DOI: 10.5066/f7cn721h
title: Low-altitude aerial imagery and related field observations associated with unmanned aerial systems (UAS) flights over Coast Guard Beach, Nauset Spit, Nauset Inlet, and Nauset Marsh, Cape Cod National Seashore, Eastham, Massachusetts on 1 March 2016

description: Low-altitude (approximately 120 meters above ground level) digital images were obtained from cameras mounted in a fixed-wing unmanned aerial system (UAS) flown from the lawn adjacent to the Coast Guard Beach parking lot on 1 March, 2016. The UAS was a Skywalker X8 operated by Raptor Maps, Inc., contractors to the U.S. Geological Survey (USGS). Two consecutive UAS missions were flown, each with two cameras, autopilot computer, radios, and a global satellite navigation system as payload. The first flight (f1) was launched at approximately 1112 Eastern Standard Time (EST), and followed north-south flight lines, landing at about 1226 EST. Two Canon Powershot SX280 12-mexapixel digital cameras, designated rgb1 and rgb2 recorded images during this flight. The second flight (f2) was launched at 1320 EST and followed east-west flight lines, landing at 1450 EST. Prior to f2, rgb2 was replaced with a Canon SX280 modified with a Schott BG 3 filter to emphasize light at near-infrared wavelengths, designated nir1. Rgb1 and nir1 made images during this second flight. Thus four series of images were collected, designated f1_rgb1, f1_rgb2, f2_rgb1, and f2_nir1. 

Low tide on the ocean beaches was forecast for approximately 1130 EST, and estimated low tide on the marsh was at least an hour later. Weather conditions were clear and sunny during the first flight. During the second flight, there were periods with high clouds. Winds (estimated by experienced observers) during the first flight were from the north-northeast at ~15 mph, with gusts to ~20 mph. Winds decreased beginning in early afternoon, and at the end of the second flight, estimated winds were 5  10 mph with gusts to 15 mph 
USGS field technicians mapped the location of 32 ground control points and 144 independent points along cross-shore transects. These points were measured with a geographic positioning system (GPS) using real-time differential corrections from a base station set up near the launch site; they have horizontal and vertical uncertainties of approximately +/ 0.03 m. The locations of the ground control points can be used to constrain photogrammetric reconstructions based on the aerial imagery. The locations of the 144 transect points can be used for independent evaluation of the photogrammetric products. 

This data release includes the four sets of original aerial images; tables listing the image file names and locations; locations of the 140 transect points; and locations of the ground control points with photographs of the four in-place features and images showing the location of the two a posteriori points at two zoom levels. 

Collection of these data were supported by the USGS Coastal and Marine Geology Program and the USGS Innovation Center and were conducted under USGS field activity number 2016-007-FA and National Park Service Scientific Research and Collecting Permit, study number CACO-00285, permit number CACO-2016-SCI-003.