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Revise Swath Polygon Requirements

By NGP Standards and Specifications

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.

 

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

Requirement in LBS v.2.1:

  • A georeferenced, polygonal representation of the detailed extents of each lidar swath collected, as a GIS layer. The goal is a set of polygons that define the area actually covered by the swaths, not merely the points collected in the swaths.

    • The extents shall be those of the actual coverage of the collected swath, exclusive of peripheral TIN artifacts. Minimum bounding rectangles or simplified rectangles are not acceptable. The boundary will generally follow the overall shape of the swath as defined by the points tagged as Edge of Flightline. Perimeter incursions into the swath, such as those caused by waterbodies, should not be followed.

    • Each swath polygon shall be attributed with the following:

      • The Project Name (string format).

      • The Start Date and Time of the swath (date for­mat, minute resolution).

      • The End Date and Time of the swath (date format, minute resolution).

      • The lift’s unique ID (string format).

      • The unique File Source ID of the swath (string format). 

      • The type of swath: “Project,” “Cross-tie,” “Fill-in,” “Calibration,” or “Other” (string format).

    • Esri polygon shapefile or geodatabase is required.

Approved change:

  • A georeferenced, polygonal representation of the detailed extents of each lidar swath collected, as a GIS layer. The goal is a set of polygons that define the area actually covered by the swaths, not merely the points collected in the swaths.

    • The extents shall be those of the actual coverage of the collected swath, exclusive of peripheral TIN artifacts:

      • Minimum bounding rectangles or simplified rectangles are not acceptable.

      • The boundary will generally follow the overall shape of the swath.

    • Each swath polygon shall be attributed with the following:

      • The lift’s unique ID (string format).

      • The type of swath (string format): 

        • "Project"

        • "Cross-tie” 

        • “Fill-in" 

        • “Calibration” or

        • “Other” 

      • Start time in adjusted GPS seconds to the nearest integer.

      • End time in adjusted GPS seconds to the nearest integer.

    • Esri polygon shapefile or geodatabase or geopackage is required. Geopackage is preferred.