
	Where results make sense

Topic: Geodetic datum

Related Topics

Omne Datum Optimum

geodetic datum

geodectic datum

geographic datum

In the News (Mon 28 Dec 09)

Northern Trust

Marvin Harrison

Peter Chernin

Gary Locke

Match Play

Penelope Cruz

Mickey Rourke

AR Rahman

Danny Boyle

Hugh Jackman

	World Geodetic System - Wikipedia, the free encyclopedia
		As a result, the elevations in the datums are referenced to the geoid, a surface that is not readily found using satellite geodesy.
		(The datums are relatively oriented with respect to different portions of the geoid by the astro-geodetic methods already described.) The sole contribution of satellite data to the development of WGS 60 was a value for the ellipsoid flattening which was obtained from the nodal motion of a satellite.
		In January 1966, a World Geodetic System Committee composed of representatives from the Army, Navy and Air Force, was charged with the responsibility of developing an improved WGS needed to satisfy mapping, charting and geodetic requirements.
	en.wikipedia.org /wiki/World_Geodetic_System (1839 words)

	Datum - Wikpedia (Site not responding. Last check: 2007-10-02)
		In surveying and geodesy, a datum is a reference point or surface against which position measurements are made, and an associated model of the shape of the earth for computing positions.
		Horizontal datums are used for describing a point on the earth's surface, in latitude and longitude or another coordinate system.
		Vertical datums are either tidal, based on sea levels, or geodetic, based on the same ellipsoid models of the earth used for computing horizontal datums.
	www.bostoncoop.net /~tpryor/wiki/index.php?title=Datum (406 words)

	org.opengis.referencing.datum (GeoAPI 2.1 alpha) (Site not responding. Last check: 2007-10-02)
		A geodetic datum is used with three-dimensional or horizontal (two-dimensional) coordinate reference systems, and requires an ellipsoid definition and a prime meridian definition.
		In that case the vertical datum type is not barometric, but is the same as that of the vertical control network used to obtain the heights of the new points and its vertical datum type.
		The origin of the datum is in that case the (hypothetical) zero atmospheric pressure and the positive vertical axis points down (to increasing pressure).
	geoapi.sourceforge.net /snapshot/javadoc/org/opengis/referencing/datum/package-summary.html (1348 words)

	UNESCO Training Module on GIS - Module C-2 (Site not responding. Last check: 2007-10-02)
		A geodetic datum is a simplified mathematical representation of the size and shape of the earth.
		Geodetic datums define the size and shape of the earth and the origin and orientation of the coordinate systems used to map the earth.
		Geodetic datums and the coordinate reference systems based on them were developed to describe geographic positions for surveying, mapping, and navigation.
	ioc.unesco.org /oceanteacher/resourcekit/Module2/GIS/Module/Module_c/module_c2.html (1297 words)

	ipedia.com: Geodesy Article (Site not responding. Last check: 2007-10-02)
		Geodesy, also called geodetics, is the scientific discipline that deals with the measurement and representation of the earth, its gravitational field and geodynamic phenomena (polar motion, earth tides, and crustal motion) in three-dimensional time varying space.
		Before the satellite geodesy era, the co-ordinate systems associated with geodetic datums attempted to be be geocentric, but their origins differed from the geocentre by hundreds of metres, due to regional deviations in the direction of the plumbline (vertical).
		Because geodetic point co-ordinates (and heights) are always obtained in a system that has been constructed itself using real observations, we have to introduce the concept of a geodetic datum: a physical realization of a co-ordinate system used for describing point locations.
	www.ipedia.com /geodesy.html (2087 words)

	[No title]
		This geodetic reference surface; sometimes called spheroid; was the shape of earth during second era of geodesy, initiated by Isaac Newton in the 17th century (1670).
		The datum was derived for surveys from a general adjustment of the first-order leveling nets of both the United States and Canada.
		Because there are many variables affecting sea level, and because the geodetic datum represents a best fit over a broad area, the relationship between the geodetic datum and local mean sea level is not consistent from one location to another in either time or space.
	www.accd.edu /sac/earthsci/rudnicki/2170/g2170geodesytrm.htm (2428 words)

