Geotagged lakebed images and their locations collected in the vicinity of Buffalo Reef, Michigan, within Lake Superior during USGS Field Activity 2021-005-FA using the USGS MiniSEABOSS (JPEG images, point shapefile; GCS WGS 84)

PROCESSING STEP 1:COLLECTED DATA.
A geophysical and geological sampling survey (field activity 2021-005-FA) was conducted in Lake Superior, Michigan, in August 2021. The R/V Rafael occupied preselected target sites, and the MiniSEABOSS was deployed off the vessel's port side from a davit just aft of the cabin. The MiniSEABOSS was equipped with a modified Van Veen grab sampler, Canon PowerShot G12 digital still camera, an independent strobe, an oblique downward-looking monochrome video camera with a topside feed and a dive light to illuminate the lakebed for photograph collection. The elements of this particular MiniSEABOSS were held within a stainless-steel frame that measured ~1 x 1 meter. The frame had a stabilizer fin that oriented the system as it drifted over the lakebed. Two red lasers were set 20 centimeters apart (both as they were mounted on the MiniSEABOSS frame and as seen in photographs and video on the lake) for scale measurements. The red laser dots can usually be seen in the lakebed photos depending on the bottom type and distance to the bottom. The winch operator lowered the MiniSEABOSS until the lakebed was observed in the topside live video feed. Generally, the vessel and MiniSEABOSS drifted with wind and current for up to a few minutes to ensure a decent photo with a clear view of the lakebed was acquired. The Canon camera was triggered manually by an operator watching the video stream. The photographed area is usually 0.5 to 1.25 meters (across) from left to right. Bottom video used to guide the photo-taking and avoid obstacles was not recorded. Fourteen sites did not have any usable photographs. After photographs were taken, the winch operator lowered the Van Veen grab sampler until it rested on the bottom. When the system was raised, the Van Veen grab sampler closed and collected a sample as it was lifted off the lakebed. The sampler was recovered to the deck of the survey vessel where a photograph of the sample in the Van Veen grab was taken. Then a subsample was taken for grain-size analysis at the sediment laboratory at the USGS Woods Hole Coastal and Marine Science Center. During the survey, DGPS navigation from a Hemisphere R131 DGPS receiver was logged through a serial connection to a computer running the Global Mapper software package to visualize and record the vessel's spatial location throughout the sampling survey. The DGPS was set to receive fixes at a 1-second interval in geographic coordinates (WGS 84). Dates and times were recorded in UTC. Log files were saved for each survey in NMEA text format.

PROCESSING STEP 2: IDENTIFIED CAMERA TIME OFFSETS FOR THE CANON PHOTOS.
The original JPEG images do not represent spatial data; however, they were geotagged in a subsequent process step by linking the time the image was taken, which was recorded in the metadata embedded in the header of each JPEG image, to the corresponding time in the navigation file. Before geotagging the images, the Canon camera time, which was set to UTC, was compared to the GPS time using calibration photos to see if a time offset should be applied to the camera time of the photos. Camera time drift and the precision with which the camera time can be set often result in a time offset; sometime the camera is just way off and it easier to adjust in post-processing. The calibration photographs indicated that the Canon camera time was more than 40 minutes ahead of GPS time, therefore it was noted that a total correction value of 2504 seconds was need and corrected for in a later process step.

Step 3: Culled the photos.
A several of the photos had no corresponding navigation data and were removed from the dataset. These photos were often ones taken on deck or in the water column. Many other bottom photographs did not have a clear view of the lakebed or were otherwise obscured and were therefore culled to select a few representative images for each site for publication. The selected photos were then reviewed to choose representative photos with a clear view of the lakebed.

