Once you have measured the eight surface points in "Step 3: Measure Features for Datum A", you can construct DATUM A from those points.
To construct DATUM A:
Execute the measurement routine up to this point to measure the eight surface points. To do this:
From the Edit
Window toolbar (View | Toolbars | Edit Window),
select Clear Marked 
.
This is done so that the manual alignment point (PNT1) is not included
when you select Mark All.
Select Mark
All 
.
When the "Ok to mark manual alignment features?" message appears, click NO.
Select Execute
. PC-DMIS measures
the eight surface points.
From within the Edit Window, ensure that the LAST line in the measurement routine is highlighted.
Select the Insert | Feature
|Constructed | Plane menu item or the Constructed
Plane button 
from the Constructed Features toolbar (View | Toolbars | Constructed Features). The Construct Plane dialog box appears.
Select the 
Best Fit option.
From the feature list, highlight the eight surface points measured in "Step 3: Measure Features for Datum A". In this example, the points are PNT2 through PNT9.
Type DATUM A in the ID box.
Click Create, and then click Close to add the plane feature to the measurement routine.