Preparing a network#

Open AequilibraE > Model building > Network preparation from the menubar or dock panel. This interactive tool prepares node and link layers without requiring an open project. See Model building for the workflow and project creation dialogs.

Project import requirements#

Project creation requires link direction, allowed modes, and link type values. Both importers compute a_node, b_node, and distance from geometry. These fields do not need to exist in the source link layer.

The interactive layer importer accepts link and node layers with field mappings. Map node_id and is_centroid from the node layer. You can supply unique link IDs or select Initialize? to generate them.

The Processing Create project from link layer algorithm generates nodes from link endpoints and assigns its own link IDs. Its optional source ID mapping preserves input identifiers in source_id. Use Add or renumber centroids from layer afterward to assign centroid IDs from a point layer.

Network articulation#

Use LineString geometries for network links. Convert MultiLineString features to LineString features before using network preparation. The first endpoint corresponds to a_node and the last endpoint corresponds to b_node. The network preparation dialog creates or matches nodes and adds these endpoint IDs to copied link layers.

Standalone algorithms, such as Processing Shortest path, operate directly on network layers. Their link inputs need link_id, a_node, b_node, direction, modes, and the selected numeric cost field. This requirement differs from project import, which computes endpoint IDs in the project database.

Direction#

Link direction uses three integer values:

  • -1 permits flow from B to A only.

  • 0 permits flow in both directions.

  • 1 permits flow from A to B only.

Distance#

Project imports compute link distance in meters from geometry and ignore source distance values. For a standalone path calculation, supply a numeric cost field such as distance or travel time in the input layer.

Modes#

Each network mode has a one-letter ID, which can be uppercase or lowercase. A link’s modes value combines the IDs of all modes permitted on that link. For example, ctbw permits car, truck, bicycle, and walking modes when the project defines those IDs. The order of IDs does not matter.

New projects include default modes from the parameters file. Layer importers also create missing modes from the input values. Use Data > Add mode to add a mode to an existing project. OSM import uses mode names such as car and walk instead of one-letter IDs.