	Unit 015 - The Shape of the Earth
		Geodetic datums define the reference systems that describe the size and shape of the earth, and the origin and orientation of the coordinate systems used to map the earth.
		Some geodetic datums are based on ellipsoids that touch the surface of the earth at a defined point.
		Plane and geodetic surveying uses the idea of a plane perpendicular to the gravity surface of the earth, the direction perpendicular to a plumb bob pointing toward the center of mass of the earth.
	www.ncgia.ucsb.edu /education/curricula/giscc/units/u015/u015.html (1884 words)

	Imaging Notes - Eye on Quality- November / December 1999 (Site not responding. Last check: 2007-10-02)
		The subject of geodetic datums is perhaps the most misunderstood and confusing issue in the mapping community.
		Geodetic datums provide the means for tying together different map sources, global positioning system (GPS) positioning and navigation, studying Earth tectonics and building a GIS.
		In short, the geodetic (horizontal) datum is a reference ellipsoid plus its position and orientation with respect to a terrestrial reference frame.
	www.imagingnotes.com /novdec99/nd99eoqu.htm (817 words)

	The Global Positioning System reference datum and its relationship with the Indian geodetic datum (Site not responding. Last check: 2007-10-02)
		As the uneven and undulating physical surface of the Earth is not suitable for the mathematical computations of geodetic data reduction and also as a map datum, a hypothetical geometrical reference surface, called 'Geodetic Datum' must be defined.
		Several hundred local geodetic datums are in use in different parts of the world, and many of these have been / are being redefined to meet the ever-increasing accuracy requirements.
		The Indian Geodetic Datum adopted in 1880 is the Everest ellipsoid, which is based upon the adjustment of geodetic data available at that time, computed using the models, techniques and methods in practice then.
	www.gisdevelopment.net /technology/gps/techgp0002pf.htm (386 words)

	[No title]
		A geodetic datum is as defined above, together with the coordinate system and the set of all points and lines whose coordinates, lengths, and directions have been determined by measurement and calculation.
		Before the advent of manmade satellites, geodetic positions in surveying were determined separately, either horizontally in two-dimensions as latitudes and longitudes or vertically in the third dimension as heights or depths.
		Datum transformations are available which relate the NAD 27 and NAD 83 datums, and which relate the NGVD 29 and NAVD 88 datums.
	chartmaker.ncd.noaa.gov /bathytopo/DennisWeb/tutor.doc (3508 words)

	NGA: GEODESY FOR THE LAYMAN
		In geodesy two types of datums must be considered: a horizontal datum which forms the basis for the computations of horizontal control surveys in which the curvature of the earth is considered, and a vertical datum to which elevations are referred.
		A horizontal geodetic datum may consist of the longitude and latitude of an initial point (origin); an azimuth of a line (direction) to some other triangulation station; the parameters (radius and flattening) of the ellipsoid selected for the computations; and the geoid separation at the origin.
		Consequently, the astro-geodetic deflection of the vertical depends upon a specific geodetic datum and the use of geodetic data developed by this method is limited to relatively small areas.
	earth-info.nga.mil /GandG/publications/geolay/TR80003B.html (2890 words)

	Coordinate Systems - A Deeper Understanding (Site not responding. Last check: 2007-10-02)
		Each geodetic datum is defined by a set of numerical elements which define where the imaginary geographical graticule of lines of latitude and longitude lies on the earth's surface, i.e.
		In the case of the newer earth centered and satellite derived geodetic datums, where the datum is effectively the center of the earth ellipsoid, a different type of label with world or international connotations is used, e.g.
		Satellite datums use earth-centered or "Geocentric" ellipsoids whereas the position and orientation of the ellipsoids used for much national mapping was arranged to best fit the data available for the national area at the time, often assuming coincidence of the ellipsoid and geoid surface at the selected datum point.
	www.posc.org /Epicentre.2_2/DataModel/ExamplesofUsage/eu_cs32.html (1745 words)

