I'm looking to do datum conversions for points with six degrees of freedom, that is, they are described by a heading, pitch, and roll in addition to their position information.
I know how to convert the orientation vector from a local NED or geodetic frame to the ECEF frame (using the method in this paper), but I don't know how to handle the orientation change when I use helmert transforms to convert between the different datums in ECEF space (i.e. WGS84 to NAD83).
So my question is, how can I perform a 6-DOF helmert transform, which preserves orientation information across the datum transformation? Is orientation affected by the transformation at all?