The first implementation question to resolve is how to store the data. We will assume that the data is in a file, and that is uses the same format that the transportation simulation software package Transims () uses. Transims file formats are used several times in this text. The advantage is some degree of portability; the disadvantage is that the formats often contain many more entries than we truly need. Also, a more modern format might use some kind of XML syntax; there is however no corresponding standard for transportation simulations. We think that the advantage of using Transims files outweighs the disadvantages. XML formats will be discussed in Sec. 24.3.
Each Transims network file has a header line, and then zero or more lines of entries. The header line needs to be there; it contains the keys of the entries. Fields are separated by tabs.
The nodes file has the following entries:
0.99nodes
In consequence, a nodes file looks as follows:
{}
ID<tab>EASTING<tab>NORTHING<tab>ELEVATION<tab>NOTES<ret>
1<tab>651700<tab>137200<tab>0<tab><ret>
2<tab>652220<tab>137600<tab>0<tab><ret>
...
The entries which are important for our do-it-yourself implementation are printed in boldface. Any information in the other columns will be ignored. That information may, however, be important to make other Transims modules work, most importantly the visualizer (Sec. 8). In particular, note the additional <tab> that separates a possibly empty NOTES field from the <ret>.
The link file has the following columns. Once more, the relevant ones are printed in bold; the other ones are just given for complete information.
0.99links