Section Dimensions Don't Match the Model!!

If you ever model curved or circular structures with AutoCAD Arch. | MEP and have started your company template with the OTB Arch. or MEP template you may run into this issue.  Below I have modeled a circular concrete tank and then cut a Section right through the center of the tank.  As you can see the inner diameter of the tank is 100'-0" but when I measure the Section it measures 99'-11_1/16".  This is NO GOOD!!

After the jump see how to fix this issue...

The solution is to adjust the "AEC Display Resolution" setting in Options.

By default, "Facet Deviation" and "Facet Maximum" are set to 1/2" and 128, respectively.  For a little more depth on what Facet Deviation is:

Facet Deviation: the maximum number of facets that can be used to display a curved object, such as a cylinder Mass Element or a curved Wall. The values you specify apply to the current drawing.

The number you specify for Facet Deviation defines the maximum distance from the chord to the arc, the chord being an edge that is created from faceting the curve to the true mathematical arc. Facet Deviation must be greater than zero (0) and has no upper limit.

To resolve our problem we need to turn DOWN Facet Deviation and turn UP Facet Maximum.  My recommendation:

• Facet Deviation to 1/1000"
• Facet Maximum to 10,000.

[Note: Facet Deviation will read 0" after entering 1/1000" due to the drawings "Precision" settings in the UNITS dialog.  You can set the Units to "Engineering" and adjust the Precession way down to see the value show correctly.]

Now go back to your model and refresh the Section.  Once done, it should dimension correctly!!  :)

 Thanks, and I hope this helps...