#### The Priority Surface, Pierce Point, and Drop Point Columns

This area of the dialog box contains these three columns:

1.) Priority Surface

2.) Pierce Point

3.) Drop Point

A "T-value" is the distance of the measured hit from the nominal point along the nominal CAD surface vector. | They display the relevant nominal point values and their T-values (the value displayed to the left of the X, Y, and Z values in parentheses). Priority Surface column – This column lists the surfaces that you have stored as priority surfaces in the Edit CAD Elements dialog box (Edit | Graphics Display Window | Cad Elements).

It displays the type of surface and a check box. The check box allows you to add or remove the surface from the list of priority surfaces maintained by PC-DMIS. If you select the check box, PC-DMIS adds the surface to the priority list. Deselecting the check box removes the surface from the list.

Pierce Point column – This column lists the nominal point values found using PC-DMIS's Pierce Point operation. If you see the text "Failed OP" in this column it means that the pierce point operation failed to find the nominal point on that surface. If PC-DMIS highlights a point in green, then that point is the best nominal point found by the selection algorithm. You can of course override this selected point.

Drop Point column – This column lists the nominal point values found using PC-DMIS's Drop Point operation.