General Vertical Near-side Perspective

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General Vertical Near-side Perspective presents a picture of the Earth as if a photograph were taken at some distance less than infinity. The map user simply identifies area of coverage, distance of view, and angle of view. It is a variation of the General Perspective projection in which the "camera" precisely faces the center of the Earth.

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Plane

Property

Compromise

Meridians

The central meridian is a straight line in all aspects. In the polar aspect all meridians are straight. In the equatorial aspect the Equator is straight (Environmental Systems Research Institute, 1992).

Parallels

Parallels on vertical polar aspects are concentric circles. Nearly all other parallels are elliptical arcs, except that certain angles of tilt may cause some parallels to be shown as parabolas or hyperbolas.

Graticule spacing

Polar aspect: parallels are concentric circles that are not evenly spaced. Meridians are evenly spaced and spacing increases from the center of the projection.

Equatorial and oblique aspects: parallels are elliptical arcs that are not evenly spaced. Meridians are elliptical arcs that are not evenly spaced, except for the central meridian, which is a straight line.

Linear scale

Radial scale decreases from true scale at the center to zero on the projection edge. The scale perpendicular to the radii decreases, but not as rapidly (Environmental Systems Research Institute, 1992).

Uses

Show the Earth or other planets and satellites as seen from space. Used as an aesthetic presentation, rather than for technical applications (Environmental Systems Research Institute, 1992).

Central meridian and a particular parallel (if shown) are straight lines. Other meridians and parallels are usually arcs of circles or ellipses, but some may be parabolas or hyperbolas. Like all perspective projections, General Vertical Near-side Perspective cannot illustrate the entire globe on one mapit can represent only part of one hemisphere.

This projection contains these unique parameters:

Height of perspective point    Value for the desired height of the perspective point above the sphere in the same units as the radius.

Then, define the center of the map projection in both spherical and rectangular coordinates.

Longitude of center of projection

Latitude of center of projection