Podcast
Questions and Answers
Geodesy is the science of accurately ______ and understanding three fundamental properties of the Earth.
Geodesy is the science of accurately ______ and understanding three fundamental properties of the Earth.
measuring
Geodesy's etymology comes from two Greek words, GEO meaning ______ and DAIESTHAI meaning TO DIVIDE.
Geodesy's etymology comes from two Greek words, GEO meaning ______ and DAIESTHAI meaning TO DIVIDE.
EARTH
When measuring positions and relations between points on the Earth's surface, we are subject to various ______ influences.
When measuring positions and relations between points on the Earth's surface, we are subject to various ______ influences.
physical
The measurement of height above ______ by triangulation or spirit leveling is an application of geodesy.
The measurement of height above ______ by triangulation or spirit leveling is an application of geodesy.
Observations of the direction of ______ by astronomical observations for latitude and longitude are used in geodesy.
Observations of the direction of ______ by astronomical observations for latitude and longitude are used in geodesy.
Isaac Newton formulated gravitational theory after watching an apple fall and questioning why the apple fell straight down rather than ______.
Isaac Newton formulated gravitational theory after watching an apple fall and questioning why the apple fell straight down rather than ______.
The ______ is the equipotential surface of the Earth's gravity field that coincides with mean sea level at rest.
The ______ is the equipotential surface of the Earth's gravity field that coincides with mean sea level at rest.
The difference between the Geoid and mean ______ is an important aspect studied in geodesy.
The difference between the Geoid and mean ______ is an important aspect studied in geodesy.
The geoid approximates mean ______ level.
The geoid approximates mean ______ level.
The shape of the ______ was calculated based on the hypothetical equipotential gravitational surface.
The shape of the ______ was calculated based on the hypothetical equipotential gravitational surface.
Even the most mathematically sophisticated geoid can only ______ the real shape of the earth.
Even the most mathematically sophisticated geoid can only ______ the real shape of the earth.
Since gravity contains information on the subsurface density structure, ______ is a standard tool in the oil and gas industry.
Since gravity contains information on the subsurface density structure, ______ is a standard tool in the oil and gas industry.
Gravimetry is used to localize salt domes or ______ in layers.
Gravimetry is used to localize salt domes or ______ in layers.
The ______ surface is the surface that we see and walk on.
The ______ surface is the surface that we see and walk on.
The ______ surface is related to the gravitational field of the Earth and also known as the mean sea level.
The ______ surface is related to the gravitational field of the Earth and also known as the mean sea level.
The ellipsoidal surface is a mathematical surface, often used for GPS and other ______ measurements.
The ellipsoidal surface is a mathematical surface, often used for GPS and other ______ measurements.
Physical geodesy uses the ______ as a primary model for the Earth's shape.
Physical geodesy uses the ______ as a primary model for the Earth's shape.
An ______ of revolution is used as a representation of Earth's shape and size when more accuracy is required.
An ______ of revolution is used as a representation of Earth's shape and size when more accuracy is required.
If the oceans were at rest, the ocean surface would coincide with the ______.
If the oceans were at rest, the ocean surface would coincide with the ______.
The difference between the ocean surface and the geoid is called sea surface ______.
The difference between the ocean surface and the geoid is called sea surface ______.
The Earth's ______ field reflects the internal mass distribution.
The Earth's ______ field reflects the internal mass distribution.
Gravity field knowledge is used together with seismic and other ______ to recover mass distribution.
Gravity field knowledge is used together with seismic and other ______ to recover mass distribution.
The Earth's ______ field can deviate by up to 1m from the geoid.
The Earth's ______ field can deviate by up to 1m from the geoid.
An ellipsoid is symmetrical about three mutually ______ axes.
An ellipsoid is symmetrical about three mutually ______ axes.
Gravity is the invisible force by which a planet or other body draws objects toward its ______.
Gravity is the invisible force by which a planet or other body draws objects toward its ______.
The geoid is the equipotential surface of the Earth at the mean ______.
The geoid is the equipotential surface of the Earth at the mean ______.
The force of gravity keeps all the planets in ______ around the sun.
The force of gravity keeps all the planets in ______ around the sun.
If an object is nearby, it is pulled into the ______.
If an object is nearby, it is pulled into the ______.
Earth's gravity comes from all its ______.
Earth's gravity comes from all its ______.
The radius at the equator is larger than at the ______.
The radius at the equator is larger than at the ______.
Mountains have more mass than a ______, thus affecting local gravity.
Mountains have more mass than a ______, thus affecting local gravity.
Physical geodesy is the branch of geodesy that studies the physical properties of the Earth's ______ field.
Physical geodesy is the branch of geodesy that studies the physical properties of the Earth's ______ field.
Physical Geodesy utilizes measurements and characteristics of the Earth’s ______ field.
Physical Geodesy utilizes measurements and characteristics of the Earth’s ______ field.
Minute changes in the gravity field overtime can be attributed to changes in ______ parameters.
Minute changes in the gravity field overtime can be attributed to changes in ______ parameters.
With precise satellite techniques, ______ is one of the main aims of spaceborne gravimetry.
With precise satellite techniques, ______ is one of the main aims of spaceborne gravimetry.
To gain knowledge about the subsurface structure, gravimetry is a valuable tool for certain ______ engineering projects.
To gain knowledge about the subsurface structure, gravimetry is a valuable tool for certain ______ engineering projects.
The behavior of the Earth’s ice masses is a critical indicator of global climate change and global ______ behavior.
