What Is Datum?
Definitions of datum on the Web:
- For
marine applications, a base elevation used as a reference from which to
reckon heights or depths. It is called a tidal datum when defined in
terms of a certain phase of the tide. Tidal datums are local datums,
referenced to fixed points (bench marks), and should not be extended
into areas that have differing hydrographic characteristics without
substantiating measurements.
amsglossary.allenpress.com/glossary/browse - a fixed reference point on an archaeological site from which measurements are taken.
www.china.org.cn/english/features/Archaeology/98851.htm - A
set of parameters and control points used to accurately define the
three-dimensional shape of the Earth (eg, as a spheroid). The datum is
the basis for a planar coordinate system. For example, the North
American Datum for 1983 (NAD83) is the datum for map projections and
coordinates within the United States and throughout North America.
www.mcaggis.com/glossary.htm - symbol that describes an aspect of an entitiy or event in the real world. Statistical datatypes: dead key
techref.massmind.org/techref/glossary.htm - A
set of constants specifying the coordinate system used for geodetic
control. A complete geodetic datum provides, as a minimum, definition
for orientation, scale and dimensions for the reference ellipsoid. The
concept is generally expanded to include the published coordinates of
control stations within the system.
www.rbf.com/cgcc/glossary.htm - A
datum is a model of the surface of the earth based on a surveyed
network of physical points. In the US, the most common is the North
American Datum of 1927 (NAD27). This datum is used on USGS and USDAFS
(USDA Forest Service) maps along with many other government and private
maps. There are over a 100 other datums in use throughout the world.
www.seilerinst.com/gps/gpsterms.asp - is an elevation above mean sea level to which all gage height readings are referenced.
nd.water.usgs.gov/canoeing/glossary.html - "1.
Any point, line, or surface used as a reference for a measurement of
another quantity. 2. A model of the earth used for geodetic
calculations" (Bonham-Carter, 1994, p. 356).
www.gis.state.ar.us/Documents/gisprimer/definitions.html - Any level surface taken as a plane of reference from which to measure elevations.
www.hydro.mb.ca/our_facilities/build_gen_station/glossary.html - a
single fact, as in: We based our measurements on the datum of the
boiling point of water. (Note: rarely used outside scientific
literature)
www.business-words.com/dictionary/D.html - All
ground surface elevations are measured from a certain point called a
datum. Once TSARP is completed all of the elevation data for Harris
County will be on NAVD 1988 2001 Adjustment Datum.
www.tsarp.org/glossary.html - 1.
Any numerical or geometrical quantity or set of such quantities which
may serve as a reference or base for other quantities. 2. See chart
datum
www.usm.edu/gcrl/MStide/tideglos.htm - An application-specific data structure associated with a Clause that is the thing that the Clause describes.
ic.arc.nasa.gov/projects/L2/doc/L2_refman/L2Glossary.html - a fixed or established point of reference, usually with a fixed elevation
www.landscapemodeling.org/html/glossary/glossary.htm - (pl. datums) A point, line, or surface used as a reference, as in surveying or mapping.
www.maps-gps-info.com/maps-gps-glossary.html - Something used as the basis for reasoning, inference, calculating, or measuring. A reference point or origin for mapping.
www.nps.gov/maca/learnhome/cur_p_glo.htm - A
point, line, surface or set of quantities used as a reference upon
which measurements are based. (source -Survey Services 2003)
web2.gov.mb.ca/mli/glossary/a_d.html - A
reference system for vertical and horizontal positions. Different
datums have different positions for the physical location of their
origins, thus different datums will represent coordinates in different
positions. Differences can be as much as a mile. All reliable maps that
show coordinate systems provide Datum information.
gpsscales.com/glossary.htm - Imaginary line from which all measurement of arms are taken.
home.swipnet.se/~w-65189/glossary.htm - A
reference surface consisting of the following parameters: the latitude
and longitude of an initial point (origin), the orientation of the
network, and the two parameters of a reference ellipsoid. Coordinates
for a particular ground location will vary based on the datum used to
produce a particular map or chart. Therefore, it is essential that the
datum used to derive the coordinates be included when reporting
positions. ...
earth-info.nga.mil/GandG/coordsys/definitions.htm - In
mapping, a numeric or geometric quantity which serves as a reference or
base to accurately define other quantities. It most often refers to
either a horizontal standard, such as a particular spheroid for
referencing coordinate positions, or it refers to a vertical datum,
such as mean sea level, from which elevations are referenced.
geoapp2.gov.mb.ca/website/MAFRI/Glossary3.html - a location from which all measurements on a site are made; a reference point tied to local survey maps.
darkwing.uoregon.edu/~mmoss/GLOSSARY.HTM - A
datum describes the survey model that was used to match the location of
features on the ground to coordinates and locations on a map. In Canada
and the United States early topographic maps were based on the North
American Datum 1927 (NAD27). More recent topographic maps are based on
a North American Datum 1983 (NAD83). The Global Positioning System uses
an earth-centered datum called the World Geodetic System 1984 (WGS84).
...
www.foothills-sar.ab.ca/glossary.html - A
reference ellipsoid is used with an "initial point" of reference on the
surface to produce a datum, the name given to a smooth mathematical
surface that closely fits the mean sea-level surface throughout the
area of interest. The "initial point" is assigned a latitude, longitude
and elevation above the ellipsoid. Once a datum is adopted, it provides
the surface to which ground control measurements are referred.
www.montana.edu/places/gps/lres357/glossary.html - Geographical reference frame, horizontal plane based on a vertical benchmark (such as mean sea level)
cwest.oregonstate.edu/streamflow/mainpage/Terminology1.htm - an item of factual information derived from measurement or research
wordnet.princeton.edu/perl/webwn - 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 used to
measure elevations or underwater depths.