	GDA94 - GEOCENTRIC DATUM OF AUSTRALIA
		This discussion reviews the spheroids and datums that are used for national and international mapping, the definition of the GDA and its associated geometrical parameters, and presents a rigorous method to update current Australian maps and spatial information systems from the AGD to the GDA.
		This approach enables subsequent geodetic data, which are collected on the physical surface of the earth, to be reduced to the surface of this spheroid without the introduction of significant horizontal scale error.
		To summarise, a regional or geocentric datum comprises geographical coordinates that are referenced to the surface of a particular reference spheroid.
	www.cage.curtin.edu.au /~will/datum.html (5432 words)

	geodetic_datum (Site not responding. Last check: 2007-10-02)
		Modern geodetic datums are defined with respect to the center of the Earth, while historical geodetic datums are defined with respect to fundamental points on the surface of the Earth.
		This should be the code of the geodetic datum, when available, or may be the full name of the geodetic datum when a code is not defined.
		N] of (geodetic_datum_alias) Indicates the various identifiers by which this geodetic datum is known.
	www.august.com /epicentre/local/geodetic_datum.html (247 words)

	Software development & validation for Geodetic Datum Transformations
		A common problem faced by most countries is the estimation of precise transformation parameters between their national geodetic datum, and the World Geodetic System 1984 (WGS84) global datum, used by the Global Positioning System (GPS).
		The process of mathematically converting positions from one datum to the other is known as datum transformation.
		The GPS derived coordinates (which are with respect to the global datum), and the local terrestrial coordinates (which are relative to the local datum of the region) of the lumped points may be processed together using an appropriate transformation model.
	www.gisdevelopment.net /technology/gps/mi03041.htm (352 words)

	NGS FAQs
		"Geodetic positions on the North American Datum of 1927 were derived from the (coordinates of and an azimuth at Meades Ranch) through a readjustment of the triangulation of the entire network in which Laplace azimuths were introduced, and the Bowie method was used." (Geodetic Glossary, pp.
		The datum is defined by the observed heights of mean sea level at the 26 tide gauges and by the set of elevations of all bench marks resulting from the adjustment.
		The North American Vertical Datum of 1988 (NAVD 88) is the vertical control datum established in 1991 by the minimum-constraint adjustment of the Canadian-Mexican-U.S. leveling observations.
	www.ngs.noaa.gov /faq.shtml (5510 words)

	Coordinate Systems (Spatial Reference Systems) (Site not responding. Last check: 2007-10-02)
		geodetic datum is a means of representing the figure of the Earth, usually as an oblate ellipsoid of revolution, that approximates the surface of the Earth locally or globally, and is the reference for the system of geodetic coordinates.
		If the coordinate system is georeferenced, transformation can involve datum transformation: the conversion of geodetic coordinates from one geodetic datum to another geodetic datum, usually involving changes in the shape, orientation, and center position of the reference ellipsoid.
		If you supply a user-defined datum, the datum name must be different from any datum name in the MDSYS.SDO_DATUMS table, and the WKT must specify the datum parameters in the order listed in Section 5.4.1.1.
	www.ucs.louisiana.edu /~oracle9i/appdev.901/a88805/sdo_cs_c.htm (3739 words)

	Geoscience Australia: Geodesy - Australian Geodetic Datum [AGD] (Site not responding. Last check: 2007-10-02)
		The Australian Geodetic Datum (AGD), both the 1966 and 1984 versions, have been replaced by Geocentric Datum of Australia (GDA94).
		The Australian Geodetic Datum was proclaimed in the Australian Commonwealth Gazette of 6 October 1966.
		In 1982 a new national adjustment, referred to as the Geodetic Model of Australia 1982 (GMA82), was performed using all data previously included in the 1966 adjustment as well as additional, modern terrestrial and space-based observations.
	www.ga.gov.au /nmd/geodesy/datums/agd.jsp (408 words)

	RCMRD \| mapping for sustainable development
		Geodetic datum are the basis on which maps, necessary for project planning and implementation.
		The various datums mean different maps for each country and this is not very useful especially for the implementation of regional and cross boundary development projects.
		To rectify this anomaly, the African governments under ECA and OAU resolved that a uniform datum be established for Africa.
	www.rcmrd.org /project1.php (613 words)

