## Classification

Cylindrical

## Graticule

Meridians: Equally spaced straight parallel lines.

Parallels: Unequally spaced straight parallel lines, perpendicular
to the meridians. Spacing increases toward the poles.

Poles: Cannot be shown.

Symmetry: About any meridian or the Equator.

## Features

This is a projection with parallel spacing calculated to maintain
conformality. It is not equal-area, equidistant, or perspective. Scale
is true along the standard parallels and constant between two parallels
equidistant from the Equator. It is also constant in all directions
near any given point. Scale becomes infinite at the poles. The appearance
of the Mercator projection is unaffected by the selection of standard
parallels; they serve only to define the latitude of true scale.

The Mercator, which may be the most famous of all projections,
has the special feature that all rhumb lines, or loxodromes (lines
that make equal angles with all meridians, i.e., lines of constant
heading), are straight lines. This makes it an excellent projection
for navigational purposes. However, the extreme area distortion makes
it unsuitable for general maps of large areas.

## 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, any latitude less than 86º may be
chosen; the default is arbitrarily set to 0º.

## Remarks

The Mercator projection is named for Gerardus Mercator, who
presented it *for navigation* in 1569. It is now
known to have been used for the Tunhuang star chart as early as 940
by Ch'ien Lo-Chih. It was first used in Europe by Erhard Etzlaub in
1511. It is also, but rarely, called the Wright projection, after
Edward Wright, who developed the mathematics behind the projection
in 1599.

## Limitations

Data at latitudes greater than 86º is trimmed to prevent
large *y*-values from dominating the display.

## Example

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