LAS Format Elements

Author:Mateusz Loskot
Contact:mateusz at loskot dot net

On this page, elements and attributes of LAS Format 1.0 and 1.1 are compared.

See also

The LAS 1.0-1.3 Permuation matrix contains a detailed description of LAS header and point discrepancies between versions in addition to this (older) document.

Data Types

Both versions of LAS Format Standard define and use the same set of data types and their sizes:

  • 1 byte
    • char (int8_t)
    • unsigned char (uint8_t)
  • 2 bytes
    • short (int16_t)
    • unsigned short (uint16_t)
  • 4 bytes
    • long (int32_t)
    • unsigned long (uint32_t)
  • 8 bytes
    • double - double precision floating-point number (64-bit) as defined in IEEE 754 Standard

Public Header Block

# Element LAS 1.0 LAS 1.1
1 File Signature (“LASF”) int8_t[4], required
2 File Source ID   uint16_t, required
3 Reserved uint32_t uint16_t
4 GUID data 1 (Project ID) uint32_t
5 GUID data 2 (Project ID) uint16_t
6 GUID data 3 (Project ID) uint16_t
7 GUID data 4 (Project ID) uint8_t[8]
8 Version Major uint8_t, required
9 Version Minor uint8_t, required
10 System identifier int8_t[32], required
11 Generating software int8_t[32], required
12 Flight date Julian / Day of Year uint16_t
13 Year uint16_t
14 Header size uint16_t, required
15 Offset to data uint32_t, required
16 Number of variable length records uint32_t, required
17 Point data format ID (0-99) uint8_t, required
18 Point data record length uint16_t, required
19 Number of point records uint32_t, required
20 Number of points by return uint32_t[5], required
21 X scale factor double, required
22 Y scale factor double, required
23 Z scale factor double, required
24 X offset double, required
25 Y offset double, required
26 Z offset double, required
27 Max X double, required
28 Min X double, required
29 Max Y double, required
30 Min Y double, required
31 Max Z double, required
32 Min Z double, required
Total number of bytes: 227 227

Type specifier of the form of type[N] where N is a number, represents array of N elements of type.

Point Data

The table below is based on definition of Point Data Record Format 0 and it does not include what’s specified Point Data Record 1.

# Element LAS 1.0 LAS 1.1
1 X int32_t, required
2 Y int32_t, required
3 Z int32_t, required
4 Intensity uint16_t
5 Return number 3 bits (0,1,2), required
6 Number of returns (given pulse) 3 bits (3,4,5), required
7 Scan direction flag 1 bit (6), required
8 Edge of flight line 1 bit (7), required
9 Classification uint8_t uint8_t, required
10 Scan angle rank (-90 to +90) int8_t, required
11 File Marker / User Data (1) uint8_t
12 User Bit Field / Point Source ID (2) uint16_t uint16_t, required
  1. FileMarker from 1.0 has been renamed to User Data in 1.1 and is available for any use.
  2. User Bit Field from 1.0 has been renamed to Point Source ID in 1.1 and marked as required.