Lecture 1 - Introduction Flashcards
*What is geodesy?
The scientific discipline that deals with the measurement and representation of the Earth, including its gravitational field in a 3D time-vaying space. The science for the determination and representation of the figure, shape, and size of the Earth and other celestial bodies along with their external gravity field as a function of time and the determination of the mean of the Earths ellipsoid from parameters observed on and beyond the Earths surface.
What is geomatics?
The discipline of gathering, storing, processing, and delivering of geographic information or spatially referenced information.
*What are the major tasks in geodesy?
Determine the shape of the Earth and its external gravity field and its changes with time
Set up the geodetic coordinate system and maintain the national horizontal geodetic control network and the vertical leveling network
Study the observational methods for geodetic instruments
Describe the mathematical models for the geodetic calculations on the Earth ellipsoidal surface and map projection from ellipsoidal surface to plane.
*What is the problem with point positioning?
Given coordinates of the observed e.t. objects along with measurements of quantities linking a terrestrial point to these objects and must compute coordinates of the point. But how do we determine coordinates of e.t. objects?
Summarize the historic development of geodesy (4 stages).
Stage 1: Spherical Earth Model (17th century) - arc measurement
Stage 2: Ellipsoidal Earth Model (17th-19th) - formation of ellipsoidal geodesy, large scale triangulation, different ellipsoids, gravity measurements, etc.
Stage 3: Concept of Geoid (19th)
Stage 4: Modern Geodesy
What is the technical function of geodesy in modern world?
The essential scientific/technical foundation for all georeference/geospatial/positioning/navigation related disciplines from national infrastructure to space tech. and national defense.
What are the three essential branches of geodesy?
Traditional Geodesy: Geometric (describing locations in terms of geometry) and Physical (determining gravity field and geoid heights)
Modern Geodesy: Space (VLBI and sattelite), Dynamic, Ocean and applied/engineering surveying.
*What are the modes of point positioning?
- Terrestrial coordinate systems: needed for positioning points and objects in Earth’s immediate environment. Spin and revolves with Earth - Earth-fixed.
- Celestial Coordinate systems: needed for sighted stars and extragalactic radio sources. Doesn’t spin with Earth but may revolve with the same velocity as Earth.
- Orbital Coordinate systems: Needed for observed satellites. Doesn’t spin with the Earth but revolves with it on its axis.
*What is dynamical method of defining coordinate systems?
(Traditional approach) Links coordinate systems to orbital characteristics of the Earth around the Sun and to direction of rotation axis of Earth.
Coordinate systems: affected by all irregularities of revolution of Earth about the Sun and its spin about its own axis.
*What is kinematic method of defining coordinate systems?
(Modern approach) Establishes coordinate systems that are as close as possible to inertial by fixing directions of coordinate axis wrt distant matter of the universe (celestial coordinate system) or wrt selected locations on Earth’s surface (terrestrial coordinate system).
*What is point positioning?
Point positioning is the determination of the coordinates of a point on land, at sea, or in space with respect to a coordinate system. Point position is solved by computation from measurements linking the known positions of terrestrial or extraterrestrial points with the unknown terrestrial position. This may involve transformations between or among astronomical and terrestrial coordinate systems.
