equal-area projection
See Also: projection
[map projections] A projection in which the whole of the map as well as each part has the same proportional area as the corresponding part of the earth.
Cylindrical Equal-Area Projection
The map projection having transformation equations
(1) ...
A Lambert azimuthal equal-area projection of the Earth.
The Lambert azimuthal equal-area projection, or Lambert azimuthal projection, is an equal-area map projection.
Equal-Area
correctly shows the size of a feature
Conformal
correctly shows the shape of features (A map can not be both equal-area or conformal - it can only be one; or the other; or neither.) ...
Equal-area Conic Projections by Lambert and Albers
Map in Albers's conic projection, rendered with standard parallels 60°N and 30°N; reference parallel 45°N, central meridian 0° ...
Albers Equal-Area Conic Projection(Albers)
With standard parallels of 29.5 and 45.5 degrees, this projection is one commonly used to depict the United States. It was used by the USGS in their 1970 National Atlas.
equal-area projection
A projection in which the whole of the map as well as each part has the same proportional area as the corresponding part of the earth. An equal-area projection may distort shape, angle, scale, or any combination thereof.
Area: Equal-area.
Direction: True direction radiating from the central point.
Distance: True at center. Scale decreases with distance from the center along radii and increases from the center perpendicular to the radii.
Suitable equal-area projections for distribution maps include those developed by Lambert, whether azimuthal, cylindrical, or conical. These do, however, have rather noticeable shape distortions.
Sinusoidal equal-area maps have straight parallels at right angles to a central meridian. Other meridians are sinusoidal curves. Scale is true only on the central meridian and the parallels.
Sinusoidal Equal-Area Projection Map projection that represents areas in their true form on a two-dimensional map. Distances are only correct along parallels and central meridian.
Equal-area grid atlases based on systematic regional surveys are also easily converted to a raster GIS. The raster is a flexible structure for data storage, sampling, cross-validation, spatial analysis, modeling, and display. McAllister et al.
Maps that accurately reflect area are often called equal-area maps (an example is the Albers equal-area conic map). Maps that maintain the shape of objects are called conformal.
A map projection is said to be equal-area or equivalent if it portrays areas over the entire map so that they retain the same proportional relationship to the areas on the Earth they represent.
Equal-area projections do not distort the size of areas but do distort their shapes. Conformal projections are those on which the scale is the same in any direction at any point on the map.
(This scale is only useful on equal-area map projections.) So, on a map with a RF of 1:24,000, 1 inch on the map represents 24,000 inches. We can think of this as 1 inch = 24,0000 inches.
The last of the basic conic projections (fig.3.16) to be developed with one of the three major properties of conformality, equivalence or equidistance along meridians was this equal-area presented by H.C.
1. Define the three standard properties of map projections: equal-area, equidistant and conformal. Discuss the relative importance of each for different applications. What types of applications require which properties?
A conformal projection primarily preserves shape, an equidistant projection primarily preserves distance, and an equal-area projection primarily preserves area.
These images show the earth using several different projections: ...
Even when the data were accurately obtained, their projection can introduce distortions. Use equal-area projections for area measurements that need high accuracy. Use projections which locally have small length distortions for distance measurements.
Earth, it also has a projection, a way of translating the three-dimensional real surface of the geoid to a two-dimensional picture. The most commonly used is the Mercator Projection; other popular projections are polar and a variety of equal-area ...
Conformal projections preserve angular relationships, and better preserve arc-length, while equal-area projections are more appropriate for statistical studies and work in which the amount of material is important.
Equal-area projections, such as the Goode homolosine, typically have non-straight longitudes and may have unusual outlines.
 See also: Map, Area, Projection, Map Projection, Parallel
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