# What are geometric networks?

Geometric networks offer a way to model common networks and infrastructures found in the real world. Water distribution, electrical lines, gas pipelines, telephone services, and water flow in a stream are all examples of resource flows that can be modeled and analyzed using a geometric network.

## What can you do with geometric networks?

Once a geometric network is modeled, you can benefit from performing various network analyses. The following table lists some of the analyses that can be performed and provides an example of who might benefit from each kind of analysis.

Analysis |
Application |
---|---|

Calculate the shortest path between two points. |
Various kinds of utility companies use this as a method of inspecting the logical consistency of a network and verifying connectivity between two points. |

Find all connected or disconnected network elements. |
Electric companies can see which part of the network is disconnected and use that information to figure out how to reconnect it. |

Find loops or circuits in the network. |
An electrical short circuit can be discovered. |

Determine flow direction of edges when sources or sinks are set. |
Managers or engineers can see the direction of flow along edges, and ArcGIS can use the flow directions to perform flow-specific network analyses. |

Trace network elements upstream or downstream from a point. |
Water utilities can determine which valves to shut off when a pipe bursts. |

Calculate the shortest path upstream from one point to another. |
Environmental monitoring stations can hone in on a source of pollution in streams. |

Find all network elements upstream from many points and determine which elements are common to them all. |
Electric utility companies can use the phone calls of customers experiencing an outage to locate suspect transformers or downed lines. |

If modeling undirected networks fits your needs more than directed or geometric networks, see What is Network Analyst. Transportation networks, such as roads, are best modeled in ArcGIS by network datasets. Working with network datasets and performing analyses on them requires the ArcGIS Network Analyst extension.

## Geometric networks in ArcGIS

A geometric network is a set of connected edges and junctions, along with connectivity rules, that are used to represent and model the behavior of a common network infrastructure in the real world. Geodatabase feature classes are used as the data sources to define the geometric network. You define the roles that various features will play in the geometric network and rules for how resources flow through the geometric network.

In the following graphic, a geometric network models the flow of water through water mains and water services that are connected by junction fittings:

A geometric network is built within a feature dataset in the geodatabase. The feature classes in the feature dataset are used as the data sources for network junctions and edges. The network connectivity is based on the geometric coincidence of the features in the feature classes used as data sources. Each geometric network has a logical network—a collection of tables in the geodatabase that stores connectivity relationships and other information about the features in the geometric network as individual elements for use in tracing and flow operations.

Geometric networks are comprised of two types of features: edges and junctions. Edges and junctions in a geometric network are special types of features in the geodatabase called network features. Think of them as point and line features with extra behavior that is specific to a geometric network. Like other features in the geodatabase, they have behavior such as domains and default values. Since they are part of a geometric network, they have extra behavior such as an awareness that they are topologically connected to each other and how they are connected: edges must connect to other edges at junctions; in the network, the flow from one edge to another is transferred through junctions.

The image below shows an example of a geometric network as it would appear in ArcMap: