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How to get Global values to match ITRF08 epoch 2005

Question asked by Michael Carlson on Apr 25, 2019



I am using the ITRF to NAD83 (2011) coordinate system in TBC for CA, Zone 6.  This has a 7 parameter datum transformation that looks consistent with the Datum Transformation guidance provided by NGS between IGS08/ITRF08 (2005 epoch) and NAD83 2011 2010 epoch.  However, when I import a OPUS position or NGS data sheet point (both having NAD83 (2011) 2010 epoch local coordinates) into TBC, I can't get the "Global" coordinate value to match the values I get using the NGS HDTP tool.  I use this tool by entering in the NAD83(2011) 2010 epoch values and then set the tool to output IGS08/ITRF2008 2005 epoch coordinates that I would check against the "Global" values in TBC for the points of interest.  Is this because velocities are factored into HDTP outputs (i.e., it uses 14 parameters to factor in time and velocity), while TBC's 7 parameter assumes "fixed" or static position?