Step 4: Geotagged the photos.
To geotag the images, the following commands were used with ExifTool (version 12.00) to populate the GPS tags (GPSLatitudeRef, GPSLatitude, GPSLongitudeRef, GPSLongitude, GPSTimeStamp, and GPSDateStamp) in the metadata embedded in the header of each JPEG image. Different commands were run for each day's images because each day had its own NMEA navigation file.
Photos from Julian day 227: exiftool -api GeoMaxIntSecs=2 -api GeoMaxExtSecs=0 -P -geotag ../../SEABOSS_nav/Hemisphere_jd227.nmea -geosync=-2504 '-geotime<${DateTimeOriginal}+00:00' -overwrite_original *.JPG
Photos from Julian day 228: exiftool -api GeoMaxIntSecs=2 -api GeoMaxExtSecs=0 -P -geotag ../../SEABOSS_nav/Hemisphere_jd228.nmea -geosync=-2504 '-geotime<${DateTimeOriginal}+00:00' -overwrite_original *.JPG
Photos from Julian day 229: exiftool -api GeoMaxIntSecs=2 -api GeoMaxExtSecs=0 -P -geotag ../../SEABOSS_nav/Hemisphere_jd229.nmea -geosync=-2504 '-geotime<${DateTimeOriginal}+00:00' -overwrite_original *.JPG
In the above commands, the "-api GeoMaxIntSecs" option sets the maximum interpolation time to 0 seconds for geotagging. The "-api GeoMaxExtSecs" option sets the maximum extrapolation time to 0 seconds for geotagging. The "-P" option preserves the FileModifyDate. The "-m" option ignores a warning given by ExifTool when reading or writing a file containing unknown MakerNotes. If this option is not used, the following warnings are issued since ExifTool does not recognize the MakerNotes in some types of images: "Warning: [minor] Unrecognized MakerNotes; Warning: [minor] Maker notes could not be parsed." The "-geosync" option is used when the image timestamps are not properly synchronized with the GPS time and is equal to the time offset identified in a previous process step; it is the time difference in seconds that is added to the camera time before determining the image's GPS time and location with a leading "+" or "-" added for positive or negative differences (negative if the camera clock was ahead of the GPS time). Finally, the "-geotime<${DateTimeOriginal}+00:00" argument is added to geotag images for which the camera clock was set to UTC. For more information about the ExifTool commands, see https://exiftool.org/geotag.html and https://exiftool.org/faq.html.

Step 5: Incorporated survey information into the photos' header metadata.
Additional survey information was incorporated into the metadata embedded in the header of each JPEG image. Images may have different metadata formats embedded in their headers, and the commands below incorporated survey information into the following three image metadata formats: Exchangeable image file format (Exif), International Press Telecommunications Council (IPTC), and Extensible Metadata Platform (XMP). The second command below duplicates values from Exif and IPTC metadata tags to XMP tags because various software packages read different tags. Please note that only a subset of these tags may be accessed depending on the software used to view the image metadata.
Command to incorporate survey information into the metadata embedded in the header of each JPEG image using ExifTool (version 12.00):
exiftool -P -IPTC:Credit="U.S. Geological Survey" -IPTC:Contact="WHSC_data_contact@usgs.gov" -EXIF:Copyright="Public Domain" -XMP:UsageTerms="Unless otherwise stated, all data, metadata and related materials are considered to satisfy the quality standards relative to the purpose for which the data were collected. Although these data and associated metadata have been reviewed for accuracy and completeness and approved for release by the U.S. Geological Survey (USGS), no warranty expressed or implied is made regarding the display or utility of the data for other purposes, nor on all computer systems, nor shall the act of distribution constitute any such warranty." -EXIF:ImageDescription="https://cmgds.marine.usgs.gov/fan_info.php?fa=2021-005-FA - Lake bed photograph from the USGS mini-SEABOSS in Lake Superior, Keweenaw Peninsula, Michigan during survey 2021-005-FA" -XMP:AttributionURL="TBD" -EXIF:GPSAreaInformation="position post-processed with data from ship's navigation data" -EXIF:GPSMapDatum="EPSG:4326 (WGS 84)" -EXIF:Artist="WHCMSC Sea Floor Mapping Group" -overwrite_original *.JPG
Command to duplicate metadata from the Exif and IPTC formats to XMP using ExifTool:
exiftool -P -m "-XMP-photoshop:Credit<IPTC:Credit" "-XMP-iptcCore:CreatorWorkEmail<IPTC:Contact" "-XMP-dc:Rights<EXIF:Copyright" "-XMP-dc:Description<EXIF:ImageDescription" "-XMP-exif:all<GPS:all" "-XMP-exif:GPSLatitude<Composite:GPSLatitude" "-XMP-exif:GPSLongitude<Composite:GPSLongitude" "-XMP-exif:GPSDateTime<Composite:GPSDateTime" "-XMP-photoshop:DateCreated<EXIF:DateTimeOriginal" "-XMP-xmp:ModifyDate<EXIF:ModifyDate" "-XMP-dc:Creator<EXIF:Artist" "-XMP-tiff:Make<EXIF:Make" "-XMP-tiff:Model<EXIF:Model" -overwrite_original *.JPG
The following metadata tags were populated in the JPEG image header using the above ExifTool commands:
Exif tags and the information used to populate these tags:
Artist: Woods Hole Coastal and Marine Science Center (WHCMSC) Sea Floor Mapping Group (SFMG) Copyright: Public Domain GPSAreaInformation: position post-processed with data from the ship's navigation system GPSMapDatum: EPSG:4326 (WGS 84) ImageDescription: https://cmgds.marine.usgs.gov/fan_info.php?fa=2021-005-FA - Lake bed photograph from the USGS MiniSEABOSS in Lake Superior, Keweenaw Peninsula, Michigan during survey 2021-005-FA
IPTC tags and the information used to populate these tags:
Contact: WHSC_data_contact@usgs.gov Credit: U.S. Geological Survey
XMP tags and the information used to populate these tags:
AttributionURL: https://doi.org/10.5066/P9NJY125 Creator: duplicated from Exif Artist CreatorWorkEmail: duplicated from IPTC Contact Credit: duplicated from IPTC Credit DateCreated: duplicated from Exif DateTimeOriginal Description: duplicated from Exif ImageDescription GPSAreaInformation: duplicated from Exif GPSAreaInformation by copying all the Exif GPS tags to the same-named tags in XMP (-XMP-exif:all<GPS:all) GPSDateTime: duplicated using the composite of Exif GPSDateStamp and Exif GPSTimeStamp GPSLatitude: duplicated using the composite of Exif GPSLatitude and Exif GPSLatitudeRef GPSLongitude: duplicated using the composite of Exif GPSLongitude and Exif GPSLongitudeRef GPSMapDatum: duplicated from Exif GPSMapDatum by copying all the Exif GPS tags to the same-named tags in XMP (-XMP-exif:all<GPS:all) Make: duplicated from Exif Make Model: duplicated from Exif Model ModifyDate: duplicated from Exif ModifyDate PreservedFileName: original image file name, which is unique for each image Rights: duplicated from Exif Copyright UsageTerms: Unless otherwise stated, all data, metadata and related materials are considered to satisfy the quality standards relative to the purpose for which the data were collected. Although these data and associated metadata have been reviewed for accuracy and completeness and approved for release by the U.S. Geological Survey (USGS), no warranty expressed or implied is made regarding the display or utility of the data for other purposes, nor on all computer systems, nor shall the act of distribution constitute any such warranty.
To extract the geotagging and survey information (except for the duplicated tags) from the image metadata using ExifTool, the following command can be used (tested with ExifTool version 12.00):
exiftool -csv -filename -EXIF:GPSTimeStamp -EXIF:GPSDateStamp -GPSLatitude -GPSLongitude -n -IPTC:Credit -IPTC:Contact -EXIF:Copyright -XMP:UsageTerms -EXIF:ImageDescription -XMP:AttributionURL -EXIF:GPSAreaInformation -EXIF:GPSMapDatum -EXIF:Artist *.JPG > out.csv
The "-csv" option writes the information to a CSV file. The "-n" option formats the latitude and longitude as signed decimal degrees. Please note that the above command was tested on macOS; Windows users may need to use "exiftool.exe" instead of "exiftool."

