Use the Dimension Along custom command to define or apply a constraint on the position of bspline curved objects (for example, hull seams and stiffeners) a given distance above or below other objects. This command helps in designing seams and profiles on a shell or other curved surfaces.
For example, when you place a longitudinal seam a certain distance above a deck, the girth dimension will be constant along the two bspline curves in some cases, while other cases will require a varying girth dimension. The Dimension Along command can also be used to define radicallyplaced stiffeners on either a flat plate or a conicalruled surface.
Add the Dimension Along Command to Your Toolbar
Follow the steps below to add the custom Dimension Along command.

Click Tools > Customize.

On the Toolbars tab, select Dimension.

Select and drag the Dimension Along icon to a place on your toolbar.
Place a Dimension Along a Curve
Follow the steps below to use the Dimension Along command to measure or dimension a bspline curve. The position of the controlled curve is modified if the dimension value is changed.
The curve you are dimensioning must be a bspline curve.

On the vertical toolbar, click Curve and draw the curve you want to measure.
or
Select the curve you want to measure.

Click Point on the vertical toolbar and place your two key points on the curve where you want the dimensioning to start and end.

A key point can be an intersection, end point, midpoint, or center point.

You can also dimension using the intersection of an object with a curve as a key point.
The figure below shows a bspline curve with two points, one placed directly on the curve and one away from the curve. The points are using the Normal (Arrow Backward) style.


Click Dimension Along and select the curve you want to dimension.

Click the first or starting point of the dimension, then click on the ending point of the dimension.
The system displays the dimension measurement for the curve between the two selected points.
The arc above the measurement ( ) indicates that the dimension represents a curved dimension as shown in the figure above.