Datum A set of parameters and control points used to accurately define the threedimensional shape of the Earth (e.g., as a spheroid). The corresponding datum is the basis for a planar coordinate system.
 Defines the origin, orientation and scale of the coordinate system and ties it to the earth, ensuring that the abstract mathematical concept 'coordinate system' ...
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GIS Dictionary > GIS Dictionary Definitions for GIS terms related to operations such as analysis, GIS modeling and webbased GIS, cartography, and Esri software.
Map Datums A datum describes the model that was used to match the location of features on the ground to coordinates and locations on the map. Maps all start with some form of survey.
: A math model which depicts a part of the surface of the earth. Latitude and longitude lines on a paper map are referenced to a specific map .
Reference Datum A reference datum is a known and constant surface which can be used to describe the location of unknown points. On Earth, the normal reference datum is sea level.
You are publishing a tiled map service using the ArcGIS Online/Google Maps/Bing Maps tiling scheme and there is no transformation from your data frame's to WGS 1984 Major Auxiliary Sphere.
Datum: A reference location or elevation which is used as a starting point for subsequent measurements. Sea level is a datum for elevation measurements.
S 41. The earth is an ellipsoid, not a sphere, flattened slightly at the poles and bulging somewhat at the equator.
Datum, Spheroids and Ellipsoids Unlike local surveys, which treat the Earth as a plane, the precise determination of the latitude and longitude of points over a broad area must take into account the actual shape of the Earth.
s 1  the Basics A is a system which allows the location of latitudes, longitudes and heights to be identified onto the surface of the Earth. As s is a jargon rich subject it is recommended that you read this section first.
Datum A datum is a mathematical surface on which a mapping and coordinate system is based.
: In mapping, a numeric or geometric quantity which serves as a reference or base to accurately define other quantities.
Datum  A reference surface for a particular coordinate system. Defines the mathematical relationship by which a feature relates to its original surface in a specific coordinate system.
s s are sets of parameters and ground control points defining local coordinate systems.
Datums A datum is a starting point for locating features on the Earth's surface; it is the origin point of a coordinate system. It defines the position of the ellipsoid (or spheroid) relative to the Earth's center.
The For highly precise maps of smaller regions, the basic ellipsoidal shape can not be ignored. A geodetic is a set of parameters (including axis lengths and offset from true center of the Earth) defining a reference ellipsoid.
The Datum Selection Option The selection of the DRG Clipper Button will prompt the user to identify the current datum of the 24K DRG files as shown below.
A point, line, or surface reference from which coordinate systems are derived for surveying and mapping. DNR Louisiana Department of Natural Resources.
Datum transformations using Molodensky equations (implemented in most geosoftware) are becoming increasingly important, because of the growing use of GPS data.
conversions are automatically handled by the PROJ.4 library if "+" setings are specified on both the input and output projections on the command line.
Datum Notes: Spatial data are referenced to a horizontal datum and a vertical datum, both of which are based on a mathematically calculated shape of the earth.
s can be vertical, horizontal, or complete. Vertical s deal primarily with elevation and are usually developed to supplement existing s.
Datum Point, line or surface used as a reference for a measurement of another quantity. Point, line, or surface used as a reference (i.e., surveying, mapping, or geology).
 A point, line or surface selected as the origin or reference for measurements. A can be mathematically defined (e.g. the Earth's ellipsoid) or established by field observations (e.g. the mean sea level).
The datum established in 1929 by the U.S. Coast and Geodetic Survey as the surface against which elevation data in the United States is referenced. Referenced by: North American Vertical Datum of 1988; Elevation; Sea Level Datum of 1929.
Geodetic : A set of parameters defining coordinate systems for all or parts of the earth. These s have been refined and revised over time. NAD 27 is the North American for 1927, for example.
Geodetic Datum These materials were developed by Peter H. Dana, Department of Geography, University of Texas at Austin, 1995. These materials may be used for study, research, and education in notforprofit applications.
Multiple LRS and color coding of complex infrastructure objects often result in misleading or incorrect computation, identified by Sutton (1996) as network pathologies.
