| Description |
This portion of the data release presents a topographic point cloud of the Liberty Island Conservation Bank Wildlands restoration site in the Sacramento-San Joaquin Delta, derived from structure-from-motion (SfM) processing of aerial imagery collected with an Unmanned Aerial System (UAS) on 2018-10-23. The point cloud contains 380,296,568 points at an approximate point density of 323 point per square-meter. Each point contains an explicit horizontal and vertical coordinate, color, intensity, and classification. The point cloud is tiled into 500 x 500-meter tiles to reduce file size. The raw imagery used to create this point cloud was acquired using two UAS fitted with Ricoh GR II digital cameras global shutters. The UAS were flown on pre-programmed autonomous flight lines at an approximate altitude of 120 meters above-ground-level. The flight lines were oriented roughly east-west and were spaced to provide approximately 66 percent overlap between images from adjacent lines. The cameras were triggered at 1 Hz using a built-in intervalometer. The imagery was geotagged using positions from the UAS onboard single-frequency autonomous GPS. Ground control was established using twenty-four ground control points (GCPs) consisting of small square tarps with black-and-white cross patterns distributed throughout the mapping area. The GCP positions were measured using RTK GPS, with real-time corrections from a GPS base station located approximately 3 kilometers south of the study area. [More]
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