GDMS-Topology is an OSGi plugin that brings shortest path calculations and network analysis functionality to OrbisGIS.Underneath the hood, GDMS-Topology uses Java-Network-Analyzer.
Networks (transportation, hydrological, etc.) are represented as mathematical graphs which may be considered to be directed, edge-reversed or undirected. For directed (and reversed) graphs, the user may specify individual edge orientations. The user may specify individual edge weights, or omit them to consider the graph as unweighted.
Optimized algorithms are provided for computing distances:
- One-to-One: Source to destination
- One-to-All: Source to all possible destinations
- Many-to-Many: Distance matrices
The user provides a list of destinations. The function calculates the distance from every node in the graph to each of the possible destinations and chooses the closest destination. This is particularly useful for generating isochrone accessibility maps.
Network analysis:ST_GraphAnalysis
In order to study the global structure of a network, it is possible to calculate the following standard centrality measures:
ST_StrahlerStreamOrder: Strahler stream order for hydrological networks