How To: Expose route M values (geometry) as attributes for route re-calibration


M values, like X and Y, are stored for each vertex of a line. In order to use the Field Calculator to manipulate M values, the vertices must be converted to points, and the M values must be exposed in attribute format. Once the desired modifications have been made, the original routes can be calibrated using the new M values.


The following steps provide a general guideline for exposing, manipulating, and calibrating M values.

Some of the tools used in this workflow require an ArcInfo or ArcGIS for Desktop Advanced license.

  1. Use the Feature Vertices to Points tool to convert the route vertices to points. Depending on which vertices need to be modified, the ALL or BOTH_ENDS option could be used.
    Convert Vertices to Points

    [O-Image] Convert Vertices to Points
  2. If the new M values are to be based on the existing M values, the M value for each point must be exposed as an attribute. Use the Add XY Coordinates tool to do this. This adds a POINT_X, POINT_Y, and POINT_M field to the points file.
    Add XY Coordinates

    [O-Image] Add XY Coordinates

  3. Add a field, and use the Field Calculator to generate the new M values.
    Calculate New Ms

    [O-Image] Calculate New Ms
  4. Use the Calibrate Routes tool to calibrate the routes with the new M values. The Route Identifier Field and Point Identifier field should be the same (respectively), while the Measure Field should be the new field created and calculated in the previous steps.
    Calibrate Routes

    [O-Image] Calibrate Routes

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