Processing algorithms

The plugin adds the provider RoadNetwork to the QGIS Processing toolbox (menu Processing / Toolbox). Most of the algorithms are also available with the buttons of the toolbar and panels.

Group	Algorithm	Usage
Configuration	Configure plugin	Choose the PostgreSQL connection of the project
Structure	Create database structure	Install the schema road_graph in the database
Structure	Upgrade database structure	Upgrade the schema after a plugin upgrade
Administration	Create database local interface	Create the QGIS administration project
Editing	Import data from template	Fill an empty road graph from edges and markers layers
Editing	Clone data to a new editing session	Copy the data of an editing session area into the sandbox
Editing	Merge editing session data	Merge the sandbox data into the production data
Editing	Update managed objects from the road graph	Calculate the references from the geometries, or the geometries from the references, of a layer
Linear referencing	Get road sections from a line (GPS track)	Get the sections of the roads followed by lines, for example GPS tracks

All the algorithms have a parameter PostgreSQL connection to the database: by default, the connection chosen with the algorithm Configure plugin.

Configuration

Configure plugin

Choose the PostgreSQL connection used by the current QGIS project. It must be run before the other algorithms. See Configure the plugin.

Structure

Create database structure

Install the schema road_graph, with its tables, views and functions, and the editing schema road_graph_editing. See Create the database structure.

Upgrade database structure

Upgrade the database structure to the version of the plugin, after a plugin upgrade. The administration panel shows if an upgrade is needed. See Upgrade database structure.

Administration

Create database local interface

Create a QGIS administration project with all the layers, styles, labels and actions. See Create your database local interface and Administration project.

Editing

Import data from template

Fill an empty road graph from an edges layer and a markers layer. The roads, nodes, edges and markers are created, and the references of the edges are calculated. See Import the road graph.

Clone data to a new editing session

Copy the production data located inside the last editing session polygon with the status created into the editing schema road_graph_editing, the sandbox. The status of the session becomes cloned.

Also available with the toolbar button Clone data to the editing sandbox and with the action Create editing session of the editing_sessions layer.

The algorithm refuses to run if:

• the editing_sessions layer is in editing mode: save the changes and stop the editing beforehand,
• an editing session with the status edited has not been merged or dropped yet,
• there is no editing session with the status created: draw the editing session polygon beforehand.

See Road graph editing.

Merge editing session data

Merge the data of the editing session with the status edited into the production schema road_graph, update the managed objects impacted by the changes, then empty the sandbox and delete the merged editing session.

Also available with the toolbar button Merge editing sandbox data.

The algorithm refuses to run if the editing_sessions layer cannot be found or is in editing mode, or if there is no editing session with the status edited.

See Road graph editing.

Update managed objects from the road graph

Update the references or the geometries of the features of a vector layer from the road graph. The layer can be a PostgreSQL table of the database, or any other vector layer, for example a GeoPackage layer.

Parameters:

• Input vector layer: a point or (multi)linestring layer,
• Update policy:
  • Update references: the references of each feature are calculated from its geometry,
  • Update geometries: the geometry of each feature is calculated from its references,
• Update geometries - Preserve start & end points when updating line geometries: No or Yes. Used only to update the geometries of a line layer:
  • No: the geometry is calculated from the stored references,
  • Yes: the references are first calculated from the start and end points of the line, then the geometry is calculated from them. The line keeps its start and end points, and follows the road between them. Use it when the start and end points are right but the references are outdated or the line does not follow the road,
• Output layer: the layer created with the updated features.

The input layer must have the reference fields corresponding to its geometry type:

• point layers: road_code, marker_code, abscissa, and optionally offset, side and cumulative,
• linestring layers: road_code, start_marker_code, start_abscissa, end_marker_code, end_abscissa, and optionally offset and side.

The algorithm supports the in-place editing of the input layer: select the layer, toggle its editing mode, then use the button Edit Features In-Place of the Processing toolbox. The features are then updated directly in the layer, and the changes can be checked before saving them.

For the tables registered in the managed_objects layer, the same updates can be done with SQL, see Calculate the references. They are also done automatically when an editing session is merged, see Update rules.

Linear referencing

Get road sections from a line (GPS track)

Get the sections of the roads followed by each line of a layer, for example GPS tracks imported from GPX files, with the start and end references of each road.

For each line, the algorithm:

1. snaps the line on the road graph edges, without zigzags between close roads, with the database function road_graph.get_snapped_line_from_track,
2. gets the ordered list of the roads followed by the snapped line, with the database function road_graph.get_road_sections_from_snapped_line.

See GPS tracks for the details of these functions.

Parameters:

• Input line layer (GPS tracks): a line or multiline layer, in any coordinate reference system. For a GPX file, open its layer tracks,
• Snap the lines on the road graph: checked by default. Uncheck it only if the lines already follow the road graph edges, for example the result of a previous snapping,
• advanced parameters, used to snap the lines:
  • Distance between the points added to the line (m): 2 by default,
  • Maximum distance between the line and the roads (m): 25 by default. The points of the line further from any road are ignored,
  • Penalty applied each time the road changes: 100 by default. Increase it if the result still has zigzags between close roads,
• advanced parameter Maximum distance between the snapped line and the edges (m): 1 by default,
• Road sections: the output layer.

The output layer contains one feature per road section, in the coordinate reference system of the road graph. Its geometry is the part of the snapped line on this road, and its fields are the fields of the input line, followed by:

Field	Description
road_order	Order of the section along the line, from 1
road_code	Code of the road
start_marker, start_abscissa	References of the start of the section, e.g. 14 and 905.27 for PR 14 + 905.27 m
start_cumulative	Cumulative distance from the start of the road to the start of the section
end_marker, end_abscissa	References of the end of the section
end_cumulative	Cumulative distance from the start of the road to the end of the section
direction	downstream if the line follows the road direction, upstream otherwise
length	Length of the section in meters

If a field of the input layer has the same name as one of these fields, for example road_code, the field of the section is renamed with a suffix, e.g. road_code_2.