Network Dataset Layer

How to Network Dataset Layer        

A Network analysis layer can not be created without a link to a network dataset, by adding a network dataset layer to ArcMap you are also providing a link to the dataset and can subsequently create analysis layer using the Network Analyst toolbar.

Adding a Network Layer

Add a Network Layer to ArcMap follow the steps:

1) Open ArcMap

2) Click the Catalog Window button on the standard toolbar. The catalog window opens.

3) using the catalog window navigate to the location of the Network dataset and drag it into table of contents. The adding Network Layer dialog box open.

4) Click no to only add the Network dataset to map optionally click yes to add the Network dataset and all it is source feature classes to the map.

The Network dataset is added to ArcMap as a Network layer.

The following list point out which elements a Network layer renders by default when add to ArcMap initially:

• if the network dataset does not have traffic data only edges are displayed.
• if the network dataset has traffic data only traffic is is displayed.
• if time is not enabled traffic for the current time and day is shown.
• if time is enabled traffic for the time specified on the time slider is shown.

        Network element can be queried with the network identify tool on the network analyst toolbar and the identify tool on the tools toolbar. However they cannot be select interactively in ArcMap. Moreover select by attributes, select by location and select by graphics cannot be used to create selection sets on a network layer.

Network Layer Symbology

The symbology of network element can be modified on the network layers Layer Properties dialog box on the Symbology tab.

You can open the Layer Properties dialog box by double - clicking the name of the layer in the Table Of Contents window.

Showing and Hiding Network Elements  

You can show or hide certain types of network element on the map by checking or unchecking them in the show list. When a network dataset supports traffic data, only Traffic is checked by default, otherwise only Edges is checked by default.

What are dirty areas ?

Dirty areas allow you to see where edits to source features have been made since the last time the network dataset was built. Rectangles surround and highlight  the portions of the network dataset that are out of data due to the edits.

When you rebuild the network only the dirty areas are rebuilt, which can be much faster than rebuilding the entire network.

The next peri of graphics demonstrates a scenario in which dirty areas are generated:

if properties of the network dataset are altered the entire network dataset may be covered by a dirty area indicating all the elements of the network need to be rebuilt.

Changing the symbology of edges, junctions, system junctions, turns and dirty areas

you may need to modify the default symbology of items contained within a network dataset layer, the follow steps show how to change the symbology for edges, system junctions. turns and dirty areas ''Changing the symbology for traffic is described later''

1) open the layer properties bialog box by double clicking the network dataset layer in the  arcmap table of contents.

2)  Click the symbology tab.

3) in the show list, click the name of the element that you want to symbolize differently, the element name is selected.

4) in the symbol section to the right click the large button, which show an example of the current symbol on it.

5) use the symbol selector dialog box that opens to define a new symbol for the element.

6) click ok, the symbol selector dialog box closes.

7) click ok, the layer properties dialog box closes.

Displaying traffic

Instructions and tips for displaying traffic are covered in the visualizing traffic topic.

Symbolizing restrictions with arrows

Arrows in a network layer are symbols that can be displayed on edges and traffic elements to mark restrictions. Although any kind of restriction can be symbolized with arrows, it is advised that you only use this dialog box to display prohibit restrictions such as one way street bidirectional streets and streets that prohibit traversal in both directions. To display or prefer- restrictions such as designated road for hazmat you should symbolize your source features accordingly.

The steps below describe how to display arrows:

1) Open the layer properties dialog box by double click the network dataset layer in ArcMap table contents.

2) Click the symbology tab of the layer properties dialog box.

3) In the show list click either edges or traffic to select it.

4) In the symbol section to the right – click arrows, if you are add arrows to traffic click advanced>arrows. The arrows dialog box opens.

5) Check draw arrows on edges.

6) Choose whether you want symbols placed in the middle or at the end of edges

7) From the restriction attribute drop – down list choose the restriction you want to symbolize. 

8) Choose which restrictions cause a symbol to be draw on network edges.

9) Click ok. The arrows dialog box closes.

10) Click ok. The layer properties dialog box closes.

Applying source filters

Source filters allow you to choose a subset of network elements to draw on the map. A previous section demonstrated how to show or hide network elements on the source feature classes they are derived from. You can further limit the drawing of network elements by writing an SQL expression. Only the features that meet the criteria specified in the expression are drawn.

Following steps how to create a source filter:

1) Open the layer properties dialog box by double click the network dataset layer in the ArcMap table of contents.

2) Click the symbology tab of the layer properties dialog box.

3) In the show list click the name of one of the following item; edges, traffic, junctions, system junctions or turns.

4) In the source filters section to the right click the source filters button. If you are adding a source filter to traffic click advanced>source filters. The source filters dialog box opens.

5) In the show sources list check the source feature classes that you want to see in the map display. You can further limit which elements from the source classes are drawn in the map by creating a query expression.

6) Click the name of a source feature class in the show sources list and enter an SQL query using the source query expression pane.

Only features that meet the criteria specified by the query are displayed in the map.

You can repeat this step for any other source feature class in the show sources list.

7) Click ok. The source filters dialog box closes.

8) Click ok. The layer properties dialog box closes.

Other network layer display settings

The network layer supports scale ranges, which specify the scales at which the network layer is visible. These can be set on the general tab of the layer properties dialog box.

The display tab allows you to configure symbols to scale when a reference scale is set. Additionally you can set transparency and map tips for the network layer there. Map tips for a network layer can be used to display either the element ID of network element or the value of any network attribute.