Step 6: Renamed the images.
Then images were renamed to include the field activity identifier, and GPS date and time in the ISO 8601 standard (YYYYMMDD T [time separator] HHMMSS Z [Zulu/UTC time]) in the filename. Renaming the images was done by creating a shell script with the original image name and the new filename with the GPS date and time information parsed from the image's Exif metadata tags using exiftool (version 12.30).
exiftool -csv *.JPG -GPSTimeStamp -GPSDateStamp | awk -F, '{split($1,a,"_"); split($2,t,":"); split($3,d,":");print "mv -v "$1" 2021-005-FA_"d[1]d[2]d[3]"T"t[1]t[2]t[3]"Z_"a[1]"_"a[2]}' | sh

Step 7: Created a CSV file of the bottom image locations.
The information from the image metadata tags was extracted using the following ExifTool (version 12.30) command:
exiftool -csv -f -DateTimeOriginal -GPSDateStamp -GPSTimeStamp -GPSLatitude -GPSLongitude -n *.JPG > out.csv
Microsoft Excel was used to rename the field names for the filename (PICNAME), original camera time (CAMR_TIME), GPS date (DATE), GPS time (GPSTIME), latitude (LAT), and longitude (LONG); add new fields for the camera (CAMERA), time offset applied to the camera time (TIMEOFFSET), Julian day of collection (JD), year of collection (YEAR), survey ID (FA_ID), sampling device used to collect the image (DEVICE_ID), and survey vessel (VEHICLE_ID); and remove additional fields extracted from the ExifTool command.

Step 8: Created a final shapefile and CSV file of the bottom image locations.
A shapefile was created from the bottom image locations CSV file using the Make XY Event Layer then exporting to a feature (right click, Data, Export Features) in Esri ArcGIS Pro (version 2.0.1). The Spatial Join tool was then run to determine the sampling site number (FIELD_NO) for each bottom image by joining the attributes of a shapefile with the nearest sampling station using the distance within option with a search radius of 200 meters. Unnecessary fields created when running the Spatial Join tool were deleted (i.e., Join_Count and TARGET_FID). The shapefile was reordered using the Sort tool to sort the images in chronological order (JD and GPSTIME sort fields in ascending order). Finally, the shapefile's attribute table was exported in Esri ArcGIS Pro and saved as a CSV file. The ObjectID field was deleted in the CSV file.