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Tim suggested that at the hit level a pixel detector should return a cellID that is a single int, not a pair. This is converted to (u,v) in local coordinates by a method of the geometry system. One good case to illustrate why this is a good idea is the case of a hexagonal close packed pixel detector, in which the transformation from a cellID, whether 1D or 2D, into (u,v) is complicated and should be hidden from the user. Another case is a strip detector with strips that are not simple rectangles, such as curved strips or phi strips that have
a width that is a function of radius. So Rob will modify his proposed classes to be consistent with this idea.
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