Flow Map

$image\flowmap.gif$ Flow maps show the movement of people, commodities, animals, or other data from one location to another. These maps show data based on routes of travel and vary line thickness to show amount of travel. The greater the movement, the thicker the line. MapViewer can draw lines from centroid to centroid to create a flow map, or associate a data file with a base map of polylines to create a flow map design.

Creating and Editing a Flow Map

Click the Map | Create Map | Flow command to create a flow map. Edit flow map properties in the Property Manager.

See Creating and Editing Thematic Maps for information on creating a flow map, changing a flow map to another map type, and changing map properties.

Flow Map Properties

The Property Manager has General, Data Labels, Info, and Map pages for editing flow maps. Click the preceding hyperlinks for information on properties in each of the property manager pages.

Map Page

The Map page in the Property Manager for a flow map contains method, data, line, and label properties.

Edit flow map properties in the Map page of the Property Manager.

General

The General section of the Map page contains the method, data, and class properties. Select Apply to polylines or Connect centroids for the flow map method in the Method list.

The Connect centroids method connects boundary object centroids based upon starting and ending primary IDs. You can connect the centroids of polygons, polylines, or points.
The Apply to polylines method applies flow map properties to polyline objects associated with a data file. Each polyline must be associated with a primary ID and data value. This method is useful for mapping direct line data, such as traffic volume or river flow.

Start PID	End PID	Flow Data
AZ	FL	17
AZ	TN	5

Data for the Connect centroids method should be similar to the above format.

PID	Flow Data
Polyline1	17
Polyline2	5

Data for the Apply to polylines method

should be similar to the above format.

Select Proportional or Use classes for the flow line property method in the Data list. The Proportional method draws flow lines with the same color and style and varies the line width based on the data value. The Use classes method applies properties to flow lines based on classes specified in the Classes dialog.

Open the Classes dialog to specify data classes by clicking the button in the Classes field. If the Proportional method is selected in the Data field, the Classes box is disabled.

Line

Edit line properties for flow maps in the Line section of the Map page. If the Use classes method is selected in the Data field, the line properties are disabled in the Property Manager and the flow lines are edited in the Classes dialog.

Set the Min width and Max width for the Proportional data method by typing a value in page units or clicking the buttons. The flow line with the smallest data value is sized by the Min width value, and the flow line with the largest data value is set to the Max width. The other flow lines are sized proportionally between the minimum and maximum widths.

See the line properties help page for more information on editing flow line properties.

Labels

Labels are added in the Labels section of the Map page. Labels cannot be added to a flow map drawn with the Apply to polylines method. Click the Draw labels check box to show labels for the flow lines.

Select PID, Value, or PID and value from the Label type list to select the information displayed on the flow line label. The PID option shows the start and end object PIDs. The Value option shows the value for the flow line. The PID and value option shows both start and end PIDs and values separated by a colon.

When the Data property is Proportional, edit the labels' font properties in the Front Properties section. See the Text and Font Properties help page for more information on editing font properties.

Leader Line

Leader lines are added in the Leader Line section of the Map page. Leader lines cannot be added to a flow map drawn with the Apply to polylines method. Click the Draw leader line check box to draw leader lines between the flow lines and labels.

When the Data property is Proportional, edit the leader line properties in the Line Properties and End Styles sections. See the Line Properties help page for more information on editing line properties.

Labels and Leader Lines when Using Classes

Edit label and leader line properties in the Classes dialog when the Data property is Use Classes.