Overview of Geodesy: Science and Branches

Overview of Geodesy

• Geodesy is the science focused on measuring and mapping the Earth's surface.
• The term derives from Greek, with "Geo" meaning "Earth" and "Daiein" meaning "to divide."
• Geodesy's main purposes are to determine the Earth's shape, gravity field, and the precise location of points on its surface.

Branches of Geodesy

• Geometric Geodesy: Investigates the size and shape of the Earth using geometric principles, particularly the ellipsoid of revolution.
• Physical Geodesy: Studies the Earth's gravity field to provide a more precise definition of its size and shape.
• Satellite Geodesy: Employs satellite systems like GPS and GLONASS for precise measurements of Earth's geometry and gravity field.
• Geodetic Astronomy (Astro-Geodesy): Uses measurements of celestial bodies to determine positions on Earth.
• Integrated Geodesy: A newer branch that merges geometric and physical geodesy.

Introduction to Satellite Geodesy

• Satellite geodesy utilizes artificial satellites to measure and monitor the Earth’s size, shape, and gravity field.
• Main goals include determining Earth’s figure, measuring the geoid, and studying geodynamic phenomena such as crustal deformation and polar motion.
• Historical milestones include:
  • Sputnik-1 (1957): Marked the dawn of satellite geodesy as the first artificial satellite.
  • Explorer 1 (1958): The first U.S. satellite, significant for discovering the Van Allen radiation belts.
  • GRACE (2002-2017): Monitored Earth's gravity field anomalies and changes in mass distribution.

Methods in Satellite Geodesy

• Geometrical Method:
  • A direct approach that treats satellites as high-altitude targets for positioning.
  • Establishes global 3D networks using satellites as "fixed" control points.
• Dynamical Method:
  • An indirect approach leveraging satellite orbital behavior to infer gravitational effects.
  • Observes orbit deviations caused by gravitational forces to model Earth's gravity field.
• Types of Observation Platforms:
  • Earth to Space Methods: Ground observation of satellites (e.g., GPS).
  • Space to Earth Methods: Space-based instruments observing Earth's surface (e.g., radar altimetry).
  • Space to Space Methods: Tracking one satellite from another (e.g., satellite-to-satellite tracking).

Key Satellites in Geodesy

• Sputnik-1: The inaugural artificial satellite, initiating satellite geodesy.
• GRACE: Twin satellites mapping Earth's gravity field, tracking mass distribution changes linked to water storage.
• GOCE (Gravity Field and Steady-State Ocean Circulation Explorer): High-precision gravity field mapping satellite aiding oceanography and climate studies.
• CHAMP (Challenging Minisatellite Payload): A German satellite focused on atmospheric and geoscientific research, utilizing GPS radio occultation.

Applications of Satellite Geodesy

• Global Geodesy: Establishes global reference frames, defines Earth's ellipsoid, and connects national geodetic datums.
• Geodetic Control: Sets up networks for large-scale surveys and connects remote islands with mainland geodetic frameworks.
• Geodynamics: Monitors crustal movements, tectonic activity, and measures polar motion and Earth's rotation.
• Navigation and Marine Geodesy: Provides precise navigation for vehicles and supports marine mapping and oceanographic research through satellite technology.
• Applied and Plane Geodesy: Used in urban planning, boundary demarcation, GIS applications, and engineering surveys for construction.

Historical Developments in Satellite Geodesy

• 1957-1970: Focused on developing basic methods and establishing satellite orbits.
• 1970-1980: Witnessed advancements in accuracy for geodynamical studies, enabling better understanding of crustal movements and Earth rotation.

This quiz provides an overview of geodesy, including its definition, purpose, and branches. Explore how geometric geodesy contributes to our understanding of the Earth's size and shape through measurement and mapping techniques.