1.1. What sDNA is used for¶
sDNA stands for Spatial Design Network Analysis, which does what it says on the tin. Let’s take that one step at a time.
- Network Analysis
A network is a structure defined by nodes, and links between them. Many networks exist in this world: virtual, physical, social, and a huge literature exists on analysing networks.
- Spatial Network Analysis
We define a spatial network to be a network with added spatial information. Nodes have positions in Euclidean two- or three-dimensional space. The links between nodes need not take the most direct route, but can have physical shapes other than straight lines. In sDNA, we focus on analysing links, rather than nodes. Links can have data attached to them.
- Spatial Design Network Analysis
sDNA can be used to analyze any kind of spatial network.
However (...with the exception of one escapade the author had with fish in rivers...) our research focuses on urban networks and transport systems: networks for vehicles, pedestrians (indoors and out), cyclists and public transport. sDNA spans the gaps between transport planning, urban design and architecture.
Measures output from sDNA have been shown to correlate with a wide variety of phenomena including health, community cohesion, land values, town centre vitality, land use, pedestrian, cyclist and vehicle flows, emissions, accidents and crime. sDNA’s high spatial resolution, low data collection cost and applicability to economic, social and environmental problems, makes it particularly suitable for modelling sustainable transport systems; while its ability to handle large networks also makes it suitable for “big data” type analysis.
So, the “Design” part of the sDNA name is there because our aim as researchers is to provide an evidence base for the design of better networks in the built environment.
This leaves me in the awkward position of writing a manual for two audiences! Firstly, the built environment planners, architects, designers and modellers, who want specific details on modelling their system. Secondly, the people modelling other kinds of spatial network, who want to understand the more abstract and mathematical concepts. I have tried to cater to both in this manual; if you are in one group, please feel free to ignore any material which is clearly pitched at the other.
Anyone who is using real world network data will need to learn about the potential pitfalls by reading Network Preparation, and anyone using sDNA will need to read Installation and first usage. It is then possible to start using sDNA without any more reading, though Guide to individual tools exists for a reference if needed. For a quick introduction to the concepts behind sDNA there is Analysis: what the results mean, and for the full details, Analysis: full specification.
Transport, planning and urban design practitioners should start with Network Preparation then Installation and first usage. If you need to get a job done quickly then proceed to Step by step guides for specific tasks; for more in-depth understanding the other chapters await.