It is important to have accurate measure values along routes, especially when the measures are used to tie in large amounts of event data. You can adjust route measures to correspond with known measure locations using a procedure called calibration. Calibration adjusts route measures using points that contain measure (m)-coordinates. A route can be successfully calibrated with two or more points.
Once you have selected the route that you want to calibrate, you must digitize the points to use for calibration and assign a measure value to each point.
Because one route is calibrated at a time, there is no point-to-route cutoff tolerance specified. All digitized points are assumed to fall on top of the selected route. After all the calibration points have been digitized, you must type the new measure value for each point.
Either whole or partial routes can be calibrated. You can choose to interpolate between the calibration points, extrapolate before or after the calibration points, or use any combination of these methods.
For the measure value on a vertex to be interpolated or extrapolated, a calibration ratio is needed. There are two ways this ratio can be determined. The first method uses the shortest-path distance between the input points. The second method uses the existing measure distance between the input points.
When calibrating disjointed routes, you can choose to ignore the distance of the spatial gap between the parts. If you choose to ignore spatial gaps, route measures will be continuous. If you want the spatial gap incorporated in the measures, the gap distance is the straight-line distance between the endpoints of the parts.
- Click the Editor menu on the Editor toolbar and click Start Editing.
- Click the Edit tool , move the pointer over a route feature, then click the feature.
- Click the Calibrate Route tool on the Route Editing toolbar.
The Calibrate Route dialog box appears.
- Click the Add Calibration Points tool on the Calibrate Route dialog box.
- Click the map at each location along the route where you want a calibration point. Make sure you digitize the calibration points in either route-increasing or route-decreasing order rather than in some random order.
The Calibrate Route Point list populates in the dialog box as you click the points.
- Type the new measure value for each clicked point.
- Click the calibration options you would like to use.
- Click Calibrate Route.