You can additionally import data of the PuT supply from a Visum version file (source network) in an existing network (target network). In addition, the infrastructure of the target network can be supplemented. You can set how and with what components the source file is imported.
Use cases
- Transfer of PuT supply data from an external source:
First import public transport supply data from an external source into an empty Visum network using a suitable importer, for example HAFAS or General Transit Feed (GTFS). Then import this data via the PuT supply import.
- Updating the timetable data of models:
External timetable data often do not contain any specific data to distinguish between stop, stop area, and stop point. Once this data has been entered into the network model, this information should not be lost when a current data delivery is transferred (timetable update). The use of the PuT supply import makes it possible to take over the routing of existing line routes and to add new ones.
System requirements
- The calendars of the source and target networks must be compatible for the import:
- Either both networks have the same calendar type No calendar, weekly calendar or annual calendar,
- or there is no calendar in the source network, but there is a weekly or annual calendar in the target network. In this case, the data from the source network is imported with the valid day daily in the target network.
- Both networks are georeferenced:
In case of different projections Visum converts the data of the source network into the coordinates of the target network. The directions of traffic are mapped to each other independently of their names.
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Note: Make sure that the source and target networks contain correctly calculated lengths for line route elements and links. Avoid lengths with the value zero. If the source data set does not contain any length specifications, calculate the length from the geographical position (direct distance) and assign the calculated length to the elements. |
Steps of the import process
The import of PuT supply data is a two-stage process. The reason for this is that the model structure or model references of external PuT supply data usually differ from the model structure of Visum.
In the first stage, the data is imported into an empty Visum network using a suitable importer, for example HAFAS or General Transit Feed (GTFS).
The second stage involves an additive PuT supply import into the loaded network. A second network is opened from a version file and kept in the background during the import. The network loaded in the background is referred to as the source network below and the network visibly loaded for the user as the target network.
In the source network, the following objects can optionally be filtered, other filters are ignored:
- Active vehicle journey sections with the required basic data (valid days, TSys, vehicles, etc.)
- Stops
- Superordinate objects in the line hierarchy
In the target network, you can optionally include a filter on lines, which defines the supply to be replaced. This way Visum deletes all lines that were active in the target network before the import (including all subordinate objects) after the import process has been completed.
Location information is always transferred from the source network to the target network. Visum proceeds in two steps:
Step 1: An isolated view assigns a set of possible locations ("candidates") in the target network to a location in the source network. When selecting candidates, the snap radius and Max. number of candidates per stop event or intermediate point parameters are particularly relevant. If you have allowed the insertion of stop points outside the existing network in the import settings, the transformed position of the source stop point is also inserted as a candidate in the candidate set. This candidate is later inserted into the network as a new stop point with approaching links.
Step 2: By looking at all locations along a line route, one of each of these candidates is selected. The candidates corresponding to each line route element are selected separately for each line route by joint observation along the line route. The path of the line route is determined this way.
If it is not possible to search for candidates by comparing the attributes, a comparison of stop points to nodes can be made using georeferencing.
The edges of a path are allocated with probabilities. The probabilities of the path consist of:
- the position of the candidate and the resulting link length
- the evaluation of how the edge fits into the new network
You define the weights of the various properties before the import. The path with the highest probability is selected as the line route.
Recommended procedure
The set parameters affect all lines to be imported. Global parameters do not always achieve the optimum result for every line. Therefore, proceed step by step:
1. Specify strict parameters.
Only those stop points and line routes are imported whose course is unique. Delete line routes for which these parameters are not suitable from the target network after a manual check.
2. Adjust the parameters and re-import the supply.
Line routes that still exist from the first step are confirmed in this step. New line routes are added due to the changed parameters.
This step-by-step procedure allows you to carry out the necessary quality assurance of the results at the same time.
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Note: In the directory C:\Users\Public\Documents\PTV Vision\PTV Visum 2021/Examples, you can find an example of use on this topic. The example Importer PuT shows different use cases for the (partial) import of public transport supply from another Visum version file. |
