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Geometric Networks

Geometric Networks. Francisco Olivera, Ph.D., P.E. Srikanth Koka Department of Civil Engineering Texas A&M University. Networks. Loop networks. Dentritic networks. Geometric Networks. A geometric network stores line/junction connectivity.

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Geometric Networks

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  1. Geometric Networks Francisco Olivera, Ph.D., P.E. Srikanth Koka Department of Civil Engineering Texas A&M University

  2. Networks • Loop networks • Dentritic networks

  3. Geometric Networks • A geometric network stores line/junction connectivity. • E.g., A water network consisting of water mains, valves, pump stations etc. • To build and edit geometric networks, ArcInfo 8.x or ArcEditor 8.x is needed. • ArcCatalog or ArcToolBox can be used to build geometric networks.

  4. Geometric Networks • ArcMap is used to edit or analyze geometric networks. • Network analysis can be done using the Utility Network Analyst. • To build a new geometric network, right click a feature dataset, then click on New/Geometric Network.

  5. Junction Edge Edges and Junctions • A geometric network consists of edge network features and junction network features. • Edges are network features similar to simple line features. E.g., water mains. • Junctions are network features similar to simple point features. E.g., valves. • Edge – Edge connectivity is built through junctions.

  6. Simple and Complex features • Simple edge features: Edges end with junctions and junctions connect edges. • Complex edge features are created by connecting features to an edge without splitting them at junctions.

  7. Snapping • Snapping is a process moving features. For example making line ends and junctions coincide. • Snap tolerance defines the maximum distance a network feature could be moved.

  8. Sources and Sinks • Sources and Sinks are used to define the flow direction in the network. • Sources are junctions that push the flow away from themselves. • Sinks are junctions that pull flow towards themselves. • An attribute called ‘Ancillary Role’ defines whether a junction is source or sink.

  9. Flow Direction • There are three types of flow directions: Determinate, Indeterminate, Uninitialized. • Determinate flow occurs in as edge if a unique flow direction can be assigned. • E.g. A dendritic stream network. • Indeterminate flow direction occurs in an edge if the flow direction is not unique. • E.g. A transportation network. • Uninitialized flow direction occurs when the flow in a edge is not influenced by sources and sinks. • E.g. A stream network with sources and sinks not defined

  10. Trace Tools • Trace tasks: • Find Common Ancestors • Find Connected • Find Loops • Find Disconnected • Find Path Upstream • Find Path • Trace Downstream • Find Upstream Accumulation • Trace Upstream Downstream Trace Upstream Trace

  11. Network weights • A weight can be defined as the cost for traversing an element in the network. • E.g., pressure loss (per unit length) due to friction in the pipe. • Many to zero or many to one relationships exist between attributes and network weights.

  12. Enabled and Disabled features • Features in a network can be enabled or disabled. • Disabled features act as barriers to flow, whereas enabled features allow the flow to path through. • E.g., due to maintenance of a pipe in the network, it may be disabled temporarily. • An attribute called ‘Enabled’ , set either to 1 or 0, defines enabled or disabled property of each network feature.

  13. Network Connectivity Rules • Rules are set in order to define the connectivity between different network features or/and between different feature types (i.e. sub types). • Types of connectivity rules: Edge – Junction rules and Edge – Edge rules. • Rules can be established such that 10 inch transmission mains connects only to 8 inch transmission mains. • To define connectivity rules right click on the geometric network, click Properties, then click on Connectivity tab.

  14. Network Errors • Illegal geometries might be encountered when building geometric networks. • Common ones: empty geometry, multiple parts, same from and to nodes, zero feature length. • The geometric building wizard automatically determines such features and report such features attributes by creating a new table inside the geodatabase.

  15. Network repairing can be done using Network Editing tools. Common tasks that can be performed: Rebuilding connectivity Repairing connectivity Repairing features with an empty geometry or zero length Repairing features with an identical start-stop vertex Rebuilding features with multipart geometry Repairing Network Topology

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