	Encyclopedia: Geodetic datum
		A Geodetic Datum is an adjustment to position of origin and shape of the planet, used by cartographers and satellite navigation systems to translate positions indicated on their products to their real position on earth.
		World Geodetic System 1984 (WGS84) - the datum of GPS
		Ordnance Survey of Great Britain 1936 (OSGB36) - the usual datum of British nautical charts and Ordnance Survey maps until 2001
	www.nationmaster.com /encyclopedia/Geodetic-datum (161 words)

	World Geodetic System 1984 - Background (Site not responding. Last check: 2007-10-02)
		A geodetic datum transformation is a mathematical rule used to transform surveyed coordinates given in Reference Frame 1 into coordinates given in Reference Frame 2.
		Hence the accuracy of any datum transformation result is not only dependent on the accuracy of the original data but also on the accuracy of the determination of the transformation parameters used.
		It was agreed that the high accuracy geodetic reference ETRF be used as the realisation of WGS 84 for civil aviation in Europe (refer 4.1.3 in the EUROCONTROL Standard 'Surveying of Navigation Facilities').
	www.wgs84.com /wgs84/wgs84.htm (1736 words)

	FAQs Geodetic, Datum and Projection
		It is a static datum because the coordinates of the trig stations defining the datum (1st order stations) have been held fixed since they were defined in 1949.
		It is a semi-dynamic datum incorporating a velocity model with coordinates aligned to the International Terrestrial Reference Frame 1996 (ITRF96) at a reference date of 1 January 2000 (epoch 2000.0).
		NTv2 is a format developed by the Geodetic Survey of Canada specifically for the purpose of distributed grid transformation data.
	www.linz.govt.nz /rcs/linz/pub/web/root/core/SurveySystem/SurveyPublications/nzgdfaq/index.jsp (2264 words)

	Relation of NAD 83 To WGS 84
		With local horizontal datums, these quantities were fixed by specifying the geodetic coordinates of an initial point and at least one azimuth.
		This specification is usually supplemented by a second definition which states that a horizontal geodetic datum is composed of the adopted horizontal coordinates of a set of physical points in that datum.
		geographically overlapping datums (in the sense of datum as adopted coordinates).
	www.mentorsoftwareinc.com /resource/Nad83.htm (2304 words)

	DIGEST Part 3 Clause 6 GEODETIC CODES AND PARAMETERS (Site not responding. Last check: 2007-10-02)
		In some cases a geodetic datum with a 3-letter code is followed by 4-letter codes referring to the same datum but specifying particular regions.
		In the case of an unknown or unspecified datum, it is potentially dangerous to assume a default of WGS 84.
		In the geodetic case, all elevations in the dataset are referenced to the ellipsoid of the specified geodetic datum, which means they are ellipsoidal heights.
	www.digest.org /html/gp36.htm (1511 words)

	GPS Waypoints World Geodetic System 1984
		This Datum is based on the Clarke 1880 ellipsoid and has its origin point at Buffelsfontein near Port Elizabeth.
		In addition to these flaws and distortions, most national geodetic networks do not have the centre of their reference ellipsoids co-incident with the centre of the Earth thus making them useful only to their area of application.
		The introduction of the Hartebeesthoek94 Datum will ensure that South Africa remains at the forefront of modern geodetic networks and provides us with a Datum that is internationally related and relevant to our user needs.
	www.gpswaypoints.co.za /FAQ_world_geodetic_system_1984.htm (1511 words)

	NZ Geodetic Datum 2000 Factsheet
		A datum is a mathematically defined reference surface, approximating the shape of the earth, that enables calculations such as position and area to be carried out in a consistent and accurate manner.
		The datum is physically represented by a framework of ground monuments (i.e.
		New Zealand Geodetic Datum 1949 (NZGD49) was introduced to meet the needs for an integrated spatial reference system and complete topographical and cadastral mapping database coverage of New Zealand.
	www.linz.govt.nz /rcs/linz/pub/web/root/core/SurveySystem/GeodeticInfo/GeodeticDatums/nzgd2000factsheet/index.jsp (1037 words)

Try your search on: Qwika (all wikis)