True color aerial imagery from unmanned aerial systems (UAS) flights and image locations: Plum Island Estuary and Parker River NWR (PIEPR), February 27th, 2018

The Ricoh GRII HD camera used on the UAS acquires photos at 16.2 Megapixels, with file sizes generally between 4 and 6 MB on disc, depending on image complexity. Photos were collected with an ISO between 200 and 640, shutter speeds between 1/500 and 1/2500, and an aperture between 3.5 and 5. The camera was mounted on a 3DR Solo quadcopter unmanned aerial system (UAS) for each flight. Flights were flown along pre-planned lines and lasted the duration of the UAS battery life (maximum 15 minutes) or until the flight was completed or aborted. 3DR Solo includes an onboard mRo GPS (u-Blox Neo-M8N / 3DR SOLO Upgrade), which receives signals from GPS and GLONASS satellites in WGS84 (G1150) and records telemetry information including position in latitude, longitude, altitude, GPS time, pitch, roll, yaw, course, and flight mode in a telemetry log file (extension tlog), which was downloaded between each flight using file transfer protocol (FTP). The camera was set to record images at 2-second intervals, activated before takeoff, and deactivated after landing. Preflight photos of UTC time displayed on a smartphone accurate timepiece were captured with the camera and used to monitor camera clock drift.

After a flight, the SD card is removed from the camera, and all files related to the flight are downloaded and organized by flight number. A customized python program written by Seth Ackerman and Emily Sturdivant, using ExifTool by Phil Harvey (version 10.99) was used to rename image files and to update metadata in image headers. All JPEG images were renamed to ensure unique filenames and compliance with USGS Coastal/Marine Hazards and Resources Program best practices for image naming convention. Resulting filenames indicate the survey ID, flight number and camera ID, image acquisition date, and time in ISO8601 format, and the original image name (in order as listed here and separated by underscore characters). An example filename for this dataset is 2018015FA_f03r01_20180227T180757Z_P0026113.JPG, where 2018015FA is the internal survey ID, f03 is the flight number and r01 is the internal camera ID, 20180227 is the UTC date in format YYYYMMDD, A 'T' is used to separate UTC date from UTC time in format HHMMSS (180757) followed by a Z, and P0026113.JPG is the original raw photo name appended to the end of the new filename.
The following tags were updated with standardized values in the image headers to enhance the metadata available:
Artist-WHCMSC AIM Group
Credit- U.S. Geological Survey
Contact- WHSC_data_contact@usgs.gov
comment- Low-altitude aerial photograph of Plum Island, MA from survey 2018-015-FA (https://cmgds.marine.usgs.gov/fan_info.php?fa=2018-015-FA).
keywords- Plum Island, MA, 2018-015-FA, UAS, nadir, USGS, https://doi.org/10.5066/P9O9NSRK
Caption- Low-altitude aerial photograph of Plum Island, MA from survey 2018-015-FA (https://cmgds.marine.usgs.gov/fan_info.php?fa=2018-015-FA).
Copyright- Public Domain. Please credit U.S. Geological Survey
CopyrightNotice- Public Domain. Please credit U.S. Geological Survey
Caption-Abstract- Low-altitude aerial photograph of Plum Island, MA from survey 2018-015-FA (https://cmgds.marine.usgs.gov/fan_info.php?fa=2018-015-FA).
ImageDescription- Low-altitude aerial photograph of Plum Island, MA from survey 2018-015-FA (https://cmgds.marine.usgs.gov/fan_info.php?fa=2018-015-FA).
In the same customized Python program, image headers were updated with positional data from the UAS telemetry log.
First, a time consistency check was conducted between the photos and the telemetry logs. Telemetry logs recorded in Mission Planner software (version 1.3.49) and saved as GPX files were used. Photos were geotagged by adding positions from the GPX file to the images using ExifTool by Phil Harvey (version 10.99). ExifTool uses linear interpolation to determine the position of the device at the time recorded in the image. This creates values for tags GPSLatitude, GPS LatitudeRef, GPSLongitude, GPSLongitudeRef, GPSAltitude, GPSTimeStamp, GPSDateStamp.

Exiftools version 11.28 was used to extract a subset of the Exif header information to provide image location information in a separate file. The command used to extract the information is as follows:
exiftool.exe -csv -filename -GPSDateStamp -GPSTimeStamp -GPSLongitude -GPSLatitude -GPSAltitude -n fX\*.JPG > UASricoh_nav_fX.csv
where fX is the folder name which is the same as the flight number in the format fX where X is the flight number.
Once a separate file was extracted for each flight, the individual files were concatenated together (UASricoh_2018015FA_nav.csv) using the cat command in Cygwin. The VI editor was then used to remove all but the first occurrence of the header line.

Added keywords section with USGS persistent identifier as theme keyword.