Creating a water network using ESRI software

The OS MasterMap Water Network Layer data can be used in two types of networks.

Geometric network

Geometric networks offer a way to model common networks and infrastructures found in the real world. Water distribution and water flow in a stream are two examples of resource flows that can be modelled and analysed using a geometric network.

A geometric network can be set up easily, does not need an additional license and has some functionality (tracing up/downstream, for example) provided by the Utility Network Analyst Toolbar.

Network analyst

Network analyst is the mathematical processing of the geometry of a link/node layer, enabling the identification of all possible routes around that network, along with the distances and times involved. Put simply, this means that, using an accurate road data layer, the computer can identify possible routes between two locations and calculate the shortest route.

This requires a Network Analyst License. You can build simple networks, but more complicated networks will require you to have detailed knowledge of networks to set up attributes and elevators.

Building a geometric network

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 following step-by-step instructions will guide you through building a geometric network; they have been prepared using ArcMap version 10.6.1.

1. Open ArcCatalog.

2. Navigate to your geodatabase in your Folder Connections.

3. Expand the geodatabase.

4. Right-click on the geodatabase, select New from the list of options, then click Feature Dataset…

1. Give your new Feature Dataset a name, then click Next.

1. Set your coordinate system that will be used for the XY coordinates in the data (British National Grid EPSG:27700), then click Next.

1. Set your coordinate system that will be used for the Z coordinates in the data (Newlyn). Ordnance Datum Newlyn (ODN) is our national coordinate system for heights above mean sea level (orthometric heights).

2. Click Next.

1. In the next panel, leave your XY tolerance as the default settings and click Finish. A new Feature Dataset will appear in the geodatabase.

1. Copy the HydroNode and WatercourseLink feature classes into the new Feature Dataset by simply dragging them in.

2. You may get an error message if the coordinate systems of the feature classes don’t match those of the new Feature Dataset. To resolve this, right-click on each feature class and select Properties. Check that the Z coordinate system is set to Newlyn and the XY coordinate system is set to British National Grid, then copy the feature classes into the new Feature Dataset.

1. Right-click the Water feature dataset in the geodatabase, select New from the list of options, then click Geometric Network.

1. Click Next in the New Geometric Network dialog box that opens.

1. Type the name of your geometric network into the text box under the Enter a name for your geometric network section.

2. Select Yes for the snap features within the specified tolerance option.

3. Type 0.5 in the text box next to Meters.

4. Click Next.

1. In the next panel, you must select which feature classes in the feature dataset will participate in the geometric network. Click Select All. All the feature classes in the list will participate in the network.

2. Click Next.

1. The option to exclude features with certain attributes makes it easier to manage the network. In the next panel, you need to opt not to exclude features. Click No, so that all features will participate in the geometric network.

2. Click Next.

1. In the next dialog box, you must specify which line classes will become complex edge feature classes in the geometric network. Complex edge features are not split into two features by the connection of another feature along their length; thus, they are useful for modeling water mains, which may have multiple laterals connected to them. By default, all line feature classes are simple edge feature classes. In the same dialog box, you must specify which, if any, of the junction feature classes can act as sources and sinks in the network. Sources and sinks are used to determine the flow direction in the network.

2. In the row for the HydroNode feature class, click Simple Junction under the Role column.

3. In the row for the WatercourseLink feature class, choose Complex Edge from the list under the Role column.

4. In the row for the HydroNode feature class, click the dropdown menu under the Sources & Sinks column, then click Yes.

5. Click Next.

1. This geometric network does not require weights, which is the default, so click Next in the following panel:

1. Clicking Next opens a summary page. Click Finish after you review the summary page.

2. A progress indicator will appear displaying the progress for each stage of the network-building process. You will receive an error message indicating that the network has been built but contains some errors:

1. Click OK to close the error message box.

2. You can see what errors occurred while building the geometric network by previewing the WaterNet_BUILDERR table.

3. Right-click the WaterNet_BUILDERR table in the Catalog and click Item Description. Then click the Preview tab to view the entries in this table.

4. Features with invalid geometries are identified during the network build progress and recorded in the Network Build Errors Table. (This is user-managed; it does not get updated when the features listed within it are edited.)

5. If you received more than two errors, delete the geometric network and repeat the steps to create it again.

6. You can then proceed to load the data into ArcMap.