. Their format is defined in the standard ISO 14819-3. Each country in which TMC is provided issues one or more tables with location codes. These tables are uniquely identified by the country ID (cid) and a table code (tabcd). Within each table each location is identified by a location code (lcd) in the range 1 - 63487. Locations are subdivided into several classes, and within each class into types and subtypes. They fall into three different classes: points, lines and areas. Each location can have references to other locations within the same table. These references indicate, e.g., to which road a bridge belongs, which motorway junctions follow each other or to which administrative area a point belongs.
Common information for all location types
Some information stored in the TMC location tables is common to all locations. This information is used to uniquely identify and to classify every location in a number of different categories.
Country ID, table code, location code
Every TMC location is uniquely identified by three numbers: the country ID (cid), which specifies which country has issued the table containing this location, the table code (tabcd), which enumerates the tables issued by this country, and the location code (lcd), which enumerates the locations listed in this table.
Class, type, subtype
TMC locations are classified in a three-stage system. Each location has a class, which distinguishes between Points, Lines and Areas. The type further separates, for example, points into junctions, points along a road and other POIs. Finally, the subtype provides a detailed classification of different junction or POI categories. These three properties are conventionally written in the form {class}{type}.{subtype}. See TMC/Location Code List/Location Types for a complete list of all combinations defined by the TMC standard.
Points
The most simple TMC location is a point. In contrast to an OSM node, which should correspond to an object whose measures are small, point-like or unknown, TMC point locations can also correspond to extended and complex OSM objects such as motorway intersections, roundabouts, tunnels, bridges or various POIs. TMC points are characterized by the following properties.
Place Name
Point locations are usually accompanied with a place name, which can be the name of a town, motorway junction or POI, depending on the point type and subtype.
WGS84 coordinates
The most important property for finding a TMC point location are its WGS84 coordinates. They are contained in the location table in decimal degrees, multiplied by a factor of 105. Note that these are only approximate coordinates, so the coordinates for larger objects are somewhere inside the area covered by this object, while the coordinates for smaller objects such as junctions of minor roads may also be aside its true position.
Junction number
For points which correspond to junctions or intersections along motorways or other major highways a junction number can be given.
Segment / road references
A TMC point can be part of at most one road. The location code of this road must be present in the same table, and is referenced in the table entry for the point location. It follows that intersections of roads which are both contained in a TMC location table must be represented by one TMC point location for each road.
Road name
If a point is part of a named road, the name of the road can be given.
Intersecting road name
If the point marks an intersection and the road which contains this point is intersected by a named road, the name of this intersecting road can be given.
Offsets
The order of TMC points along a road is marked by offsets. These are references to the neighbouring TMC points along the same road. To each road is assigned a positive and negative direction. The neighbouring TMC points in the positive / negative direction are called its positive / negative offset.
Intersection references
Some countries issue additional information which TMC point locations refer to the same intersection, but belong to different roads. However, this information is not present in all TMC location tables.
Area references
A TMC point can reference an administrative or other area inside which it is located.
Lines
TMC line locations are used to represent roads or road segments. They are very similar to OSM ways since they are constituted by ordered sequences of TMC points or lower order segments.
Road number
Larger roads such as motorways or federal highways are usually identified by a road number or reference number.
Road name
Urban roads are usually identified by a road name.
End place names
Roads or road segments connecting two end points may contain the names of these points. The order of these points in the TMC line location entry also marks the positive direction along this road.
Area references
A TMC line location may have a reference to an administrative or other area containing this road or segment.
Segment / road references
Road segments are part either of a higher order segment or of a road. This containing line location is referenced by its location code.
Offsets
If a road consists of several segments, they form an ordered list, similar to the points along a road. The neighbouring segments along a road are given by the positive and negative offsets.
Areas
TMC Areas can refer to administrative areas, ranging from continents down to communities or villages, or other areas, such meteorological or geographical areas. In contrast to OSM areas, TMC area locations contain no immediate geographical information in the location tables. Their geographical position is to be determined only from their name and from the upward and downward references to containing areas and contained locations of any type.
Name
Every TMC area should have a name which identifies this area.
Area reference
If this area is contained on another area, the containing area is referenced by its location code.