Quick Road Network Path AI (QGIS Plugin)

Overview

Quick Road Network Path AI is a QGIS plugin that calculates the fastest path between two user-defined points on a road network using the A (A-star) pathfinding algorithm*.

The plugin dynamically converts a road network into a graph structure, snaps user-selected points to the nearest valid road geometry, and computes an optimal route based on travel time. The resulting path is displayed as a temporary layer and can be exported in multiple formats.

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Features

• Select a road network layer (line geometry).

• Optional boundary layer filtering to constrain routing.

• Interactive selection of start and end points on the map.

• Automatic snapping of points to the nearest road segment.

• Fast route computation using A* algorithm.

• Outputs:

  • Total distance (km)
  • Estimated travel time (minutes)

• Creates a temporary route layer with attributes:

  • id
  • length_km
  • time_min

• Export results to:

  • GeoPackage (.gpkg)
  • Shapefile (.shp)
  • Custom file location

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How It Works

1. Input Selection

• User selects:

  • A road layer (required)
  • A boundary layer (optional)

• User clicks two points on the map:

  • Start point
  • End point

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2. Snapping

Each clicked point is snapped to the nearest road geometry:

• Uses QgsGeometry.nearestPoint()
• Distance is calculated using QgsDistanceArea
• A maximum snapping threshold is applied:

max_snap_distance_m = 1000

If no road is found within this distance, the process stops with a warning.

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3. Graph Construction

The road network is converted into a graph:

• Nodes: road vertices
• Edges: segments between vertices

Each edge stores:

• Length (km)
• Travel time (minutes)

Travel time is computed as:

time = (distance / speed) * 60

• If a speed field exists → it is used
• Otherwise → default speed = 50 km/h

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4. Pathfinding (A* Algorithm)

The plugin uses the A* algorithm to compute the optimal route.

• Cost function → travel time
• Heuristic → Euclidean distance:

h(n) = sqrt((x2 - x1)^2 + (y2 - y1)^2)

This ensures:

• Efficient search
• Optimal solution (fastest path)

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5. Output Layer

The resulting path is:

• Created as a temporary LineString layer

• Added automatically to the QGIS project

• Contains:

  • Total distance
  • Total travel time

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6. Export

Users can export the result via dialog:

• GeoPackage (default temp file)
• Shapefile
• Custom path

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Requirements

• QGIS 3.x
• Python 3.x (included with QGIS)

Input Data Requirements

Road Layer:

• Geometry: LineString / MultiLineString
• Must be topologically connected

Optional:

• speed field (numeric, km/h)

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Installation

1. Clone or download the repository:

git clone https://github.com/your-username/your-repo.git

2. Copy the plugin folder into your QGIS plugin directory:

Windows:

C:\Users\<YourUser>\AppData\Roaming\QGIS\QGIS3\profiles\default\python\plugins\

Linux:

~/.local/share/QGIS/QGIS3/profiles/default/python/plugins/

macOS:

~/Library/Application Support/QGIS/QGIS3/profiles/default/python/plugins/

3. Restart QGIS

4. Enable the plugin:

• Plugins → Manage and Install Plugins → Installed → Enable

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Usage

1. Prepare Data

• Load a road network layer
• (Optional) Load a boundary polygon layer

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2. Run Plugin

• Go to:

Plugins → Quick Road Network Path AI

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3. Set Parameters

• Select:

  • Road Layer
  • Optional Boundary Layer

• Click:

Pick Start and End Points

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4. Select Points

• Click on map:

  • First click → Start point
  • Second click → End point

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5. Results

• Route is displayed on map
• Export dialog appears
• Choose format to save

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Messages & Error Handling

The plugin provides feedback via dialogs:

Warnings:

• No road layer selected
• Failed snapping (no nearby road)
• No path found

Information:

• Instructions for selecting points
• Export confirmation

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Limitations & Notes

• Assumes bidirectional roads

• No support for:

  • One-way streets
  • Turn restrictions
  • Traffic data

• Graph is rebuilt every run (can be slow for large datasets)

• Snapping uses linear search (can be optimized with spatial index)

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Code Structure

Main Class

QuickRoadNetworkPathAI

Key Components

• GUI

  • initGui()
  • create_dock()

• User Interaction

  • pick_points()
  • get_point_from_map()

• Processing

  • snap_to_road()
  • build_graph()
  • a_star()

• Output

  • create_route_layer()
  • export_*()

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License

This plugin is released under the GNU General Public License v3.0 (GPLv3).

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Support and Contribution

• Author: Dimitra Pappa
• Repository: https://github.com/demetrapappa14-geospatial/quickRoadNetworkPathAI
• Issues: Use GitHub Issues for bug reports and feature requests

Contributions are welcome via pull requests.