3DEP Lidar Base Spec News
The status of some of the Lidar Base Specification revisions has changed since the last newsletter.
Changes:
Vertical accuracy assessment using ground points: approved by ESRB
Swath Separation Images: New requirement, approved by ESRB
Swath Separation Images
This is a new requirement for delivery of Swath Separation Images. Swath separation images use color-coding to illustrate differences in elevation (z-) values where swaths overlap. They are ancillary metadata used as visual aids to more easily identify regions within point cloud datasets that may have suspect interswath alignment or other geometric issues.
Vertical Accuracy Assessment Using Ground Points
This revision modifies the method for assessing absolute vertical accuracy for both NVA and VVA to require the use of ground-classified points. The requirement that unclassified point data shall meet required VVA before further classification and processing has been removed.
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.
Clarify Unrestricted Rights Clause
The current requirement contains language specific to the US Geological Survey and mentions delivery of items not specified elsewhere. The proposed revision will remove the rights language and clarify delivery requirements.
Require Photographs of Checkpoints
Photographs will be required for checkpoints to help identify potential sources of error in the quality control process. There are currently no requirements in the Lidar Base Specification to provide photographs of checkpoints.
Clarify Class 0 and Withheld Flagging
The current text regarding Point Classification can be confusing with regard to points flagged as withheld. This revision clarifies the requirement.
Revise Swath Polygon Requirements
The current usage of swath polygons has moved beyond the requirements in LBS v.2.1. This revision brings the requirements into better agreement with usage.
Revise use of the LAS Withheld Bit Flag
Current wording of requirement is too broad and lacks clarity regarding which points must be flagged and how the bit flag relates to other classifications.