Download Summer of 2013- NOAA National Geodetic Survey Puerto Rico

Puerto Rico Airborne Gravity
Data Modeling
Kevin Brodie II
Norfolk State University, Virginia
Computer Science
Dr. Theresa Damiani (Mentor)
National Geodetic Survey
Resilient Coastal Communities and Economies
5/23/2017
1
Overview
• What is Geodesy?
• Background
• Puerto Rico
• Hypothesis
• Methodology
• Results
• Discussion/Future Work
5/23/2017
2
Geodesy is…
• The science of measuring the size and shape
of the earth, including the gravitational field
and its locations throughout different points in
an area.
Geoid is simply a surface of
equal gravity potential energy.
The Earth’s mass is unequally
distributed causing certain
areas to have a greater
gravitational pull which makes
the geoid seem to have bulges.
5/23/2017
3
Background
•
The Airborne gravity data was collected by the
National Geodetic Survey’s GRAV-D program there
in 2009. GRAV-D surveyed Puerto Rico and the
islands in the marine areas to the north and south,
where the Puerto Rico trench and other ocean
floor features are located.
Atlantic
Caribbean
5/23/2017
4
About Puerto Rico
Different classification schemes exist
for the soils of Puerto Rico.
Five general soil types: humid coastal
plains, semiarid coastal plains, humid
uplands, semiarid uplands, and humid
upland valleys.
The territory is
very mountainous (covering about
60%), except in the regional coasts, but
Puerto Rico offers astonishing variety:
rain forest, deserts, beaches, caves,
oceans and rivers.
5/23/2017
5
Hypothesis
This research project has the
objective of better understanding the
setting and geologic composition of
PRVI, which is important for NOAA’s
use in geodetic modeling of the area.
We hypothesize that using gravity
data files for the 2D modeling of
topography and bathymetry of PRVI,
gravity anomalies, that are produced
from algorithms of code, can be
calculated and graphed in MATLAB.
Finally the created 2D model will have
polygons that are added that mimic
oceanic crust and mantle. These
polygons drastically effect the model’s
gravity and are tweaked in order for
the model gravity to match actual
airborne gravity survey data in 2009.
Then the model that is created is
interpreted in order to better
understand the composition of the
islands.
5/23/2017
6
Methodology
Latitude
5/23/2017
Longitude
Full-field
gravity
(mGal)
Free-air
gravity
(mGal)
7
5/23/2017
8
Topography
Caribbean Bathymetry
Atlantic Bathymetry
5/23/2017
9
This boundary
that separates
two different
densities of
rock is what
gives the
gravity reading
Oceanic
Oceanic
Crust
Crust
density=2.9733
Density = 2.97 g/cm
For each
polygon there is
a calculation
done for each
point separately
to find the
gravity.
Mantle
Mantle
density =3.3
density=3.3
g/cm
A rigorous
process of
editing the
model to
produce a
similar gravity
reading to the
measured
gravity is
done.
5/23/2017
10
Results
 This project was the 1st step in
modeling more complex diagrams
and figures of the PRVI
 The topographic and bathymetric
models of PRVI were created with
MATLAB; along with that, realistic
gravity signals were calculated
using different algorithms.
 Gravity and model results were
consistent among other
researchers work.
 There was a distinct protruding
mass of mantle that was found and
observed.
 Knowing the gravity, sea level can
be located, which in turn improves
the accuracy of elevation
measurements in Puerto Rico
5/23/2017
Caribbean
plate
Atlantic plate
11
Discussion/Future Work
5/23/2017
12
Knowing where the
density changes among
land, gravity can be
calculated
This project was one component of many that leads
to the updating of the vertical datum.
Based off of the gravity
information, Sea level
can be located
Resilient Coastal Communities
and Economies
With actual Sea level
heights known, the
vertical datum can
be updated
With the vertical datum
more accurate, this allows
the coastal communities to
be further prepared for
natural disasters
5/23/2017
13
Images collected by NGS emergency response team of post-Sandy destruction. Houses and roads
washed away by storm surge illustrate the importance of knowing sea level and heights above sea
level. Coastal communities can rebound from storms more quickly, with less damage, if we know
which areas are in the most danger from rising waters during storms
5/23/2017
14
Acknowledgements
• A special thank you to:
- Dr. Theresa Damiani
- National Geodetic Survey
- Office of Education Scholarship Team
- Fellow EPP Scholars
5/23/2017
15