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# Central Meridian

Central Meridian
central meridian - [coordinate systems] The line of longitude that defines the center and often the x-origin of a projected coordinate system.

central meridian
the longitude of the horizontal center of a coordinate system (this longitude value is often the longitude origin of the coordinate system); in the case of the transverse Mercator projection, ...

Central Meridian
The meridian that passes through the poles and origin of an ellipsoid/sphere representing the earth and is used in calculations of a specific projection.
Central Processing Unit (CPU) ...

central meridian
A central meridian is a meridian that passes through the center of a projection. The central meridian is often a straight line that is an axis of symmetry of the projection.
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Central meridian and lines perpendicular to it
Central Clindrical
Classification: ...

~ - A line running North and South, at the center of a graticule, along which all points have the same longitude. See also Meridian.
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~
The line of longitude that defines the center and often the x-origin of a projected coordinate system. In planar rectangular coordinate systems of limited extent, such as state plane, grid north coincides with true north at the ~.

the ~ is straight, half as long as the Equator, and a standard line in odd-numbered projections
poles are flat, half as long as the Equator
even-numbered projections are equal-area
odd-numbered projections have equally spaced parallels ...

the ~ is the meridian where the cylinder touches the sphere
theoretically, the ~ is the line of zero distortion
by rotating the cylinder around the poles
the ~ (and area of least distortion) can be moved around the earth ...

Distances are only correct along parallels and ~. Shapes become more distorted away from the ~ and close to the poles. Slaking See wetting and drying.

Select the Projection Lambert_Azimuthal_Equal_Area. Alter the ~ and Latitude of Origin.
It is also necessary to select a datum (Geographic Coordinate System). Click Select and find North America > North American Datum 1927.prj.

Map makers have technical terms to describe the line of latitude or longitude where this imaginary 'piece of paper' touches the Earth. These are:
for a line of latitude - standard parallel
for a line of longitude - ~
Azimuthal Projections ...

Other projection mathods are based on more complicated flattenable projection surfaces, and instead of points of tangency, spacial cases of these projections can be made by adjusting their Standard Paraslells or ~s ...

Just as the normal aspect Mercator projection has low distortion of scale near the equator, so does a transverse Mercator projection have low scale distortion near its ~. With the UTM system, the earth is divided into 60 zones of longitude, each 6 degrees of longitude wide.

The origin of each UTM zone is the intersection of its ~ and the equator, and the parameters are applied to this origin to make it convenient to work with making all x and y values positive, or reducing their range.

The UTM easting coordinate (the X coordinate) for a feature is the distance in meters east or west from the ~ of the UTM zone. The ~ for UTM zone 10 (with boundaries at 120° west longitude and 126° west longitude) is 123° west longitude.

and is the longitude from the ~, and is the latitude.
The Mollweide is a pseudocylindrical projection in which the equator is represented as a straight horizontal line perpendicular to a ~ one-half its length.

There is a false origin defined at 400,000, -100,000 such that the ~ is the Zero easting of the National Grid - which is also aligned to the 2 degree West meridian of Longitude. Additionally, the scale along the ~ is 0.

To eliminate the necessity for using negative numbers to describe a location, the east-west origin is placed 500,000 meters west of the ~. This is referred to as the zone's ‘false origin'. The zone doesn't extend all the way to the false origin.

Within each zone the ~ is given an Easting value of 500,000 metres. The equator is designated as having a Northing value of 0 for northern hemisphere coordinates. Coordinates are recorded relative to the ~ in metres in a particular zone.

Put another way: UTM projection is used to define horizontal positions world-wide by dividing the surface of the Earth into 6 degree zones, each mapped by the Transverse Mercator projection with a ~ in the center of the zone.

Enter Central Parallel: 0 if you want the Equator as the central parallel
Enter ~: 0 if you want the Greenwich meridian as ~
Enter Scale Factor at the ~
Enter plural form of map units: for example, meters ...

Transverse Mercator projections result from projecting the sphere onto a cylinder tangent to a ~. Transverse Mercator maps are often used to portray areas with larger north-south than east-west extent.

UTM zones have an origin on the equator at the point where the ~ of the zone intersects. Coordinates are measured in meters from the false origin followed by the zone number and the hemisphere.

Each zone has an arbitrary ~ of 500 km west of each zone's ~ (called a false Easting) to insure positive Easting values and a central bisecting meridian.

The projection is true to scale along the ~ and along each parallel. It is neither conformal nor equal-area, and it is only free of distortion along the ~. Therefore, it should only be used for regions of predominant north-south extent.

UTM easting coordinates are referenced to the center line of the zone known as the ~. The ~ is assigned an easting value of 500,000 meters East. Since this 500,000m value is arbitrarily assigned, eastings are sometimes referred to as "false eastings" ...

The easting coordinates are measured from an artificial reference line drawn parallel and 500,000 meters to the west of the zone's ~. (Thus each ~ is numbered 500,000.) The third figure shows the ten UTM zones spanning the United States.

Using Spatial Analyst this tile was clipped, warped with an order-three polynomial to approximate an Equidistant Conic projection (Clarke 1866 spheroid, ~ 71 degrees west, reference latitude 19 degrees north, standard parallels at 21 and 17 degrees north), ...

A coordinate system is usually defined by a map projection, a spheroid of reference, a datum, one or more standard parallels, a ~, and possible shifts in the x- and y-directions to locate x,y positions of point, line, and area features.

[ESRI software] In Survey Analyst for field measurements, any meridian that is parallel to the ~, used when computing points in planar rectangular coordinate systems of limited extent.

The UTM divides the world into 60 zones of 6 degrees longitude. Each zone extends 3 degrees east and west from its ~ and are numbered consecutively west to east from the 180-degree meridian. Transverse Mercator projections may then be applied to each zone.

There are two geoprocessing tools available from the Data Driven Pages toolset in the Cartography toolbox to help you populate a spatial reference field: Calculate ~ and Parallels and Calculate UTM Zone.

into an AutoCAD Map 3D drawings Cartesian coordinate system, and accounts for the curvature of the surface of the Earth with a projection. A coordinate system is usually defined by a projection, an ellipsoid definition, a datum definition, one or more standard parallels, and a ~.

Eastings are in meters with respect to a ~ drawn through the center of each grid zone (and given an arbitrary easting of 500,000 meters). In the northern hemisphere, northings are read in meters from the equator (0 meters).

A transverse cylindric projection uses a meridian of longitude as its ~. travelling salesman problem p. 203 given a graph connecting a set of nodes, devise a route that visits each node in the graph exactly once and minimizes the total cost accumulated. trend surface p.

See also: What is the meaning of Meridian, Projection, Map, Parallel, Area?