It is possible to create routes by merging linear features that share a common identifier.
There are two scenarios for how the route measures can be set:
- Measure values for the input features are not known.
- Measure values for the input features are known.
Measure values are not known
When route measure values are not known, they can be generated by accumulating the digitized length or a numeric attribute value of the input features. If you choose to use digitized length, the units of the output route measures will be the same as the output coordinate system (feet, meters, and so on). If you choose to use a numeric attribute, the output route measures can be any units you want.
When routes are created in this manner, you control the direction that measures are assigned to the routes by specifying the coordinate priority of the starting measure. The coordinate priority can be upper left, upper right, lower left, or lower right. These options are determined by placing the minimum bounding rectangle around the input features that are going to be merged to create one route.
In the example below, measure values are obtained by accumulating the values in the MILES field. Note that the digitized direction of the input features does not matter because a starting priority is given. In this example, the starting priority is lower left.
Routes with multiple, disjointed parts are supported. A route representing a road, for example, might have the same name on either side of a river. For situations like this, you can choose to ignore spatial gaps between parts when creating routes. If you choose to ignore spatial gaps, route measures will be continuous when a disjointed route is created. If you want the spatial gap incorporated in the measures, the gap distance is the straight-line distance between the endpoints of the parts. The units of the gap will be that of the output coordinate system, which may or may not be the same as the measure units.
When creating disjointed routes, you can choose to have the measures be continuous or discontinuous. In the example below, the starting priority is lower left.
Measure values are known
When measure data already exists as attributes of the input linear features, it is possible to create routes that inherit this measure information. In the following example, two fields could exist that store from- and to-mile information.
When using this method, it is important to orient each input linear feature in the direction of increasing measure to prevent routes that have measures that do not always increase.
Measure values are obtained by using the values in the FR_M and TO_M fields. Note in the diagram below that the digitized direction of the input features determines the direction of the output route.