NGP Standards and Specifications

Update LAS reference to R15

There are currently eleven (11) references to LAS v.1.4-R13 in the Lidar Base Specification v. 2.1. All of these will be updated to LAS v.1.4-R15.

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Status of this revision: Published in Lidar Base Specification 2020 rev. A

Background:

The reference to the LAS specification is outdated and needs to be changed to the most recent version.

Current references to R-13 that will be updated to R-15:

Collection Requirements

The intensity values recorded in the LAS files shall be normalized to 16 bit, as required by the LAS specification version 1.4–R13 (ASPRS, 2011).

Data Processing and Handling

ASPRS LAS File Format
All point deliverables shall be in LAS format, version 1.4-R13, using Point Data Record Format 6, 7, 8, 9, or 10. Data producers are encouraged to review the LAS specification version 1.4–R13 in detail (ASPRS, 2011).
Full Waveform
LAS deliverables, including waveform data, shall use external auxiliary files with the extension .wdp to store waveform packet data. See LAS specification version 1.4–R13 (ASPRS, 2011).
Time of Global Positioning System Data
GPS data shall be recorded as Adjusted GPS Time (Standard [satellite] GPS time minus 1*10^9) at a precision sufficient to allow unique timestamps for each pulse.
Well-Known Text
ALL entries shall be tagged as “Superseded”—EXCEPT for the single valid entry to be used. See LAS specification version 1.4–R13 (ASPRS, 2011) for further details.
File and Point Source Identification
The file source ID for tiled LAS files shall be set to '0' (see LAS specification version 1.4–R13 [ASPRS, 2011]).
Use of the LAS Withheld Bit Flag
Outliers, blunders, geometrically unreliable points near the extreme edge of the swath, and any other points the data producer deems unusable are to be identified using the withheld bit flag, as defined in LAS specification version 1.4–R13 (ASPRS, 2011).
Point Classification
If it is necessary to identify overage points in overlap areas, the overage points shall be identified using the overlap bit flag as defined in LAS Specification Version 1.2-R13 (ASPRS, 2011).
Model key points, if calculated, shall be identified using the key point bit flag as defined in LAS specification version 1.4–R13 (ASPRS, 2011). Model key points may, in addition, be identified using class 8 at the discretion of the data producer.

Deliverables

Classified Point Data
If collected, waveform data in external auxiliary files with the extension .wdp. See LAS specification version 1.4–R13 (ASPRS, 2011) for additional information.
Intensity values, normalized to 16-bit. See LAS specification version 1.4–R13 (ASPRS, 2011) for additional information.

References

American Society for Photogrammetry and Remote Sensing (ASPRS), 2011, LAS specification (ver. 1.4–R13, July 2013): Bethesda, Md., American Society for Photogrammetry and Remote Sensing, 27 p. [Also available at http://www.asprs.org/wp-content/uploads/2010/12/LAS_1_4_r13.pdf.]