a comparison of continuation models for optimal transformation of gravimetric data
DESCRIPTION
A Comparison of Continuation Models for Optimal Transformation of Gravimetric Data. By: Joanelle Baptiste Elizabeth City State University, NC Supervisor: Dr. Daniel Roman 8/6/04. Line Office (Overview). NOAA Ocean Service (NOS) National Geodetic Survey (NGS) - PowerPoint PPT PresentationTRANSCRIPT
A Comparison of Continuation Models for Optimal
Transformation of Gravimetric Data
By: Joanelle BaptisteElizabeth City State University, NC
Supervisor: Dr. Daniel Roman8/6/04
Line Office (Overview)
NOAA Ocean Service (NOS)
National Geodetic Survey (NGS)
Geosciences Research Division (GRD)
Terms to be familiar with
• Ellipsoid• Geoid• Gravimetric• Gravity anomaly: Δg = gobs-γ• Mean Sea Level
Models of the Earth
Figure of the Earth
OCEAN
Earth’s
Surface
“Ellipsoid”
Geopotential Surface
Geopotential Surface
Geopotential Surface
“Geoid”
P
Q
h
N
Geoid height N = h – HGravity anomaly Δg = gP0 – γQ
P0
plumb lineEllipsoid height, h = distance along ellipsoid normal (Q to P)
Orthometric height, H = distance along plumb line (P0 to P)
Geoid height, N = distance along ellipsoid normal (Q to P0)
P, Q and P0 all have the same lat, lon values.
H
∟
∟
Planar Approach
Earth’s curved surface
flat plane of the model space
Findings: predicted less actual
Height1km
Min.-0.8
Max.0.9
Ave.0.0
St. Dev.0.1
2km -1.7 1.6 -0.2 0.23km -2.8 2.2 -0.5 0.24km -3.9 2.5 -0.9 0.35km -5.2 2.4 -1.5 0.46km -6.3 2.3 -2.3 0.47km -7.7 1.8 -3.2 0.58km -9.1 1.1 -4.2 0.59km -10.6 0.4 -5.4 0.6
10km -12.2 -0.8 -6.7 0.6
Standard Deviation
0.00.20.40.60.8
1 2 3 4 5 6 7 8 9 10
Elevation(km)
Cha
nge
in
Nor
mal
Gra
vity
(m
gals
)
Series1
Minimum(blue), Maximum(lavendar), and Average (yellow) Differences
-15.0-10.0
-5.00.05.0
Elevation (km)
Cha
nge
in
Nor
mal
G
ravi
ty
(mga
ls)
Minimum ValueMaximum ValueAverage Value
Residual Values 1 km 8 km
Conclusion
• The planar method can be used to upward (or downward) continue data with some controls
• Because of systematic effects (ringing), a region for continuation larger than actually desired should be used (add about 0.5 degrees to latitude/longitude limits)
• Systematic average must also be accounted for and may be data dependent (i.e., a bias is introduced)
Importance of this Research
• Supervisor/field assignment• Operational applications
- Engineering- Navigational aid- Storm surge
- Coastal flooding
Accomplishments via EPP
Contributions:
Participant
NOAA
Acknowledgements• NOAA EPP staff• Dr. Daniel Roman• Mr. Edward Allen• Mr. Eric Linzey• Ms. Sonita Tiwari• Ms. Lucy Hall• Ms. Laura Cutrer • Class of 2004 (all my love)
Questions?
The End