Description:
The Guam and Northern
Mariana Islands gravimetric geoid
extends from 11N to 18N and from 143E
to 146E with a spatial resolution of
1'x1'. It is a pure gravimetric geoid
included into the USGG2012 (U.S.
Gravimetric Geoid) model. The geoid
heights are referred to the GRS80
ellipsoid in the IGS08 (epoch 2005.0)
reference frame. The reference global
Earth gravity model is EGM2008, with
the incorporation of GOCE and GRACE
information from the GOCO02S model.
Since EGM2008 accounts for the effects
of the terrain through about 5' (10
km), SRTM 3" (90 m) data were used to
produce a Residual Terrain Model
between 3" and 5', accounting for much
of the high frequency variability seen
in the residual gravity signal. The
remove-restore technique employed for
the geoid determination is basically
the same of the one used for the
previous release (USGG2009), see Wang
et al. (2012), J Geod 86:165-180.
Additional information is available
at: http://www.ngs.noaa.gov/GEOID/.
The one line header contains the
following parameters: - Southernmost
North latitude - Westernmost East
longitude - Distance interval in
latitude - Distance interval in
longitude - Number of rows - Number of
columns - Always equal to one While
the Hybrid Puerto Rico and the Virgin
Islands geoid extends from 11N to 18N
and from 143W to 146W with a spatial
resolution of 1'x1'. It is a hybrid
geoid included into the GEOID12A
model, obtained by fitting the
corresponding USGG2012 model to
GPS-leveling data. The geoid heights
are referred to the GRS80 ellipsoid in
the NAD 83 (epoch 2010.0) reference
frame), which is the official
geometric datum of the U.S. National
Spatial Reference System. The
reference global Earth gravity model
is EGM2008, with the incorporation of
GOCE and GRACE information from the
GOCO02S model. SRTM data were used to
produce a Residual Terrain Model
between 3" and 5', accounting for much
of the high frequency variability seen
in the residual gravity signal.
After detecting some defects in the GPS/levelling used to create GEOID12, GEOID12A was developed as a replacement.
In particular changes impacted regions in the states of Alabama, Mississippi, Louisiana, Texas, Oklahoma, and Wisconsin.
There were also some changes in Canada. However, GEOID12A, as with all previous hybrid geoid models (GEOID09, GEOID03),
should not be used in Canada or Mexico or in ocean areas more than 30 km offshore. The regions outside of the Conterminous
United States were unaffected by these changes, but the name of the model for those regions was changed to GEOID12A for
consistency. GEOID12B is a further replacement of GEOID12A with changes only for the Puerto Rico/U.S. Virgin Islands region
based on a corrected set of GPS/levelling data. In all areas other than the Puerto Rico/U.S. Virgin Islands region, GEOID12B
is identical to GEOID12A.
Additional information is available
at: http://www.ngs.noaa.gov/GEOID/.
References:
D.A. Smith, D.G. Milbert (1999). The
GEOID96 high resolution geoid height
model for the United States. Journal
of Geodesy, 73(5), pp. 219-236. DOI: 10.1007/s001900050239
D.R. Roman, Y.M. Wang, W. Henning, J.
Hamilton (2004). Assessment of the New
National Geoid Height Model - GEOID03.
Surveying and Land Information
Science, 64(3), pp. 153-162.
Y.M. Wang, J. Saleh, X. Li, D.R. Roman
(2012). The U.S. Gravimetric Geoid of
2009 (USGG2009): Model Development and
Evaluation. Journal of Geodesy, 86(3),
pp. 165-180. DOI: 10.1007/s00190-011-0506-7
Web of Science ID:
DRCI:DATA2019017015400495
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