Snyder equal-area projection is a

polyhedral map projection A polyhedral map projection is a map projection based on a spherical polyhedron. Typically, the polyhedron is overlaid on the globe, and each face of the polyhedron is transformed to a polygon or other shape in the plane. The best-known polyhedral ...

used in the '' ISEA (Icosahedral Snyder Equal Area)

discrete global grid A discrete global grid (DGG) is a mosaic that covers the entire Earth's surface. Mathematically it is a space partitioning: it consists of a set of non-empty regions that form a partition of the Earth's surface. In a usual grid-modeling strate ...

s''. It is named for John P. Snyder, who developed the projection in the 1990s. Snyder, J. P. (1992), “An Equal-Area Map Projection for Polyhedral Globes”, Cartographica, 29(1), 10-21
urn:doi:10.3138/27H7-8K88-4882-1752
It is a modified

Lambert azimuthal equal-area projection The Lambert azimuthal equal-area projection is a particular mapping from a sphere to a disk. It accurately represents area in all regions of the sphere, but it does not accurately represent angles. It is named for the Swiss mathematician Johann ...

, most often applied to a polyhedral globe consisting of an

icosahedron In geometry, an icosahedron ( or ) is a polyhedron with 20 faces. The name comes and . The plural can be either "icosahedra" () or "icosahedrons". There are infinitely many non- similar shapes of icosahedra, some of them being more symmetrica ...

. PROJ guide's "Icosahedral Snyder Equal Area"
proj.org/operations/projections/isea.html
D. Carr ''et al.'' (1997),
ISEA discrete global grids
; in "Statistical Computing and Statistical Graphics Newsletter" vol. 8. DualTiling-TriangHex-fig1

Use in the ISEA model

As stated by Carr at al. article, page 32: : ''The S in ISEA refers to John P. Snyder. He came out of retirement specifically to address projection problems with the original EMAP grid (see Snyder, 1992). He developed the equal area projection that underlies the gridding system. : : ''ISEA grids are simple in concept. Begin with a Snyder Equal Area projection to a regular icosahedron (...) inscribed in a sphere. In each of the 20 equilateral triangle faces of the icosahedron inscribe a hexagon by dividing each triangle edge into thirds (...). Then project the hexagon back onto the sphere using the Inverse Snyder Icosahedral equal area projection. This yields a coarse-resolution equal area grid called the resolution 1 grid. It consists of 20 hexagons on the surface of the sphere and 12 pentagons centered on the 12 vertices of the icosahedron.''

References

{{cartography-stub Equal-area projections