Index Versus Single Files

To save resources, often index files are used. The area is split into a grid of small databases (see Figure 1) and an index file is used as a reference pointer to the individual data files. This accelerates the handling of the data because not always the large file must be read – only the small portion of some small data files. Therefore, we recommend using always index data files.

For topographical databases, the single database file has the extension .tdb (topo data binary). The index file has the extension .tdi (topo data index) and it includes the pointers to the individual .tdb files.

Figure 1. Single database and index database.

The names of the small .tdb files of the index database are arbitrary - but if they are generated automatically during the conversion they have (as default) the same name as the .tdi file but the index is added to the name (if the index file is xy.tdi, then the data files are named xy_column_line.tdb, see Figure 1).