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chunkA primar (resolved)chunk is composed of a set of touching but non-overlapping primary segments (or parts of segments) which fills a "chunk" of a stave, and is therefore bounded on the east and west by lines of constant mu, and north-south by lines of constant eta (if in the North). Southern chunks have no eta boundary applied. A chunk may also have a lambda cut if it is at the end of the survey region for that stripe. Primary chunks do not overlap, so the union of all existing chunks represents the unique sky coverage for the survey at any given time. Note that the bounds on chunks, if using mu/eta, are a mix of survey coordinates and great circle coordinates. Note: The term chunk has sometimes been used to describe an area of sky that has had tiling run on it. This is properly called a TileRun. In general chunks contain overlapping areas which are counted multiple times unless the primary or resolved area is indicated.