In mapmaking, a quadrilateralized spherical cube, or quad sphere for short, is an equal-area polyhedral map projection and discrete global grid scheme for data collected on a spherical surface (either that of the Earth or the celestial sphere). It was first proposed in 1975 by Chan and O'Neill for the Naval Environmental Prediction Research Facility.[2] This scheme is also often called the COBE sky cube,[3] because it was designed to hold data from the Cosmic Background Explorer (COBE) project.[4]