Creo Simulate > Reference Links > Datum Points for User-Defined Measures
  
Datum Points for User-Defined Measures
If you plan to place a measure at a specific point on an exterior surface, your part needs to include a datum point at that location unless the location is a vertex. Provided you are working with an assembly, you can place measures on the interior of your model by adding a datum point to a part surface that will merge with a mated part during a run.
Note that for reaction measures, you can use datum points that do not lie on the part geometry. These points can lie buried within the part or lie outside the part.
You can add datum points within Creo Simulate as you define your measures. These datum points are:
only available for your Creo Simulate sessions unless you promote them
not visible on your part or assembly while you are working at the Creo Parametric level unless you promote them
As an alternative, you can add datum points to your model in Creo Parametric before entering Creo Simulate. In this case, the datum points are available for all your Creo Parametric sessions as well.
Return to User-Defined Measures.