The U.S. Geological Survey (USGS) Remote Sensing Coastal Change (RSCC) project collects aerial imagery along coastal swaths with optimized endlap/sidelap and precise position information to create high-resolution orthomosaics, three-dimensional (3D) point clouds, and digital elevation/surface models (DEMs/DSMs) using Structure-from-Motion (SfM) photogrammetry methods. These products are valuable for measuring topographic and landscape change, and for understanding coastal vulnerability and response to disturbance events.
A nadir (vertical) aerial imagery survey was conducted from Cape Lookout, North Carolina to Corolla, North Carolina on August 2nd, 2020, to document pre-storm conditions in preparation for the passage of Hurricane Isaias on August 3, 2020. The observations along the coastline cover an approximately 245-kilometer-long by 300 to 700-meter-wide swath of coastline and encompass both highly developed towns as well as natural undeveloped areas, including the federal lands of Cape Lookout National Seashore and Cape Hatteras National Seashore.
Low altitude (300 meters above ground level) digital aerial imagery were acquired with a manned, fixed-wing aircraft using the "Precision Airborne Camera (PAC)" System (version 2). The PAC system is operated by C.W. Wright and consists of a mounted fixed-lens digital camera, along with a custom integrated survey-grade Global Navigation Satellite System (GNSS) receiver. Data were collected in shore-parallel lines, flying at approximately 50 meters per second (m/s) and capturing true color imagery at 1 hertz (Hz), resulting in image footprints with approximately 75-80% endlap, 60-70% sidelap, and a 5.3-centimeter (cm) ground sample distance (GSD). The precise time of each image capture (flash event) was recorded, and the corresponding aircraft position was computed during post-processing of the GNSS data. Precise image positions can then be determined by accounting for the lever arm offsets between the aircraft GNSS antenna and the camera lens, which are provided in the PAC System metadata (Kranenburg and others, 2023,
https://cmgds.marine.usgs.gov/data-services/rscc/PrecisionAirborneCameraSystem). Position data, provided as latitude/longitude/ellipsoid height, is referenced to the North American Datum of 1983 National Spatial Reference System 2011 (NAD83(2011)) coordinate system.
Each data collection is recorded in the USGS Coastal and Marine Hazards Resources Program (CMHRP) Coastal and Marine Geoscience Data System (CMGDS) field activity database and is assigned a Field Activity Number (FAN). Additional information about the field activity from which these data were derived is available online at:
https://cmgds.marine.usgs.gov/fan_info.php?fan=2020-305-CNT.
Acquisition was timed to coincide with low tide along the beach areas to ensure the maximum shoreline extent was captured. Bounding coordinates for the aerial survey are derived from the overall flight path and are not necessarily representative of the imagery coverage.
This data collection is published under the Precision Airborne Camera System data collection platform (DCP) within the RSCC Simple Data Distribution Service. This data service is structured in a folder (directory) hierarchy with subfolders corresponding to individual DCPs or groups of DCPs, which in turn contain folders with products grouped by collection effort. For more information on the RSCC Simple Data Distribution Service, refer to Ritchie and others (2023),
https://doi.org/10.5066/P9M3NYWI. For more information about the Precision Airborne Camera System DCP, refer to Kranenburg and others (2023),
https://cmgds.marine.usgs.gov/data-services/rscc/PrecisionAirborneCameraSystem/.
