|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
|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.