# Albers Equal-Area Conic Projection

## Graticule

Meridians: Equally spaced straight lines converging to a common
point, usually beyond the pole. The angles between the meridians are
less than the true angles.

Parallels: Unequally spaced concentric circular arcs centered
on the point of convergence. Spacing of parallels decreases away from
the central latitudes.

Poles: Normally circular arcs, enclosing the same angle as the
displayed parallels.

Symmetry: About any meridian.

## Features

This is an equal-area projection. Scale is true along the one
or two selected standard parallels. Scale is constant along any parallel;
the scale factor of a meridian at any given point is the reciprocal
of that along the parallel to preserve equal-area. This projection
is free of distortion along the standard parallels. Distortion is
constant along any other parallel. This projection is neither conformal
nor equidistant.

## Parallels

The cone of projection has interesting limiting forms. If a
pole is selected as a single standard parallel, the cone is a plane
and a Lambert Azimuthal Equal-Area projection results. If two parallels
are chosen, not symmetric about the Equator, then a Lambert Equal-Area
Conic projection results. If a pole is selected as one of the standard
parallels, then the projected pole is a point, otherwise the projected
pole is an arc. If the Equator is chosen as a single parallel, the
cone becomes a cylinder and a Lambert Equal-Area Cylindrical projection
is the result. Finally, if two parallels equidistant from the Equator
are chosen as the standard parallels, a Behrmann or other equal-area
cylindrical projection is the result. Suggested parallels for maps
of the conterminous U.S. are [29.5 45.5]. The default parallels are
[15 75].

## Remarks

This projection was presented by Heinrich Christian Albers in
1805.

## Limitations

Longitude data greater than 135º east or west of the central
meridian is trimmed.

## Example

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