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Wetch Cylindrical Projection

Classification

Cylindrical

Identifier

wetch

Graticule

Central Meridian: Straight line (includes meridian opposite the central meridian in one continuous line).

Other Meridians: Straight lines if 90º from central meridian, complex curves concave toward the central meridian otherwise.

Parallels: Complex curves concave toward the nearest pole.

Poles: Points along the central meridian.

Symmetry: About any straight meridian or the Equator.

Features

This is a perspective projection from the center of the Earth onto a cylinder tangent to the central meridian. It is not equal-area, equidistant, or conformal. Scale is true along the central meridian and constant between two points equidistant in x and y from the central meridian. There is no distortion along the central meridian, but it increases rapidly away from the central meridian in the y-direction.

Parallels

For cylindrical projections, only one standard parallel is specified. The other standard parallel is the same latitude with the opposite sign. For this projection, which is the transverse aspect of the Central Cylindrical, the standard parallel of the base projection is by definition fixed at 0º.

Remarks

This is the transverse aspect of the Central Cylindrical projection discussed by J. Wetch in the early 19th century.

Limitations

This projection is available only for the sphere. To prevent large y-values from dominating the display, data at y-values that would correspond to latitudes of greater than 75º in the normal aspect of the Central Cylindrical projection is trimmed.

Example

landareas = shaperead('landareas.shp','UseGeoCoords',true);
axesm ('wetch', 'Frame', 'on', 'Grid', 'on');
geoshow(landareas,'FaceColor',[1 1 .5],'EdgeColor',[.6 .6 .6]);
tissot;

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