LASzip: Lossless Compression of Lidar Data

Airborne laser scanning technology (lidar) makes it easy to collect large amounts of points that sample the terrain beneath. The ASPRS LAS Specification is the standard file format for storing and distributing this data. However, managing the amount of data becomes challenging for surveys acquiring billions of points. We describe a lossless compression scheme for lidar in binary LAS format. Our compressed LAz files are only 7 to 25 percent of the original size. Our encoding and decoding speeds are several million points per second on average desk-top computers. Compression is streaming and decompression supports random-access. A reference implementation with a LGPL license is available at http://laszip.org. On a national scale, the compression savings of storing LAZ instead of LAS can be measured in Petabytes of data, i.e., data that no longer need to be hosted, backed up, and served for download. Techniques like LAszip are imperative in order to manage lidar elevation for an entire nation.