Portal:Geodesy

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The Geodesy Portal

GPS Block II-F satellite in Earth orbit

Geodesyorgeodeticsis thescienceof measuring and representing thegeometry,gravity,andspatial orientationof theEarthintemporally varying 3D.It is calledplanetary geodesywhen studying otherastronomical bodies,such asplanetsorcircumplanetary systems.Geodesy is anearth scienceas well as a discipline ofapplied mathematics,and many consider the study of Earth's shape and gravity to be central to the science.

Geodynamicalphenomena, includingcrustalmotion,tides,andpolar motion,can be studied by designing global and nationalcontrol networks,applyingspace geodesyand terrestrial geodetic techniques, and relying ondatumsandcoordinate systems.Geodetic job titles includegeodesistandgeodetic surveyor.(Full article...)

Selected images

Image 1Variations in the gravity field of theMoon,fromNASA(fromGeodesy)
Image 2A relative gravimeter (fromGeodesy)
Image 3An artist's rendering of theprotoplanetary disk(fromEarth's rotation)
Image 4Surveyor using atotal station(fromGeomatics)
Image 5Navigationdevice,Apollo program(fromGeodesy)
Image 6Topographic map ofEaster Island(fromCartography)
Image 7On aprogradeplanet like Earth, thestellar dayis shorter than thesolar day.At time 1, the Sun and a certain distant star are both overhead. At time 2, the planet has rotated 360 degrees and the distant star is overhead again but the Sun is not (1→2 = one stellar day). It is not until a little later, at time 3, that the Sun is overhead again (1→3 = one solar day). (fromEarth's rotation)
Image 8The cartographic process (fromCartography)
Image 92D grid for elliptical coordinates (fromGeodesy)
Image 10Plot of latitude versus tangential speed. The dashed line shows theKennedy Space Centerexample. The dot-dash line denotes typical airlinercruise speed.(fromEarth's rotation)
Image 11Visual fix by three bearings plotted on a nautical chart (fromGeopositioning)
Image 12Europa reginainSebastian Münster's "Cosmographia",1570 (fromCartography)
Image 13A medieval depiction of theEcumene(1482, Johannes Schnitzer, engraver), constructed after the coordinates in Ptolemy'sGeographyand using his second map projection. The translation into Latin and dissemination ofGeographyin Europe, in the beginning of the 15th century, marked the rebirth of scientific cartography, after more than a millennium of stagnation. (fromCartography)
Image 14Datum shift betweenNAD27andNAD83,in metres (fromGeodesy)
Image 15Gravity measurement devices, pendulum (left) and absolute gravimeter (right) (fromGeodesy)
Image 16Principles of geolocation using GPS (fromGeopositioning)
Image 17Ellipsoid- a mathematical representation of theEarth.When mapping in geodetic coordinates, a latitude circle forms a truncated cone. (fromGeodesy)
Image 18Starry circles arc around the south celestial pole, seen overhead atESO'sLa Silla Observatory.(fromEarth's rotation)
Image 19TheBedolina Mapand its tracing, 6th–4th century BCE (fromCartography)
Image 20A modern instrument for geodeticmeasurementsusingsatellites(fromGeodesy)
Image 21Geodetic control mark (fromGeodesy)
Image 22Illustrated map (fromCartography)
Image 23Equatorial ( $a$ ), polar ( $b$ ) and mean Earth radii as defined in the 1984World Geodetic System(fromGeodesy)
Image 24Gravity at different internal layers of Earth (1 = continental crust, 2 = oceanic crust, 3 = upper mantle, 4 = lower mantle, 5+6 = core, A = crust-mantle boundary) (fromGravity of Earth)
Image 25A 14th-centuryByzantinemap of the British Isles from a manuscript ofPtolemy'sGeography,using Greek numerals for itsgraticule:52–63°N of theequatorand 6–33°E from Ptolemy'sPrime Meridianat theFortunate Isles.(fromCartography)
Image 26A simulated history of Earth's day length, depicting a resonant-stabilizing event throughout the Precambrian era (fromEarth's rotation)
