Earth Mapping International (EMI)

Geodesy & Geophysics RESEARCH

OVERVIEW

Geodesy, in the history of science, is one of the oldest disciplines. It has a noble tradition in the development of the classical physical science. Great names like Gauss, Laplace, Bessel, Newton, and Euler have left their mark on science through their studies of geodesy. Geodesy has been used to measure outer shape and inner composition of the earth utilizing gravity and magnetic fields, isostasy, space technology, astronomy, and terrestrial measurements. The shape of earth is defined by the gravity field, which varies from place to place, thus making it an irregular surface. For mapping purposes, the shape of the earth is defined by two different surfaces, such as a horizontal datum, or an ellipsoidal surface, defined by semi-major and minor axes, and a vertical datum; a geoid or an equipotential surface, which is physically represented by a still ocean surface.

Gravity, tide gauge, geodetic, and satellite observational data are integrated and modeled to compute a geoidal surface. After a geoidal surface is determined, then other surveys, like Global Positioning System (GPS) or differential leveling, can be used to measure surface elevations to create topographic maps. Gravity measurements can also be used to determine variations of rock densities (as a geologic mapping tool), and to look for time changes of gravity (for monitoring elevation changes, magma intrusions, or water-table variations), and for metrology laboratories to calibrate weighing machines. Satellite geodesy, with current constellation of three different types of navigational satellite systems (GPS, Russian GLONASS, and European Galileo), can provide millimeter level relative accuracy worldwide in horizontal as well as vertical coordinates XYZ (WGS 84 an ellipsoidal mathematical surface). However, for many applications such as climate change studies (global warming), construction of continental highways/railways, studies of plate tectonics, and impact of global warming on sea level rising, geocentric coordinates and geoidal (equipotential surface) heights are needed.

APPLICATIONS
Some of the pertinent applications of geodesy and geophysical research are in the following areas:

Power & Communications Grids
Water Resources (ground water tables and volume computation)
Dams & Reservoirs- Monitoring and Forecasting
Mining & Natural Resources- Exploration & Extraction
Continental Infrastructure Development (highways, railways, waterways)
Early Warnings of Tsunamis
Monitoring of Plate Tectonics
Early Warnings & Study of Earthquakes
Sea Level Measurements & Monitoring
Isostasy

RESEARCH
Some of the researches performed by EMI’s associates are listed below:

Research was performed on computation of regional and local geoid undulations towards height modernization using satellite and terrestrial gravity data. 61 counties in North Georgia and 4 counties in NW South Carolina were chosen for this research. GPS and terrestrial gravity data was collected on 300+ control points. The terrestrial gravity data was integrated with the Gravity Recovery and Climate Experiment (GRACE) Satellite gravity data for computation of geoid undulation. This project was funded by NASA.
Research was performed on geoid modeling. This paper was published in GPS Navigation Journal.
Research was performed on GPS planning. This paper was published in the ACSM Journal of Surveying and LIS.
Research and planning of a continental GPS geodetic network was designed for Africa, a paper was published in the ISPRS Proceeding.
A First Order Geodetic Network was designed for Yemen; the project was funded by the UNDP Yemen.
A First Order Geodetic Network was designed for Nepal; the project was funded by the Government of Nepal.
High Accuracy Reference Network utilizing GPS was designed for Georgia (GA-HARN), this project was funded by University of Georgia and supported by Surveying and Mapping Society of Georgia, and the National Geodetic Survey.