Theory of nodes and urban networks
Introduction
A spatial network (sometimes also called geometric graphs")) is a graph&action=edit&redlink=1 "Graph (discrete mathematics) (not yet drafted)") in which the vertices") or edges (graph theory)&action=edit&redlink=1 "Edges (graph theory) (not yet drafted)") are spatial elements associated with geometric objects, for example, the nodes are located in a space equipped with a certain metric&action=edit&redlink=1 "Metric (mathematical) (not yet written)." a pair of nodes are connected if the Euclidean distance") is less than a given neighborhood radius. Mobility and transportation networks"), Internet, cell phone networks, power lines"), social and contact networks, and neural networks are all examples where the underlying space is relevant and where the topology of the graph alone does not contain all the information. Characterizing and understanding the structure, resilience, and evolution of spatial networks is crucial for a multiplicity of fields ranging from urban planning to epidemiology.
Examples
An urban spatial network can be constructed by abstracting intersections (nodes) and streets (vertices), something that is usually referred to as a transportation network&action=edit&redlink=1 "Transportation network (graph theory) (not yet written)"). Beijing traffic was studied as a dynamic network and its filter properties have been useful for identifying systematic bottlenecks[3].
One might think of a 'space map' as the negative image of a standard map, with open space cut out from the background of buildings or walls.[4].
Characterizing spatial networks
The following aspects are some of the most characteristic to examine in a spatial network:[1].
In many applications, such as roads, highways, and other transportation networks, the network is assumed to be flat. Flat networks constitute an important group within spatial networks, but not all spatial networks are flat. In fact, passenger airlines are a non-flat example: All airports in the world are connected by direct flights.
There are many examples of networks that appear not to be "directly" embedded in space. Social networks, for example, connect individuals through friendship relationships. But in this case, space intervenes in the fact that the probable connection between two individuals usually decreases with the distance between them.