Low-altitude aerial imagery collected from a Helikite at Head of the Meadow Beach, Truro on March 10, 2022

These JPEG images were collected with a camera (Sony a6000) wired to the GNSS receiver 15 cm vertically offset from the focal point and hung from the Helikite (2022015FA_Truro_HelikiteCameraAttachment_browse.JPG) so that the camera faced downward. The Helikite was on a 60 m string and kitesurfing harness; together the Helikite and gear were walked up and down the beach to achieve overlapping images. The horizontal positions and elevations of each image (2022015FA_Truro_photolocations.csv) were recorded from the GNSS receiver (EMLID Reach M2) and processed in PPK mode using the MASS CORS network. The navigation data was added to the image EXIF information after the flight as described in the process steps. It is recommended when using the imagery for photogrammetric purposes to also use the ground control point locations (see larger work citation Navigation: 2022015FA_Truro_nav_GCPs.csv). Photos were downloaded and adjusted in Adobe Lightroom Classic for brightness due to the changing cloud conditions.

The GNSS navigation data was processed in Inertial Explorer (https://novatel.com/products/waypoint-software/inertial-explorer, version 8.70.8722). The positions were processed in the NAD83(2011) datum, which provided the Latitude, Longitude, and Ellipsoid attributes. Then Geoid 12B was applied using NAVD88 as the vertical datum and UTM Zone 19N for the horizontal coordinate reference system to produce the Northing, Easting, and Altitude attributes. The GPS offset was not accounted for in this step, so the offset should be accounted for when deriving other products. All of the attributes here are provided in the 2022015FA_Truro_f1_photolocations.csv but only the latitude, longitude, and altitude (NAVD88) were embedded in the image header.

The images acquired with the camera were geotagged and processed to add additional information required by the USGS to the EXIF headers using ExifTools (https://exiftool.org/, version: 12.06), and the files were renamed to a unique identifier using Namexif (http://www.digicamsoft.com/softnamexif.html, version 2.1) to avoid any possibility of duplicate names. These steps are described here. 1. Using the GNSS navigation from the previous step, ExifTools was used to tag each photo with the following tags: Credit, Copyright, UsageTerms, ImageDescription, Artist, GPSAreaInfo, GPSMapDatum, GPSLatitude, GPSLongitude, and GPSAltitude stored in a csv file with the command:' -exiftool -csv="C:\directory\name\Geotags_EXIF.csv" C:\directory\name\of\photos *.jpg The first row of the CSV are the tag names; the first column is SourceName (unique image names). Keywords were added with the following command in the directory with all the photographs: exiftool -keywords="aerial imagery" -keywords="Head of the Meadow Beach" -keywords=Massachusetts -keywords="2022-015-FA" -keywords=USGS -overwrite_original *.jpg To read out the photo information to a csv when in the directory with the photos, the command is: exiftool -csv *.JPG > directory/name/allheaders_out.csv 2. All the JPEG images were renamed with Namexif (https://us.digicamsoft.com/softnamexif.html v 2.2 accessed April 2020) to ensure unique filenames and compliance with the USGS Coastal and Marine Hazards and Resources Program's best practices for image naming convention. Images were renamed with the field survey ID prefix; flight number, and ID that distinguishes USGS cameras by make/camera number, the image acquisition date, coordinated universal time (UTC) in ISO8601 format, and a suffix with the original image name. For example, image name '2022015FA_f01s6000_20220310T165822Z_image####.jpg', 2022015FA is the survey ID, f01 is the flight number, s6000 is the camera make (SONY) and model (6000), and 20220310 is the UTC date in the format YYYYMMDD. A 'T' is used to separate UTC date from UTC time in format HHMMSS followed by a Z, and image####.jpg is the original raw photo name appended to the end of the new filename. Because the camera time was collected in EST the time in Namexif was shifted +4:00:00 to be in UTC.