Add/Modify Linear Referencing Methods

You use the Add/Modify Linear Referencing Methods dialog box to define the linear referencing methods you want to use with your linear assets.

A linear referencing method (LRM) is a method of determining a position by using a known start point, a measure, and a direction. To define a linear referencing method, you specify units of measure for the length of the linear asset and for three offset measures (see offset, below). You can define multiple linear referencing methods, but you can apply only one of them to an individual linear asset.

To add a linear referencing method:

  1. From the Select Action menu in the Assets application, select Add/Modify Linear Referencing Methods.

  2. Click New Row.

  3. In the LRM field, enter a name for the linear referencing method. Enter a description in the LRM Description field. To enter additional information, click Long Description .

  1. In the Unit of Measure field, click Select Value to select the unit of measure you want to use for the length of the linear asset, sometimes referred to as the X axis. For example, you might want to measure the length of a road in miles or kilometers.

  2. By default, the Base Unit of Measure field displays the unit you entered in the Unit of Measure field. You can select a different value for the base unit of measure if you want to store measures in both units of measure.

You can only select a different value if a conversion factor between the two units of measure exists. You enter conversion factors using the Unit of Measure and Conversion > Add/Modify Conversions action. The value in the Unit of Measure field is the display value. The value in the Base Unit of Measure field will also be stored in the database. For example, you might want to store measures in kilometers but display them in miles.

  1. In the Offset Unit of Measure field, click Select Value to select the unit of measure for distances from a reference point along the length of the linear asset.

For example, the unit of measure for a linear asset might be miles, but you use feet to measure distances from a reference point, such as 300 feet from Mile Post 12.

  1. Select values for the remaining fields:

Y Offset Unit of Measure.  The Y Offset is a distance perpendicular to the direction of the linear asset. For example, a speed limit sign is located 10 feet from the right edge of the road.

Z Offset Unit of Measure.  The Z Offset is a distance above or below a linear asset. For example, an exit sign is located 18 feet above the surface of the road, and a culvert is 4 feet below the surface of the road.

Y Reference.  The point from which the Y Offset is measured. Click Select Value to select a value. For example, a stop sign is located not just 20 feet from a road, but 20 feet from the midline of a road.

Z Reference.   The point from which the Z Offset is measured. Click Select Value to select a value. For example, an exit sign is located 18 feet above the road surface, or a culvert is 12 feet below the road bed.

  1. Click OK.

To modify a linear referencing method:

  1. From the Select Action menu in the Assets application, select Add/Modify Linear Referencing Methods. The Add/Modify Linear Referencing Methods dialog box opens.

  2. On the row where you want to make a change, click View Details .

  3. Edit fields as needed and click Close Details .

  1. Click OK.

You cannot edit an LRM after you apply it to an asset.