The EGM96 surface was enhanced using local gravity and terrain data to create a regional geoid model (USGG2003). The difference between the enhanced EGM96 surface and that implied by the 14185 GPSBM’s serving as control data are significant. Not all problems are related to a bias difference, significant trends occur along the coasts.
	The question is, which is more correct? Another line of evidence would be need to ascertain this – namely a comparison with the actual sea surface and a modeled mean dynamic topography: GEOID + MDT + MSSH
	Hence comparison of the gravimetric geoid and MDT models at coastal stations (TBM’s) might resolve the datum question in an absolute sense.
	This seems to offer some hope of deriving a seamless and consistent set of gravity across the region. These gravimetric geoid values may be directly compared to the NAVD 88 datum at tidal bench marks to estimate the magnitude of error in NAVD 88 – ASSUMING the derived gravimetric geoid agrees well with the MDT and tide models as well as the observed lidar sea surface heights.