Interface LASHeader

Global Encoding unsigned short 2 bytes.

The meaning of GPS Time in the Point Records

• 0 (not set) -> GPS time in the point record fields is GPS Week Time (the same as previous versions of LAS).
• 1 (set) -> GPS Time is standard GPS Time (satellite GPS Time) minus 1 x 109. The offset moves the time back to near zero to improve floating point resolution.

Start of first Extended Variable Length Record - unsigned long long 8 bytes

Number of Extended Variable Length Records - unsigned long 4 bytes

File Creation Day Year unsigned short 2 bytes. 0 means no creation date

Day, expressed as an unsigned short, on which this file was created. Day is computed as the Greenwich Mean Time (GMT) day. January 1 is considered day 1.

File Creation Day Year unsigned short 2 bytes. 0 means no creation date

The year, expressed as a four digit number, in which the file was created.

Generating Software char[32] 32 bytes

Header Size unsigned short 2 bytes

The size, in bytes, of the Public Header Block itself. In the event that the header is extended by a software application through the addition of data at the end of the header, the Header Size field must be updated with the new header size. Extension of the Public Header Block is discouraged; the Variable Length Records should be used whenever possible to add custom header data. In the event a generating software package adds data to the Public Header Block, this data must be placed at the end of the structure and the Header Size must be updated to reflect the new size.

Version Major unsigned char 1 byte

Max X double 8 bytes

Max Y double 8 bytes

Max Z double 8 bytes

Version Minor unsigned char 1 byte

Min X double 8 bytes

Min Y double 8 bytes

Min Z double 8 bytes

Number of point records unsigned long 4 bytes

Number of points by return unsigned long[5] 20 bytes

Number of Variable Length Records unsigned int 4 bytes This field contains the current number of Variable Length Records. This number must be updated if the number of Variable Length Records changes at any time.

Offset to Point Data unsigned int 4 bytes

The actual number of bytes from the beginning of the file to the first field of the first point record data field. This data offset must be updated if any software adds data from the Public Header Block or adds/removes data to/from the Variable Length Records.

Point Data Format ID unsigned short 1 byte

The point data format ID corresponds to the point data record format type. LAS 1.4 defines types 0-10.

Point Data Record Length unsigned short 2 bytes

Project ID - GUID data 1 unsigned long 4 bytes. 0 means no project ID

Project ID - GUID data 2 unsigned short 2 byte. 0 means no project ID

Project ID - GUID data 3 unsigned short 2 byte. 0 means no project ID

Project ID - GUID data 4 unsigned char[8] 8 bytes. 0 means no project ID

File Signature ("LASF") char[4] 4 bytes The file signature must contain the four characters "LASF", and it is required by the LAS specification. These four characters can be checked by user software as a quick look initial determination of file type.

File Source ID unsigned short 2 bytes

File Source ID (Flight Line Number if this file was derived from an original flight line): This field should be set to a value between 1 and 65,535, inclusive. A value of zero (0) is interpreted to mean that an ID has not been assigned. In this case, processing software is free to assign any LAS 1.2 3 valid number. Note that this scheme allows a LIDAR project to contain up to 65,535 unique sources. A source can

System Identifier char[32] 32 bytes

Start of Waveform Data Packet Record - Unsigned long long 8 bytes

X offset double 8 bytes

X scale factor double 8 bytes

Y offset double 8 bytes

Y scale factor double 8 bytes

Z offset double 8 bytes

Z scale factor double 8 bytes