# cylindrical projections

## cylindrical projections

A cylindrical map projection onto a cylinder tangent to a sphere, showing the geographic meridians as a family of equal-spaced parallel straight lines perpendicular to a second family of parallel straight lines. They represent the geographic parallels and are so spaced as to produce an equal-area map projection. The equal-area condition preserves a constant ratio between corresponding ground and map areas. This projection must not be confused with the Mercator projection, to which it bears some general resemblance. True or correct scale will obtain along the great circle of tangency or the two homothetic small circles of intersection. If the axis of the cylinder is parallel to the axis of the earth, the parallels and meridians will appear as right, perpendicular lines. Points on the earth equally distant from the tangent great circle (equator) or small circles of intersection (parallels equally spaced on either side of the equator) will have equal scale departure. The pattern of deformation will therefore be parallel to the parallels, as a change in scale occurs in a direction perpendicular to the parallels. If the cylinder is turned 90° with respect to the earth's axis, the projection is said to be transverse, and the pattern of deformation will be symmetric with respect to a great circle through the poles. If the turn of the cylinder is less than 90°, an oblique projection results.
References in periodicals archive ?
The application creates pseudocylindrical and cylindrical projections, as well as projections with curved parallels.
The two "starter" projections are often a cylindrical projection, such as the plate carree and a pseudocylindrical projection with meridians converging at pole points.
Gahrken demonstrated that these features recorded by himself and others do sometimes but not always correspond to surface features, by comparison of cylindrical projections of these images with both Magellan radar mapping and images from Venus Express.
Can those orderly little cylindrical projections below a primitive capital be vague memories of Doric guttae?
Distinguished from cylindrical projections by curved meridians, but sharing the pattern of latitude, the pseudocylindrical projection emerged as a favorite design concept for new projections as the 20th century began (Snyder 1993; Delmelle 2991).
Geometrically, cylindrical projections can be developed by unrolling a cylinder which has been wrapped around the Earth and touches at the equator.
In the case of equivalency, the infinitely small area dF in Equation (2a) on the sphere equals to an infinitely small area df on the projection plane and for the cylindrical projections, this may be expressed as:
For example, cylindrical projections where x = [lambda] and y = f([phi]), such as the cylindrical equal area, Mercator and Miller, should have a basic pattern of horizontal lines on the DLDM, with the spacing of lines defined by the inverse map projection equation for latitude.

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