LAS FORMAT VERSION 1.2:
This document reflects the second revision of the LAS format specification since its initial version
1.0 release. Version 1.2 retains the same structure as version 1.1 including identical field
alignment. LAS 1.1 file Input/Output (I/O) libraries will require slight modifications in order to
be compliant with this revision. A LAS 1.1 Reader will read LAS 1.2 (without the new
enhancements) with no modifications.
A detailed change document that provides both an overview of the changes in the specification
as well as the motivation behind each change is available from the ASPRS website in the LIDAR
committee section.
The additions of LAS 1.2 include:
• GPS Absolute Time (as well as GPS Week Time) – LAS 1.0 and LAS 1.1 specified GPS
“Week Time” only. This meant that GPS time stamps “rolled over” at midnight on
Saturday. This makes processing of LIDAR flight lines that span the time reset difficult.
LAS 1.2 allows both GPS Week Time and Absolute GPS Time (POSIX) stamps to be used.
• Support for ancillary image data on a per point basis. You can now specify Red, Green,
Blue image data on a point by point basis. This is encapsulated in two new point record
types (type 2 and type 3).
LAS FORMAT DEFINITION:
The LAS file is intended to contain LIDAR point data records. The data will generally be put into
this format from software (e.g. provided by LIDAR hardware vendors) which combines GPS, IMU,
and laser pulse range data to produce X, Y, and Z point data. The intention of the data format is
to provide an open format that allows different LIDAR hardware and software tools to output
data in a common format.
The format contains binary data consisting of a header block, Variable Length Records, and point
data.
PUBLIC HEADER BLOCK
VARIABLE LENGTH RECORDS
POINT DATA RECORDS
All data is in little-endian format. The header block consists of a public block followed by Variable
Length Records. The public block contains generic data such as point numbers and coordinate
bounds. The Variable Length Records contain variable types of data including projection
information, metadata, and user application data.
DATA TYPES:
The following data types are used in the LAS format definition.
• char (1 byte)
• unsigned char (1 byte)
• short (2 bytes)
• unsigned short (2 bytes)
LAS 1.2
2