Geodetic Datums Distance Between Degrees Topo Maps Related Articles 100th Meridian Stand On The Prime Meridian  London for Free  Greenwich Meridian Line Latitude and Longitude Video ...
Changing s (for example, from NAD 27 to NAD 83) can be difficult or cumbersome. Projections are usually implemented using power series approximations that might be inadequate for high precision work.
Geocentric datum relate coordinates to the earth's center of mass. Such datum have been improved by modern satellite data.
BenchmarkA brass or bronze disk set in a concrete base or other permanent structure, inscribed with a mark showing its elevation above or below an adopted vertical .
cartographic representative of the surface of the Earth or a subsurface feature through a series of threedimensional coordinate values: a continuous variable over a twodimensional surface by a regular array of z values referenced to a common .
An estimate of the earth's surface based on an ellipsoid provides a determination of the elevation of every point on the earth's surface, including sea level, and is often called a .
A digital representation of a continuous variable over a twodimensional surface by a regular array of z values referenced to a common . Digital elevation models are typically used to represent terrain relief.
There is another critical bit of information that is required before you are totally confused: the . The need for a is the consequence of man's inability to describe mathematically the exact shape of the earth.
This function supports most geodetic used around the world. This function can convert the control points or be applied to a single point. For 3D VRML export, the output file now includes color and image draping information.
Geodetic s (Dana/Geographer's Craft)  Introduction to geodetic s; Figure of the earth: geometric models, reference ellipsoids, global coordinate systems, earth surfaces; Geodetic s.
This conversion requires both a transformation between ellipsoids and a shift. Numerous s have been used for mapping around the world. For details, see Snyder (1987; 1989).
The software performs transformation on raster and vector data sometimes of differing s, grid system, or reference system, into one coherent image. It can also analyse changes over time within a region.
All parametric equipment types include at least one nozzle manager . Vertical vessel with legs (TANK_V4LEG) correctly orients legs straddling the axis of the vessel. Label tool selects individual equipment nozzles.
But the earth's mountains bumpup and valleys bumpdown from the ellipsoid so a is designed to fit the earth's surface that accounts for the actual wrinkling of the globe as established by orbiting satellites.
Take a look at the projection definition you copied (Imported) for the la_to_ny shapefile you created with ArcToolbox, what Spheroid was used with the ? 3b. Briefly state what the difference between Spheroid and is. 3c.
Geodetic Overview, Department of Geography, University of Colorado at Boulder Global Positioning System Overview, Department of Geography, University of Colorado at Boulder ...
Geodetic s Overview The Mercator Conformal Projection Norris Wiemer, University of Alberta. John Snyder An obituary of the man who achieved immortality by computerizing the mathematical algorithms for transforming map projections.
Attributes (see description above); Geographic information describing the position of the in space relative to other data; and Temporal information describing the instant or period of time for which the is valid.
This should at least include dataset names with descriptions of what they contain, coordinate system & , theoretical accuracy, source document names with dates & scales, data conversion methods, update history, ...
The data related to a particular part of the Earth surface are often in different format, have different georeferencing ( heterogeneity, projection heterogeneity, etc.), end different resolution.
Data editing Data manipulation Edgematching conversions, transformations, and projections Topology building Data structuring Attaching data attributes to graphics Data format conversions ...
altitude  elevation above or below a reference , as defined in Federal Information Processing Standard 701. See also elevation.
A reference system that uses latitude and longitude to define the locations of points on the surface of a sphere or spheroid. A geographic coordinate system definition includes a , prime meridian, and angular unit. Layer1 ...
These include data layer classifications, source media and digitizing standards, s, projections, coordinate systems, cartographic elements, and output scales.
NAD  North American : The official reference ellipsoid used for the primary geodetic network in North America. Node: The beginning and ending locations of a line on a digital map.
ArcInfo supports these transformations: similarity, affine, piecewise linear, projective, NADCON adjustment using minimumderived curvature transformation, and a polynomial transformation to warp grids and images.
See also: Map, Geographic, Coordinate, Information, Surface
