The quantities or relations which are assumed to be given in any problem.
a point, line, or level surface used as a reference in measuring elevations.
The horizontal plane to which soundings, ground elevations, or water surface elevations are referenced. Some examples of a datum are: Mean high water Mean higher high water Mean low water Mean lower low water Mean sea level Mean tide level National Geodetic Vertical Datum
(n) A theoretically exact point, axis, or plane used as a reference for tabular dimensioning. A datum marks the origin from which the location and orientation of geometric features are established.
A set of parameters specifying the reference surface or the reference coordinate system used for geodetic control in the calculation of coordinates of the points of the earth. Commonly, datums are defined as horizontal and vertical datums separately. For the practical use of datum it is necessary to have one or more well monumented points with coordinates given in that datum.
A reference point from which movements or measurements are made. A datum can lie anywhere on the surface of a work piece. A datum can be a coordinate but does not have to have a physical feature.
Properly, is the singular for the word data. In mapping, it is the assumed horizontal surface of zero elevation. This surface forms a spheroid (defined mathematically) and is meant to approximate the shape of the earth. Survey control positions are relative to a given datum. See NAD27, NAD83.
a fixed or established point of reference, usually with a fixed elevation
a fixed reference point on an archaeological site from which measurements are taken.
Standard or common reference base or system.
Something used as the basis for reasoning, inference, calculating, or measuring. A reference point or origin for mapping.
(pl. datums) A point, line, or surface used as a reference, as in surveying or mapping.
The units of latitude and longitude, each datum describes the shape of the Earth differently. Most GPS units use the datum WGS-84, while older maps in the US use NAD27.
(1) In general terms, a single isolated piece of information. (2) A fixed reference point or basis to which other information is related. (3) A set of accurately surveyed horizontal control points that define the shape of the Earth as a spheroid and form the basis for a 2-dimensional coordinate system. (4) A vertical datum is a level surface of reference (usually mean sea level or the geoid) from which elevations are measured. (See -North American Datum 1983 (NAD 83) and Spheroid).
The point from which measurements are taken.
(pl. datums) A model of the earth's surface that is comprised of a network of physical points that serves as a reference for maps, for both horizontal and vertical data. In the U.S. early topographic maps were based on the North American Datum 1927 (NAD27). More recent maps are based on a North American Datum 1983 (NAD83). GPS uses a datum called World Geodetic System 1984 (WGS84). There are over 100 datums in use around the world.
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. Back
Based upon a spheroid, a datum acts a starting point for making the most accurate measurements on Earth's surface. A datum is a local point of reference, and as such there is a different datum for almost every region of the planet.
A reference point of starting elevations used in mapping and surveying.
A base or reference elevation used as the origin to define subsequent elevation. Often refers to mean sea level.
A reference location or elevation which is used as a starting point for subsequent measurements. Sea level is a datum for elevation measurements. Datums can also be arbitrary such as the starting point for stream stage measurements or based upon a physical feature such as the base of a rock unit.
A value that serves as a reference for measuring other values of the same quantity.
is an elevation above mean sea level to which all gage height readings are referenced.
A datum is a network of monuments and reference points defining a mathematical surface from which geographic computations can be made. [Section 4.3.1.1
a "base value" or "reference value" from which other values can be calculated
a feature or group of features of a part selected for use as a base from which other features or points are located within specified limits
a fixed point that anchors a sketch point to a specified location
a fixed, three-dimensional surface, an oblate spheroid, that is approximately the size and shape of the Earth
a form which ascribes data mathematically along a grid standard for map production
a frame of reference when plotting locations on a globe
a framework that enables us to define coordinate systems
a geodetic reference system that specifies the size and shape of the earth, and the base point from which the latitude and longitude of all other points on the earth's surface are referenced
a known or assumed point used as a basis for inference or reckoning
a location-specific reference surface to which all measurements are reduced for locational referencing
a mathematical figure that best fits the shape of the Earth
a mathematically defined reference surface which approximates the shape of the earth, and enables calculations such as position and area to be carried out in a consistent and accurate manner
a mathematical model of the earth used to calculate the coordinates on a map, chart, or survey system
a mathematical model of the Earth which approximates the shape of the Earth, and enables calculations such as position and area to be carried out in a consistent and accurate manner
a mathematical model of the world's shape, and is used to calculate the coordinates on any map or chart
a mathematical model that describes the size and shape of the Earth (an ellipsoid) and provides the origin and orientation of the coordinate system
a mathematical model that represents the shape of the earth
a mathematical representation of the earth
a mathematical surface on which a mapping and co-ordinate system is based
a means by which coordinates determined by any means may be related to a well-defined Reference Frame
a model of the surface of the earth based on a surveyed network of physical points
an attempt by map makers to correct for the fact that the earth isn't perfectly round, but rather elliptical in shape
a plane that extends off to infinity
a point, a line, or surface used as a reference in surveying and mapping
a point of known location or elevation, from which other locations or elevations can be measured
a point on the earth's surface that is used to anchor a map
a reference for physical parameters such as the shape of the earth
a reference point of known or assumed height to which all other site levels will refer
a regional or global coordinate reference system
a set of constants or control points that specify the coordinate system used for geodetic control, i
a set of control points whose geometric relationships are known, either through measurement or calculation, and is used to define a coordinate system
a set of parameters defining a coordinate system, and a set of control points whose geometric relationships are known, either through measurement or calculation
a set of parameters which define the coordinate system of a projection
a smoothed mathematical surface of the earth's mean, sea- level surface
a specialized coordinate reference concept that also includes an Ellipsoid - a definition of the exact non-sphericity of the planet
a standard representation of shape and offset for coordinates, which includes an ellipsoid and an origin
a surveyed line or point that ensures all maps within a series will correctly match when placed edge to edge
a surveying or referencing system used as a basis for calculating and/or measuring geographic locations
Any point, line or surface used as a reference for a measurement of another quantity. A model of the earth used for Geodetic calculations. A more complete explanation is available in the Standards Section.
A network of precisely-surveyed control points used as a reference for measurements of other horizontal or vertical positions. For global-scale measurements, the WGS 84 ellipsoid also serves as a datum. Reference: Peter Dana, The Geographer's Craft
a mathematical reference framework for geodetic coordinates defined by the latitude and longitude of an initial point, the azimuth of a line from this point, and the parameters of the ellipsoid upon which the initial point is located. In regard to usage in this catalog, datum is identifying which system the coordinates are based upon (NAD27 or NAD83)
A position or element in relation to which others are determined. Datum Line: A line from which distances or dimensions are reckoned. Datum Plane: A plane from which distances or dimensions are reckoned. Datum point: A point used as the basis for reckoning.
A datum is something used as a basis for calculating and measuring. In the case of GPS, datums are different calculations for determining longitude and latitude for a given location. Currently, Geocaching uses the WGS84 datum for all caches. Many maps still use NAD27, which can cause confusion if your GPS unit is set to NAD27. Always check your GPS to ensure that WGS84 is the datum before entering a cache coordinate into your unit.
