Call for Input on Compression of LAS 1.4

January 21, 2014
rapidlasso GmbH, Gilching, Germany

The creators of the widely-used open source LiDAR compressor LASzip are issuing a „Call for Input“ for extending the popular LAZ format to the new point types 6 to 10 that were introduced with the LAS 1.4 specification. Their LiDAR technology company rapidlasso GmbH invites all interested parties to „The LAS room“ for an open discussion: „As LAZ has gained significant traction in the community we want to involve stakeholders across industry, academia, and government,“ so Dr. Martin Isenburg, founder of rapidlasso GmbH.

Recent conversations with large agencies suggest that LAS 1.4 is not yet being tendered and that there are no significant LAS 1.4 holdings. „So we have some time,“ says Dr. Isenburg, „No need to rush and put out a half-baked solution. I have the feeling LAS 1.4 will stay with us for a while, so we better get it right.“

The LASzip compression scheme will not change for LAS 1.X files that only contain point types 0 to 5 to guarantee „forward-compatibility“ with older, already existing LAZ readers. „The new point types,“ so Dr. Isenburg, „provide a unique opportunity to enhance the compression scheme further.“

Apart from the improvements mentioned in the LASzip journal paper, one change worth discussing is whether to encode GPS time stamps, RGBI colors, and WavePackets separately from other point attributes to allow selective reading of compressed files. Plain visualization, for example, does not need GPS time information. Another consideration is (optional) spatial indexing using LASindex. The new concept of „Appended VLRs“ in LAS 1.4 allows appending the tiny LAX files of LASindex to the end of a LAZ file.

Dr. Isenburg asks especially those who do not yet use LAZ (for technical reasons) to join „The LAS room“ and contribute suggestions: „Let’s make LASzip with LAS 1.4 support not only a better LAZ, but also your LAZ.“

LAX files contain a quadtree to describe which parts of a file have to be loaded to get all points within an area of interest
The LAX files of LASindex contain a quadtree that describes which parts of the file need to be loaded to get all points within an area of interest.

0 Kommentare zu „Call for Input on Compression of LAS 1.4“

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