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:
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IGb00 Coordinate System
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IGS00 Coordinate System
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IGS05 Coordinate System
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IGS97 Coordinate System
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ITRF 00 Coordinate System
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ITRF 05 Coordinate System
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ITRF 88 Coordinate System
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ITRF 89 Coordinate System
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ITRF 90 Coordinate System
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ITRF 91 Coordinate System
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ITRF 92 Coordinate System
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ITRF 93 Coordinate System
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ITRF 94 Coordinate System
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ITRF 96 Coordinate System
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ITRF 97 Coordinate System
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MARP00 Coordinate System
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NAD83(1986)
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NAD83(NSRS2007)
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NEOS90 Coordinate System
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PACP00 Coordinate System
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PNEOS90 Coordinate System
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SIO_MIT92 Coordinate System
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WGS 72
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WGS 84
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WGS84_G1150 Coordinate System
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WGS84_G730 Coordinate System
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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.