Spatial Design Network Analysis (sDNA/sDNA+) Manual

This is the manual for sDNA, the spatial network analysis toolbox for GIS and Python.

This manual can be cited as follows:

Cooper, C. (2024) Spatial Design Network Analysis (sDNA) version 4.1 Manual. Cardiff University. Available, http://sdna.cardiff.ac.uk/sdna/software/documentation

Please also remember to cite the software itself in any published sDNA analysis:

Cooper, C.H.V., Chiaradia, A.J.F., 2020. sDNA: 3-d spatial network analysis for GIS, CAD, Command Line & Python. SoftwareX 12, 100525. https://doi.org/10.1016/j.softx.2020.100525

Further help, feature requests, bug reports, errata: If you have any general questions about using sDNA, requests for features, or problems with the software or manual, please get in touch via our website.

Acknowledgements: This manual was originally put together under an Impact Accelerator grant from the Economic and Social Research Council. The principal investigator was Alain Chiaradia and the co-investigator Crispin Cooper, based at Cardiff University department of Geography and Planning and the Sustainable Places Research Institute.

As of 2024, the previously proprietary sDNA+ software has been merged with the open source sDNA Open. All features are now open source - enjoy! While this manual uses sDNA to refer to the software, sDNA+ can now be used interchangeably.

Table of Contents

• 1. Introduction
  • 1.1. What sDNA is used for
  • 1.2. Research Evidence
• 2. Network Preparation
  • 2.1. Principles
    • Data in a misleading format
      • Connectivity rules
      • Spatial reference
    • Connectivity errors at key locations
      • Cluster tolerance
      • Intersections and overlaps
      • Incorrect grade separation, elevation and oneway data
      • Definitive check for connectivity errors
    • Geometry errors at key locations
      • Traffic islands
  • 2.2. Tools
    • Break intersections
    • Shared point line breaker
    • Topology
  • 2.3. Notes on specific formats
    • Address point data
    • OpenStreetMap (OSM)
    • Pedestrian networks
• 3. Analysis: what the results mean
  • 3.1. Links and network radius
  • 3.2. Betweenness
  • 3.3. Closeness
  • 3.4. Other measures
  • 3.5. Summary of measures
  • 3.6. Calibration
• 4. Analysis: full specification
  • 4.1. Definitions
    • Link
    • Polyline
    • Junction
    • Distance Metric
    • Radius
    • Geodesic
  • 4.2. Weighting
  • 4.3. Handling of one-way systems
  • 4.4. Mathematical definition of outputs
    • Notation
    • Centrality measures
      • Farness
      • Closeness
      • Mean geodesic length
      • Network quantity penalized by distance (gravity model)
      • Betweenness
      • Two phase betweenness
      • Two phase destination
    • Network detour analysis
      • Mean Crow Flight
      • Diversion Ratio
    • Network shape analysis
      • Convex Hull Area
      • Convex Hull Perimeter
      • Convex Hull Maximum Radius
      • Convex Hull Bearing
      • Convex Hull Shape Index
    • Radius description measures
      • Links
      • Length
      • Weight
      • Angular Distance
      • Junctions
      • Connectivity
    • Individual polyline descriptive measures
      • Line Length
      • Line Connectivity
      • Line Angular Curvature
      • Line Hybrid Metrics
      • Line Sinuosity
      • Line Bearing
      • Link Fraction
  • 4.5. List of outputs and abbreviations
• 5. Troubleshooting Models
  • 5.1. Is the model wrong, or am I?
    • Links with low flow in the model which we didn’t expect
    • Links with high flow in the model which we didn’t expect
• 6. Installation and first usage
  • 6.1. Requirements
  • 6.2. Installation
    • ArcGIS 10.x
    • ArcGIS Professional
    • QGIS
    • Advanced sDNA models in Autocad Map3d
    • Using sDNA from the command line
      • Troubleshooting
    • Using sDNA through the Python interface
• 7. Guide to individual tools
  • 7.1. Options common to multiple tools
  • 7.2. Individual tool details
    • Preparation
      • Prepare network
      • Individual Line Measures
    • Analysis
      • Integral Analysis
      • Specific Origin Accessibility Maps
      • Integral from OD Matrix (assignment model)
      • Skim Matrix
    • Geometries
      • Convex Hulls
      • Geodesics
      • Network Radii
    • Calibration
      • Learn
      • Predict
  • 7.3. Advanced configuration and command line options
    • Advanced config options for sDNA Prepare
    • Advanced config options for sDNA Integral and geometry tools
    • Preset metric variables
    • Interpretation of one way data
    • Hybrid analysis
    • Expression reference
    • Creating a zone table or matrix file
      • 1d table in list format
      • 2d table in list format
      • 2d table in matrix format
    • Zone Data and Zone Sums
• 8. Step by step guides for specific tasks
  • 8.1. Downloading and preparing data from OpenStreetMap
  • 8.2. Modelling a combined vehicle and cycle network
    • Production of a routable network
    • Running the vehicle network model
    • Calibrating the vehicle model
    • Production of the cycle model
    • Calibration of the cycle model
    • Recommended model outputs
      • Predicted vehicle flows
      • Predicted cyclist flows
      • Accessibility
      • Effect of traffic and slope on accessibility
      • Effect of traffic on accessibility
      • Predicted conflicts
      • Flows to/from specific facilities
      • Accessibility to/from specific facilities
      • Change to accessibility caused by proposed scheme
    • Displaying model outputs