Image 27Copy (1472) ofSt. Isidore's TO mapof the world. (fromCartography)
Image 28Relief mapSierra Nevada(fromCartography)
Image 29Valcamonica rock art(I), Paspardo r. 29, topographic composition, 4th millennium BCE (fromCartography)
Image 30Global plate tectonic movement using GPS (fromGeodesy)
Image 31Earth's gravity measured by NASAGRACEmission, showing deviations from thetheoretical gravityof an idealized, smooth Earth, the so-calledEarth ellipsoid.Red shows the areas where gravity is stronger than the smooth, standard value, and blue reveals areas where gravity is weaker (Animated version). (fromGravity of Earth)
Image 32Height measurement using satellite altimetry (fromGeodesy)
Image 33TheTabula Rogeriana,drawn byMuhammad al-IdrisiforRoger II of Sicilyin 1154. South is at the top. (fromCartography)
Image 34Globalgravity anomalyanimation over oceans from the NASA's GRACE (Gravity Recovery and Climate Experiment) (fromGeodesy)
Image 35Initial acquisition of GPS signal in 2D (fromGeodesy)
Image 36Earth'saxial tiltis about 23.4°. It oscillates between 22.1° and 24.5° on a 41,000-year cycle and is currently decreasing. (fromEarth's rotation)
Image 37Geoid,an approximation for the shape of theEarth;shown here withvertical exaggeration(10000 vertical scaling factor). (fromGeodesy)
Image 38Axial tilt (orObliquity), rotation axis, plane oforbit,celestial equatorandecliptic.Earthis shown as viewed from theSun;the orbit direction is counter-clockwise (to the left). (fromGeodesy)
Image 39Deviation of day length from SI-based day (fromEarth's rotation)
Image 40AMunicharchive withlithographyplates of maps ofBavaria(fromGeodesy)
Image 41Mapping can be done withGPSandlaser rangefinderdirectly in the field. Image shows mapping of forest structure (position of trees, dead wood and canopy). (fromCartography)
Image 42A plumb bob determines the local vertical direction (fromGravity of Earth)
Image 43Howvery-long-baseline interferometry(VLBI) works (fromGeodesy)
Image 44Thislong-exposure photoof thenorthern night skyabove theNepali Himalayasshows theapparent pathsof the stars as Earth rotates. (fromEarth's rotation)
Image 45A map of recent volcanic activity and ridge spreading. The areas where NASA GRACE measured gravity to be stronger than the theoretical gravity have a strong correlation with the positions of the volcanic activity and ridge spreading. (fromGravity of Earth)
Image 46Small section of an orienteering map (fromCartography)
Image 47Earth's rotation imaged byDeep Space Climate Observatory,showing axistilt (fromEarth's rotation)
Image 48A pre-Mercator nautical chart of 1571, from Portuguese cartographerFernão Vaz Dourado(c. 1520– c. 1580). It belongs to the so-calledplane chartmodel, where observed latitudes and magnetic directions are plotted directly into the plane, with a constant scale, as if the Earth were a plane (Portuguese National Archives of Torre do Tombo, Lisbon). (fromCartography)
Image 49GPSBlock IIA satellite orbits over theEarth.(fromGeodesy)
Image 50The definition of latitude (φ) and longitude (λ) on an ellipsoid of revolution (or spheroid). The graticule spacing is 10 degrees. The latitude is defined as the angle between the normal to the ellipsoid and the equatorial plane. (fromGeodesy)
Image 51Areal distortion caused byMercator projection(fromCartography)

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v t e Geodesy
Overview	History Geodesists
Subfields	Cartography Computer cartography Web mapping Earth's orbit Geodetic astronomy Geomatics Gravity of Earth Navigation Photogrammetry Remote Sensing Geopositioning Virtual globe
Physical phenomena	Chandler wobble Coriolis effect Earth's energy budget Earth's gravity field Geodynamo Gravity of Earth Plate tectonics Precession of the equinoxes Tide
Related disciplines	Astronomy Geology Geophysics Mathematics Physics
Geodesy portal Category Commons