The behavior of the Earth’s ice masses is a critical indicator of global climate change and global ______ behavior.
Monitoring the melting of the Greenland and Antarctica ice caps is an important ______ issue.
Monitoring the melting of the Greenland and Antarctica ice caps is an important ______ issue.
Determining the depth-to-bedrock is important for the layout of a ______.
Determining the depth-to-bedrock is important for the layout of a ______.
The results of satellite gravity missions may be used to constrain basin-scale ______ parameters.
The results of satellite gravity missions may be used to constrain basin-scale ______ parameters.
Flashcards
Ellipsoid
Ellipsoid
A smooth, closed surface where all cross-sections are ellipses or circles. It's symmetric around three perpendicular axes that meet at its center.
Geoid
Geoid
The imaginary surface that represents the Earth's mean sea level if there were no waves, currents, or tides.
Sea Surface Topography
Sea Surface Topography
The difference between the actual sea surface and the theoretical geoid, caused by ocean currents and other factors.
Physical Geodesy
Physical Geodesy
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Earth's Gravity Field
Earth's Gravity Field
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Ellipsoid of Revolution
Ellipsoid of Revolution
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Geophysics
Geophysics
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Gravity Field Knowledge
Gravity Field Knowledge
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Gravity
Gravity
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Orbit
Orbit
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Gravitation
Gravitation
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Geodesy
Geodesy
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Earth's Oblate Shape
Earth's Oblate Shape
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Gravity Anomalies
Gravity Anomalies
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What is Geodesy?
What is Geodesy?
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Triangulation
Triangulation
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Trilateration
Trilateration
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Geoid undulation
Geoid undulation
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Polar motion
Polar motion
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Hydrology
Hydrology
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Hydrological Variations
Hydrological Variations
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Glaciology
Glaciology
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Sea Level
Sea Level
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Oceanography
Oceanography
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Geotechnical Engineering
Geotechnical Engineering
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Heights and Surfaces
Heights and Surfaces
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Ellipsoidal Surface
Ellipsoidal Surface
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Earth Surface
Earth Surface
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Gravimetry
Gravimetry
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Orthometric Height (H)
Orthometric Height (H)
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Salt Dome
Salt Dome
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Fractures
Fractures
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Seismic Profiling
Seismic Profiling
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Study Notes
Geodesy
- Geodesy is the science of accurately measuring and understanding fundamental Earth properties: shape, orientation in space, and gravity field, along with their temporal changes.
- It has Greek roots, combining "geo" (Earth) and "daiesthai" (to divide).
Applications of Geodesy
- Primary or zero order triangulations, trilaterations, and traverses.
- Measuring heights above sea level through triangulation or spirit leveling.
- Astronomical observations of latitude, longitude, and azimuth for survey origin and direction control.
- Crustal movement detection (changes in ground positions and heights).
- Gravity direction observations via astronomical tools for latitude and longitude.
- Gravity intensity observations using pendulums and other instruments.
- Determining Earth's sea-level equipotential surfaces at various heights.
- Studying polar motion.
- Observing Earth tides.
- Measuring the separation between the geoid and mean sea level.
Physical Geodesy
- Physical geodesy studies Earth's gravity field and geopotential, applying its knowledge to geodesy.
- It utilizes Earth's gravity field characteristics to determine the geoid's shape and Earth's size along with arc measurements.
What is the Geoid?
- The geoid approximates mean sea level. It's an equipotential surface of Earth's gravitational field (the gravity field).
- It's not a perfect sphere due to Earth's irregular mass distribution (mountains, valleys, etc)
- Variations from a perfect sphere are small enough that geoid calculations are sufficient for practical applications.
Heights and Surfaces
- Earth Surface: The physical surface we interact with.
- Geoid Surface: Represents mean sea level (no tides, waves, ocean currents).
- Ellipsoidal Surface: A mathematical representation of Earth's best-fit ellipsoid. It's often used in GPS calculations.
Gravity
- Isaac Newton's law of gravity states that every particle attracts every other particle with a force directly proportional to the product of their masses and inversely proportional to the square of the distance between their centers. This force acts on any mass and objects fall toward Earth's center
- Anything with mass has gravity.
- Gravity strength is greater with more mass and closer proximity.
- Earth's gravity comes from its total mass.
Physical Influences
- Measurements on Earth's surface are affected by various environmental influences (e.g., refraction, atmospheric pressure)
- Physical laws govern instruments used, so understanding these laws is important to interpret measurements correctly..
Other Topics
- Geotechnical Engineering: Gravimetry is used for subsurface structure studies for projects like tunnels or nuclear power plants.
- Glaciology & Sea Levels: Earth's ice masses (e.g., Greenland, Antarctica) are crucial indicators of global climate change and sea-level fluctuations. Monitoring their melting is important.
- Geophysical Prospecting: Gravimetry helps to locate resources like minerals and to evaluate subsurface structure (used in the oil and gas industry).
- Orthometric height: vertical distance along the plumb line(a line extending from a given point toward the center of the Earth) from a point to the geoid.
- Geoid height: vertical distance between a point on Earth's surface and the geoid.
- Ellipsoidal height: vertical distance between a point on Earth's surface and the ellipsoid.
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Description
Explore the fascinating science of geodesy, focusing on how we measure and understand Earth's shape, orientation, and gravity. This quiz covers applications ranging from triangulation to crustal movement detection and the study of Earth tides. Perfect for those interested in the fundamentals of geodesy and its practical applications.
