sorts the points of a LAS/LAZ/ASCII file into z-order arranged cells of a square quad tree and saves them into LAS or LAZ format. This is useful to bucket together returns from different swaths or to merge first and last returns that were stored in separate files. Alternatively lassort can sort a LAS/LAZ file in GPS time order or in a point source ID order (or first by point source IDs and then by time). For more details see the README file.