The POINT:UNITS parameter is a single four-character value that records the units of distance measurement used by the 3D data e.g.  mm, cm, m etc.  POINT:UNITS is typically four ASCII characters and may be upper or lower case.  The common value for this parameter is mm (millimeters). 

Note that this parameter only records the units of measurement – it does not control them and is not used in the 3D scaling calculations.  Changing the value of POINT:UNITS from “mm” to “cm” will not re-scale the coordinate system used to generate the 3D data points unless this is a feature that is specifically implemented in your software application.