sg Flashcards
geodesy (36 cards)
What is the classical definition of geodesy according to Helmert?
Geodesy is the science of the measurement and mapping of the Earth’s surface.
What are the main objectives of satellite geodesy?
- Determination of precise global, regional and local three-dimensional positions
- Determination of Earth’s gravity field and linear functions of this field
- Measurement and modeling of geodynamical phenomena
What prerequisites are needed for satellite geodesy?
A comprehensive knowledge of satellite motion and the description of positions of satellites and ground stations in suitable reference frames.
In what domains does satellite geodesy belong?
- Basic sciences
- Applied sciences
- Geosciences
- Engineering sciences
What is the significance of artificial satellites in geodesy?
They provide high orbiting targets visible over large distances, allowing for the establishment of geodetic ties between continents and islands.
Define the geometrical method of satellite geodesy.
It is a method where satellites are regarded as ‘fixed’ control points within large-scale or global three-dimensional networks.
What is the dynamical method of satellite geodesy?
It uses satellites as probes in the gravity field of Earth, observing orbital motion to determine forces acting on them.
What is the difference between short arc and long arc techniques in satellite geodesy?
- Short arc techniques: arcs of a few minutes up to several revolutions around Earth
- Long arc techniques: arcs up to around 30 days and more
What is the main advantage of satellite observations over classical techniques?
Satellite observations refer to the planet Earth as a whole and have a global character.
What historical event marked the beginning of satellite geodesy?
The launch of the first artificial satellite, SPUTNIK-1, on October 4, 1957.
What was one of the first outstanding results in satellite geodesy after 1957?
The determination of Earth’s flattening as f = 1/298.3 from observations of EXPLORER-1 and SPUTNIK-2.
List some significant events in satellite geodesy following the launch of SPUTNIK-1.
- Launch of EXPLORER-1
- Third Zonal Harmonic (Pear Shape of Earth)
- Launch of TRANSIT-1B
- Launch of ECHO-1
- Launch of ANNA-1B
What were the main results achieved by 1964 in satellite geodesy?
- Determination of a precise numerical value of Earth’s flattening
- Determination of the general shape of the global geoid
- Determination of connections between the most important geodetic datums
What characterized the development phase of satellite geodesy from 1958 to around 1970?
Development of basic methods for satellite observations and computation and analysis of satellite orbits.
What advancements were made in satellite geodesy from 1970 to around 1980?
Development and refinement of new observation techniques, particularly laser ranging to satellites and satellite altimetry.
Fill in the blank: The term _______ is used to describe the measurement of gravity intensity.
Gravimetry
True or False: Satellite geodesy is only concerned with artificial satellites.
True
What are the Standard Earth models developed by the Smithsonian Astrophysical Observatory?
SAO SE I to SAO SE III
These models were among the first Earth models published.
What was the primary purpose of the satellite PAGEOS?
Establishment of a purely geometrical and worldwide satellite network
PAGEOS used BC4 cameras for observations.
What new observation techniques were developed between 1970 and 1980?
Laser ranging, satellite altimetry, and geodetic Doppler positioning
These techniques refined global geoid and coordinate determinations.
What were the outcomes of increased accuracy in observations during the 1970-1980 phase?
Measurement of geodynamical phenomena such as Earth rotation and crustal deformation
Doppler surveying was used for geodetic control networks.
What significant satellite system began to replace conventional methods in the 1980-1990 phase?
NAVSTAR Global Positioning System (GPS)
This marked a shift in surveying techniques.
What are the two major international services established in the 1990-2000 phase?
- International Earth Rotation Service (IERS)
- International GPS Service (IGS)
IERS provides Earth orientation parameters; IGS focuses on GPS orbits.
What advancements in satellite geodesy occurred from 2000 onwards?
Launch of gravity field probes, next generation GNSS, and high-resolution radar sensors
Focus on disaster prevention and environmental monitoring.
