Hi Caddcop,
The function I was talking about is called Extract TM From STM.
Note that in our latest release some analysis functions that can be done directly on a STM has been added (see the Bentley Descartes SELECTSeries 5 section on http://communities.bentley.com/products/3d_imaging_and_point_cloud_software/w/wiki/6993.bentley-descartes.aspx).
The only drawback of those functions is that the size of the region on which the analysis can be done is limited.
HTH,
Mathieu