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LAS file format

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LAS
Filename extension
.las
Internet media typeapplication/vnd.las
Magic numberLASF
Developed byAmerican Society for Photogrammetry and Remote Sensing
Initial releaseMay 9, 2003; 22 years ago (2003-05-09)
Latest release
1.4 R15
July 9, 2019; 5 years ago (2019-07-09)
Type of formatPoint cloud data
Open format?Yes

The LAS (LASer) format is a file format designed for the interchange and archiving of lidar point cloud data. It is an open, binary format specified by the American Society for Photogrammetry and Remote Sensing (ASPRS). The format is widely used[1] and regarded as an industry standard for lidar data.[2][3]

File structure

A LAS file consists of the following overall sections:

Section Description
Public header block Describes format, number of points, extent of the point cloud and other generic data.
Variable length records (VLR) Any number of optional records to provide various data such as the spatial reference system used, metadata, waveform packet information and user application data.[1][4] Each VLR can hold a data payload of up to 65,535 bytes in length.
Point data records Data for each of the individual points in the point cloud, including coordinates, classification (e.g. terrain or building), flight and scan data, etc.
Extended variable length records (EVLR) Introduced with LAS 1.3,[5] EVLRs are similar to VLRs but are located after the point data records and allow a much larger data payload per record due to the use of 8-byte size descriptors.

Point data records

A LAS file contains point records in one of the point data record formats defined by the LAS specification; as of LAS 1.4, there are 11 point data record formats (0 through 10) available. All point data records must be of the same format within the file. The various formats differ in the data fields available, such as GPS time, RGB and NIR color and wave packet information.

The 3D point coordinates are represented within the point data records by 32-bit integers, to which a scaling and offset defined in the public header must be applied in order to obtain the actual coordinates.

As the number of bytes used per point data record is explicitly given in the public header block, it is possible to add user-defined fields in "extra bytes" to the fields given by the specification-defined point data record formats. A standardized way of interpreting such extra bytes was introduced in the LAS 1.4 specification, in the form of a specific EVLR.[4]

Derivative formats

LAZ

LAZ is an open format for lossless compression of LAS files developed by Martin Isenburg, author of its original LASzip reference implementation.[6][7][8] A LAZ file is similar in structure to the corresponding uncompressed LAS file, except the point data records are replaced by chunks of compressed point data.[9]

LASzip was originally published under the GNU LGPL, but relicensed under the Apache Public License 2.0 with the release of version 3.5.0 in 2022.[10] Alternative LAZ implementations include LAZperf[11] and laz-rs.[12]

COPC

The Cloud-Optimized Point Cloud (COPC) format specified by Hobu, Inc.[13] is a cloud-optimized variant of LAZ, analogous to the COG format's relationship to GeoTIFF.[14] A COPC file guarantees a restricted structure of the LAZ file to make its data chunks correspond to nodes in an octree, making the file suitable for subset requests.

zLAS

Esri Optimized LAS (zLAS) is a proprietary[15] format for lossless[16] LAS compression developed by Esri. While C++ headers and Windows DLLs for Esri's zLAS I/O library are available under the Apache 2.0 license,[17][18] the format specification and compressor/decompressor code are not publicly available.[19]

References

  1. ^ a b "LAS (LASer) File Format, Version 1.4". Library of Congress. 2015-01-14. Retrieved 2019-01-12.
  2. ^ "About Point Clouds and LiDAR Data". Autodesk Knowledge Network. Autodesk. 2018-05-01. Retrieved 2019-01-12.
  3. ^ "What is a LAS dataset?". Esri. Retrieved 2019-01-12.
  4. ^ a b "LAS specification, version 1.4 – R13" (PDF). American Society for Photogrammetry and Remote Sensing. 2013-07-15. Retrieved 2019-01-12.
  5. ^ "LAS specification, version 1.3 – R11" (PDF). American Society for Photogrammetry and Remote Sensing. 2010-10-24. Retrieved 2019-01-12.
  6. ^ "LASzip - free and lossless LiDAR compression". rapidlasso GmbH. Retrieved 2025-05-25.
  7. ^ Isenburg, Martin (November 2011). LASzip: lossless compression of LiDAR data (PDF) (Technical report). rapidlasso GmbH. Retrieved 2025-05-25.
  8. ^ Isenburg, Martin. "Homepage of Martin Isenburg". The University of North Carolina at Chapel Hill. Archived from the original on 2025-03-16. Retrieved 2025-05-25.
  9. ^ Eickenberg, Björn (2024-10-27). "5.1. Overview". LAZ Specification 1.4 (PDF) (Technical report). rapidlasso GmbH. Retrieved 2025-05-25.
  10. ^ "Relicence to Apache Public License 2.0". GitHub. 2022-02-01. Retrieved 2025-05-25.
  11. ^ "laz-perf". GitHub. Hobu, Inc. Retrieved 2025-05-25.
  12. ^ "laz-rs". GitHub. Retrieved 2025-05-25.
  13. ^ "Cloud Optimized Point Cloud Specification – 1.0". Hobu, Inc. 2021. Retrieved 2025-05-25.
  14. ^ "Cloud-Optimized Point Clouds (COPC)". Cloud-Optimized Geospatial Formats Guide. Cloud-Native Geospatial Foundation. Retrieved 2025-05-25.
  15. ^ "LiDAR formats". MacOdrum Library. 2024-05-31. Retrieved 2025-05-25.
  16. ^ "Esri Optimized LAS (zLAS) FAQ" (PDF). GitHub. Esri. 2015-03-13. Retrieved 2025-05-25.
  17. ^ Weitz, Lindsay (2015-03-18). "Esri Optimized LAS (zLAS) I/O Runtime Library is Now Available". ArcGIS Blog. Esri. Retrieved 2025-05-25.
  18. ^ "esri-zlas-io-library". GitHub. Esri. Retrieved 2025-05-25.
  19. ^ "LIDAR Format Letter". Open Source Geospatial Foundation Wiki. Retrieved 2025-05-25.


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