Directory of Map Projections

What is a projection?

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HEALPix

Parameters: Peaks: 1 ≤ H ≤ 12

Classifications

pseudocylindric
interrupted
equal-area

Graticule

Meridians: Straight lines, vertical up to the latitude of interruption; thence diagonal.
Parallels: Equally spaced straight parallel lines. Perpendicular to the central meridian.
Poles: Each pole is represented by points with a count of H.
Symmetry: About the central meridian and the equator.

Scale

Dependent on parameterization.

Distortion

Dependent on parameterization.

Parameters

H, the number of segments the high latitudes are split into.

Usage

Parameterized with H=4, K=3, the projection has been widely used in cosmology for representing data pertaining to the cosmic microwave background.

Origin

Devised by Krzysztof M. Górski of the Theoretical Astrophysics Center in Copenhagen, Denmark, in 1997, and presented in 1998. The name is an acronym for Hierarchical Equal Area isoLatitude Pixelisation. The projection uses a cylindric equal-area for the low latitudes and Collignon for the interrupted parts.

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