Sketcher > Dimensioning Sketcher Geometry > Working with Dimension Tools > Normal Dimensions > Dimensioning Splines > To Create Spline Linear Dimensions
  
To Create Spline Linear Dimensions
1. Click Sketch > Normal or right-click in the Sketcher window and choose Dimension from the shortcut menu.
2. Click the spline endpoint.
3. Click the geometry to which you want to dimension.
4. Click the middle mouse button to place the dimension.