Geotagged low-altitude aerial imagery from unmanned aerial systems (UAS) flights over of the Lake Ontario shoreline in the vicinity of Sodus Bay, New York, in July 2017

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 1/1000, and an apera ture between 3.5 and 4.5. Ricoh cameras do no contain an internal GPS, and an external GPS mounted on the UAS is used to add geopositioning information during post-processing (described later). The camera was mounted on a 3DR Solo quadcopter unmanned aerial system (UAS; FAA number- FA3R4LWWY9) 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. 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. Camera time and UTC time were never different (to a 1 second accuracy) during this survey. However, the GPS data was processed in local (EST) time and the camera was recording in UTC, therefore a 14400 second correction was applied (explained in the next process step).

The JPEG images were geotagged by adding location information to standard GPS tags (GPSLatitude, GPSLatitudeRef, GPSLongitude, GPSLongitudeRef, GPSAltitude, GPSTimeStamp, GPSDateStamp) in the EXIF headers. Image descriptions, Artist credit, Copyright, caption information, keywords, and credits/origin tags were also added, and the images were renamed. All of the following process steps were conducted by the same person using pyExifToolGUI (version 0.50), ExifTools (version: 10.61), and Namexif (version 1.7).
1. Telemetry logs recorded in Mission Planner software (version 1.3.49) and saved as GPX files were used in pyExifToolGUI to geotag the JPEG photos. PyExifTool provides a graphical frontend for ExifTools and only requires 3 user inputs to complete geotagging the raw photos. Geotagging was completed per flight since there was a single .gpx file and image folder file per flight. In pyExifTool under the 'Edit Data' tab, Geotagging is selected and the user supplies the folder containing the images to be geotagged, the GPS log file (a GPX file for this survey), and a Geosync time to account for any offset between the GPS and camera. A Geosync time of -14400 sec was supplied here for all 2017-042-FA flights, because GPS time was processed in EST, which is 4 hours or 14400 sec behind UTC time. There was no other 'time drift' difference noted during the survey between the camera and the GPS clocks.
2. After all the JPEG photos were geotagged in pyExifToolGUI, ExifTools was used to update several additional tags for all the photos. The updated tags include: -CopyrightNotice, -ImageDescription, -Caption-Abstract, -Caption, -keywords, -comment, -Credit, -Contact, -Artist
JPEG tags:

Comment: Photographs of the Lake Ontario shoreline, Sodus Bay vicinity, New York, USA from survey 2017-042-FA.

EXIF tags:

ImageDescription: Photographs of the Lake Ontario shoreline, Sodus Bay vicinity, New York, USA from survey 2017-042-FA.
Artist: Sandy Brosnahan
Copyright: Public Domain - please credit U.S. Geological Survey

IPTC tags:

Credit: U.S. Geological Survey
Contact: WHSC_data_contact@usgs.gov
Keywords: Lake Ontario / New York / 2017-042-FA / UAS / aerial imagery / USGS
CopyrightNotice: Public Domain - please credit U.S. Geological Survey
Caption-Abstract:  Photographs of the Lake Ontario shoreline, Sodus Bay vicinity, New York, USA from survey 2017-042-FA.

XMP tags:

Caption: Photographs of the Lake Ontario shoreline, Sodus Bay vicinity, New York, USA from survey 2017-042-FA.

3. Finally, 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 and Marine Geology 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 USGS cameras by make, model, and camera number; the image acquisition date and time in ISO8601 format(UTC; and a suffix with the original image name. For example, image name '2017042FA_U036RI01_20170714T162904Z_A2018661.JPG', 2017042FA is the internal survey ID, U036 is the internal UID, RI01 is the internal camera ID, 20170714 is the UTC date in format YYYYMMDD. A 'T' is used to separate UTC date from UTC time in format HHMMSS followed by a Z, and A2018661 is the original raw photo name appended to the end of the new filename.

Added keywords section with USGS persistent identifier as theme keyword.