gravity, geoids, and other vertical datums in the puerto rico/virgin islands region
DESCRIPTION
Gravity, Geoids, and Other Vertical Datums in the Puerto Rico/Virgin Islands Region. Dr. Daniel R. Roman and Dr. Yan Ming Wang. Geodetic Ellipsoidal Height and/or Datum (h) Geodetic or Orthometric Height and/or Datum (H) Geoid Height (N) h = H + N - PowerPoint PPT PresentationTRANSCRIPT
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Gravity, Geoids, and Other Vertical Datums
in the Puerto Rico/Virgin Islands
Region
Dr. Daniel R. Roman
and Dr. Yan Ming Wang
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Significant Concepts & TermsGeodetic• Ellipsoidal Height and/or
Datum (h)• Geodetic or Orthometric
Height and/or Datum (H)• Geoid Height (N)• h = H + N• The geoid and gravity
anomalies are related mathematically:
Oceanographic• Global Mean Sea Level
(MSL)• Local MSL (LMSL) or
Local Mean Tide• Mean Dynamic
Topography (MDT)• MSL + MDT = LMSL• MSL => Geodetic Datum• LMSL => Local Vertical
Datum
T
N R
T
r
Tg
2
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OCEAN Earth
’s
Surfa
ce
“Ellipsoid”
Geopotential Surface
Geopotential Surface
Geopotential Surface
“Geoid”
“P”
“Q”
h
N
h = H + NΔg = gP - γQ
“P”0
H
Normal to geoid
Normal toellipsoid
Deflection of Vertical
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MSL
LMSL
MDT
ellipsoid
geoid
tide station/datum point
MSL + MDT = LMSL
N local geodetic datum
predicted storm surge reachactual storm
surge reach
unexpected area of storm surge
bias
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From the National Geospatial-Intelligence Agency Website at:http://cddis.gsfc.nasa.gov/926/egm96/egm96.html
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Statistical Comparison Between Available Geoid Height Models and 13-Point GPS on BM Profile Along NW Puerto Rico Shoreline
Geoid Height Model
Average (m) St. Dev. (m)
GEOID99 2.34 0.04
CARIB97 2.53 0.04
EGM96 2.07 0.73
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No Biases Removed from GEOID99, CARIB97, or EGM96 Differences with GPSBM's
0.00
0.50
1.00
1.50
2.00
2.50
3.00
3.50
1 2 3 4 5 6 7 8 9 10 11 12 13
GPS on BM station
Res
idu
al G
eoid
Hei
gh
t (m
)
GEOID99 CARIB97 EGM96
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Biases Removed for GEOID99 (2.34 m), CARIB97 (2.53 m), and EGM96 (2.07 m)
-1.00
-0.80
-0.60
-0.40
-0.20
0.00
0.20
0.40
0.60
0.80
1.00
1 2 3 4 5 6 7 8 9 10 11 12 13
GPS on BM station
(Rel
ativ
e) R
esid
ual
Geo
id H
eig
ht
(m)
GEOID99 CARIB97 EGM96
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SRTM 30 m SRTM 90 m NED 1 arcsecond
Available Elevation Data Sets
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Conclusions
• Tidal and Geodetic datums are related
• Additional gravity data are required
• Geoid modeling is best constrained with additional oceanic gravity observations
• Some limited terrestrial observations will help fill in gapped regions but also help to eliminate any datum problems
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Outlook
• Improved terrain models already exist to help model the shortest wavelengths
• Simultaneous lidar observations would help to model the local sea surface and any implied datum shifts
• Impending satellite gravity missions aid in resolving global mean sea level
• A future gravimetric geoid can be generated that will cover CONUS & PR/VI