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.