The images collected by the Airshark UAS camera used local time and were 4 minutes off the equivalent GMT times logged by the navigation, so time adjustments were made as part of the geotagging (see first parameter of step 1 below). They were also processed to add USGS required information to the EXIF headers and renamed to unique file names. These steps are described here:
1) ExifTool (https://www.sno.phy.queensu.ca/~phil/exiftool/
, version 10.75) was used to geotag the images using the UAS navigation for each of the 4 flights. The conversion of the image times to GMT and 4 minute time adjustment was also accomplished in this step using this command: exiftool –AllDates+=3:56:0 -geosync=-0:4:0 -geotag "./location.gpx" *.jpg
2) ExifTool (https://www.sno.phy.queensu.ca/~phil/exiftool/
, version 10.75) was used to add required attribution tags to all the photos. The command used to update the tags was: exiftool -CopyrightNotice="Public Domain - please credit U.S. Geological Survey " -ImageDescription="Photographs of Town Neck Beach, Sandwich, Massachusetts, USA from survey 2016-043-FA " -Caption-Abstract="Town Neck Beach, Sandwich, Massachusetts, USA from survey 2016-043-FA " -Caption="Town Neck Beach, Sandwich, Massachusetts, USA from survey 2016-043-FA " -sep ", " -keywords="Town NeckBeach, Sandwich, Massachusetts, 2016-043-FA, UAS, aerial imagery, USGS " -comment="Photo from down-looking UAS camera during survey 2016-043-FA." -Credit="U.S. Geological Survey" -Contact="WHSC_data_contact@usgs.gov " -Artist="Airshark" *.JPG
3) All the JPEG images were renamed with Namexif (version 1.7, http://www.digicamsoft.com/softnamexif.html
) to ensure unique filenames and compliance with USGS Coastal/Marine Hazards and Resources Program's best practices for image naming convention. Images were renamed with a survey ID prefix followed by a local USGS UID, which corresponds to a distinct UAS project; a camera ID that distinguishes among the cameras by make, model, and camera number; the image acquisition date and coordinated universal time (UTC) in ISO8601 format; and a suffix with the original image name. For example, in this image name '2016043FA_U019AS5R_20160921T130459Z_DSC08437.JPG', 2016043FA is the survey ID, U019 is the internal identifier code, AS5R is the internal camera ID for the Airshark UAS camera, 20160921 is the date in format YYYYMMDD. A 'T' is used to separate the date from UTC time in format HHMMSS followed by a 'Z', and 'DSC08437.JPG' is the original raw photo name appended to the end of the new filename.