| Description |
This portion of the data release presents a topographic point cloud of the intertidal zone at West Whidbey Island, WA. The point cloud was derived from structure-from-motion (SfM) processing of aerial imagery collected with an unmanned aerial system (UAS) on 2019-06-04. The point cloud has 293,261,002 points with an average point density of 1,063 points per-square meter. The point cloud is tiled to reduce individual file sizes and is grouped within a zip file for downloading. Each point in the point cloud contains an explicit horizontal and vertical coordinate, color, intensity, and classification. Water portions of the point cloud were classified using a polygon digitized from the orthomosaic imagery derived from these surveys (also available in this data release). No other classifications were performed. The raw imagery used to create these point clouds was acquired using a UAS fitted with a Ricoh GR II digital camera featuring a global shutter. The UAS was flown on pre-programmed autonomous flight lines spaced to provide approximately 70 percent overlap between images from adjacent lines. The camera was triggered at 1 Hz using a built-in intervalometer. The UAS was flown at an approximate altitude of 70 meters above ground level (AGL), resulting in a nominal ground-sample-distance (GSD) of 1.8 centimeters per pixel. Additional imagery was collected with the camera in an oblique orientation toward the coastal bluff face to image vertical faces. The raw imagery was geotagged using positions from the UAS onboard single-frequency autonomous GPS. Twenty-five temporary ground control points (GCPs) were distributed throughout the survey area to establish survey control. The GCPs consisted of a combination of small square tarps with black-and-white cross patterns and "X" marks placed on the ground using temporary chalk. The GCP positions were measured using post-processed kinematic (PPK) GPS, using corrections from a GPS base station located approximately 7 kilometers from the study area. The point clouds are formatted in LAZ format (LAS 1.2 specification). [More]
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