Interchange Format
Map providers generally collect, aggregate and supply data in a well-defined and documented file format that is specifically intended for information interchange, e.g. Navteq uses Standard Interchange Format (SIF) and GDF, while Tele Atlas uses a proprietary form of GDF. It is usually in a plain-text form (ASCII) consisting of fields that are easily parsed and interpreted by the various parties who will handle it. The portable format allows additions, deletions and modifications to be readily performed by simple text-editing programs.
A small number of record types are used to represent the various types of data. Each record type consists of a sequence of fields, which are either fixed length or delimited by a punctuation character such as a comma. For example, a link entity could be represented by a record of the form:
where type1 defines this as a link record type and label serves as an identifier to distinguish this link from all others. The z1 and z2 fields determine the vertical separation of this link from others sharing the corresponding nodes node1 and node2. Thus an overpass to a link, for example, can be represented as not connected to that link. Other record types are used to represent address information, shape-points for a link, cities and states, points of interest (POI’s), etc.
The interchange format for a map database is not organized well for use by a navigation unit during runtime. Records are in an arbitrary order and therefore difficult to search and data, such as street names and coordinate values, are repeated from record to record. Consequently the database content is reorganized into a binary form more suitable for run-time operation.
Read more about this topic: Map Database Management
Famous quotes containing the word interchange:
“What men have called friendship is only a social arrangement, a mutual adjustment of interests, an interchange of services given and received; it is, in sum, simply a business from which those involved propose to derive a steady profit for their own self-love.”
—François, Duc De La Rochefoucauld (1613–1680)