The "HTDP" DatumTransform does not have fixed parameters. Instead, it is dynamically created with a call to the DataSource object's ConstructHTDPTransformation() method, or selected from the options provided in a TransformPicker. In order to create a valid transformation, the input and output geodetic coordinate system must be one of the following:
IGb00 Coordinate System
IGS00 Coordinate System
IGS05 Coordinate System
IGS97 Coordinate System
ITRF 00 Coordinate System
ITRF 05 Coordinate System
ITRF 88 Coordinate System
ITRF 89 Coordinate System
ITRF 90 Coordinate System
ITRF 91 Coordinate System
ITRF 92 Coordinate System
ITRF 93 Coordinate System
ITRF 94 Coordinate System
ITRF 96 Coordinate System
ITRF 97 Coordinate System
MARP00 Coordinate System
NAD83(1986)
NAD83(NSRS2007)
NEOS90 Coordinate System
PACP00 Coordinate System
PNEOS90 Coordinate System
SIO_MIT92 Coordinate System
WGS 72
WGS 84
WGS84_G1150 Coordinate System
WGS84_G730 Coordinate System
WGS84_G873 Coordinate System
Additionally, the transform requires an input and output epoch date that is used for all computations. These dates are specified in a decimal year format, and can be easily generated using the TimeUtil class. For more information on how to construct and use an HTDP transformation, please take a look at Lesson 6 in the Getting Started portion of this manual.