The integration of spatial datasets for network analysis operations

    Network Family
    In the real world there are natural groupings of objects; the various types of roads and paths that make up the road network; rivers, streams, canals, lakes etc. that make up the natural water network; high voltage cables, low voltage cables and transformers etc. that make up an electrical network. With some major exceptions these “families” of objects do not topologically connect with features of other families. The concept of a “network family” is used for establishing the various rules of connectivity between feature types. Features that do not belong to the family cannot connect. This mechanism also provides a simple visual means for the modification of specific connectivity rules and also provides a method for dealing with semantic issues e.g. “street” and “strasse” can both be mapped onto the network family feature “road”.

    A family contains a collection of real-world features that may have connectivity to each other in the same network. The example for a simple road network family is shown below. Road Family Road – Road        via junction
    Road – Trunk Road        via junction
    Road – Slip Road        via junction
    Trunk Road – Trunk Road        via junction
    Trunk Road – Slip Road        via junction
    Slip Road – Motorway        via junction         A matrix representing the connectivity is shown in Figure 5. The first row and column is a list of line type features that may have connectivity. The inner cells show the Point type feature that facilitates connectivity between them.


    Figure 5. The Matrix Table of Road Family

    The family could also be shown as tree structure by setting the root feature. The view of the tree structure varies depending on the root selected. However the relationship between features is still the same. The example of tree structure is show as Figure 6.


    Figure 6. The Tree Structure of Road Family

  • Connectivity across network families
    Network analysis across two families may be required for some applications, e.g. a route planning application may require movement between the road and the rail network families. The network can trace across families if there is a common point connection feature in both families. For instance, a rail station is in both the “road” and the “rail” families and therefore a trace can cross between them via a rail station.
Conceptual Model
Based on the above a conceptual data model was developed. An object-oriented design concept was followed as it allows one to develop models that more closely resembles the real world [19]. The ISO Spatial Schema [10] and the OGC Feature Geometry Specifications [17] were adopted and adapted where necessary. Features have attribute data which is described by alphanumeric data types and treated as a physical property. Geometry and topology are used to describe the shape and continuity of features respectively and are treated as objects relating to a feature. A feature can also have a logical relationship to another feature, and this property is the relationship property. The “Family” contains a collection of features that may connect. Features can be associated with one or more families. Figure 7 gives an overview of the conceptual data model.


Figure 7. Conceptual Data Model

Implementation

Database Model
Once the conceptual data model had been finalised, a physical model was implemented. A simple relational database such as Microsoft Access was chosen to prove the conceptual model. There are six main tables, created for storing spatial data that link to the spatial object. The Family table is used to store the relationship of network connectivity of each family.


Figure 8. Logical Relational Database Model


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