Photographs and locations of bottom still imagery collected in Little Egg Inlet and offshore the southern end of Long Beach Island, NJ, during USGS Field Activity 2018-049-FA (JPEG images, point shapefile, and CSV file)

A total of 70 sites were occupied aboard the R/V Petrel with the mini-SEABOSS (Blackwood and Parolski, 2001) in October 2018 during USGS survey 2018-049-FA. See the source contribution section of this metadata file for additional system configuration details. The set of photographs collected by the SEABOSS was culled to remove images on deck, in the water column, blurry images of the seabed. For some sites that had many usable images, although of the same or similar seabed, only a handful of these good images were kept for publication in this data release to provide a representative view of the sea floor. This process step and all subsequent steps were performed by the same person unless otherwise noted.

DGPS navigation from a Hemisphere VS330 receiver was logged with the ship's HYPACK computer and, as a backup, through ArcGIS using the ArcMap GPS extension. The GPS was set to receive fixes at a one-second interval in geographic coordinates (WGS 84). Dates and times were recorded in Coordinated Universal Time (UTC). The primary navigation log files (from HYPACK) were saved for each Julian day in HYPACK RAW format. The backup navigation logged in ArcGIS was saved as Esri point shapefiles.

Navigation dropouts required the images to be processed in 3 sets based on the available navigation data: HYPACK-recorded navigation was used for 155 images, though 10 of these images were captured during small HYPACK navigation dropouts (each less than 20-40 seconds) and required interpolation across the small gaps using Exiftool (version 11.11); 17 images had to be processed with the ArcMap-recorded navigation due to a 1-hour HYPACK logging gap on Oct 23. Note: Navigation for both streams were recorded from the same antenna and receiver on the ship.
Part 1 of a Python Jupyter Notebook (Hypack_NJ2018-Feb2020.ipynb) was run on the log files to parse for the GPRMC navigation string and create ASCII Comma Separated Values (CSV) text files (each one with "_out.txt" appended to the original filename). These output files were concatenated together for each survey day separately creating the files Oct22_ALLNav_v2_Hypack.RAW and Oct23_ALLNav_v2_Hypack.RAW. These files were then edited in the VI editor to remove the HYPACK formatting at the start of each line (":%s/^.\{16}//g"), resulting in a standard NMEA GPRMC string, which was saved as files Oct22_ALLNav_v2_GPRMC.NMEA and Oct23_ALLNav_v2_GPRMC.NMEA.
An extended dropout in HYPACK navigation recording occurred on October 23 between 15:52:48 and 16:51:03 UTC during deployments at sampling sites 2018-049-FA-062 and 2018-049-FA-063. Backup GPS data logged in Esri ArcMap were used to fill the approximately 1-hour gap (17 photos). This navigation was converted to a GPS track log file format (GPX) that is supported by ExifTool. The ArcMap-logged navigation was exported from ArcGIS (version 10.3) to a CSV text file, which was then converted to a GPX file (20200213065707-32034-data.gpx) using GPS Visualizer (http://www.gpsvisualizer.com/convert_input?convert_format=gpx, accessed February 13, 2020.
Several smaller navigation dropouts affected both recording systems but an interpolation capability in the ExifTool program (described below) can account for these small gaps.

The original JPEG images alone do not represent spatial data, however, they can be geolocated by linking the time the image was taken, which was recorded in the JPEG files' Exchangeable image file format (Exif) headers, to the corresponding time in the navigation logs. Camera time drift and the precision with which the camera time can be set often result in a time offset. The camera time of the GoPro HERO4 Black was set to UTC at the start of the survey. Calibration photographs with the navigation system indicate that the camera time was approximately 5 seconds ahead of the GPS time for the duration of the survey. This time offset was corrected by subtracting five seconds from the camera time for all photos during the geotagging process.
To geotag the images, the following commands were used with ExifTool (version 11.11) to populate the GPS tags (GPSLatitudeRef, GPSLatitude, GPSLongitudeRef, GPSLongitude, GPSTimeStamp, and GSPDateStamp) in the Exif header of each JPEG image:
145 images coincident with the HYPACK-recorded navigation:exiftool -api GeoMaxIntSecs=2 -api GeoMaxExtSecs=0 -P -m -geotag ./ALL_NMEA.NMEA -geosync=-5 '-geotime<${DateTimeOriginal}' ./pics_wHypackNav/pics/*.JPG
10 images among the small gaps from the HYPACK-recorded navigation:exiftool -api GeoMaxIntSecs=40 -api GeoMaxExtSecs=0 -P -m -geotag ./ALL_NMEA.NMEA -geosync=-5 '-geotime<${DateTimeOriginal}' ./pics_wInterpNav/pics/*.JPG
17 images during 1-hour gap in HYPACK-recorded navigation but coincident with the ArcMap-recorded navigation:exiftool -api GeoMaxIntSecs=2 -api GeoMaxExtSecs=0 -P -m -geotag ./20200213065707-32034-data.gpx -geosync=-5 '-geotime<${DateTimeOriginal}' ./pics_wArcGISNav/pics/*.JPG
The descriptions of the ExifTool arguments are as follows:
-api GeoMaxIntSecs=2 or -api GeoMaxIntSecs=40: an option configured to set the maximum interpolation time for geotagging. Geotagging is treated as an extrapolation if the Geotime value (which is equal to DateTimeOriginal in this case) lies between two fixes in the same track that are separated by a number of seconds greater than this (provided it is within GeoMaxExtSecs, otherwise geotagging fails). Otherwise, the coordinates are calculated as a linear interpolation between the nearest fixes on either side of the Geotime value.
-api GeoMaxExtSecs=0: an option configured to set the maximum extrapolation time to zero seconds for geotagging. Geotagging fails if the Geotime value (which is equal to DateTimeOriginal in this case) lies outside a GPS track by a number of seconds greater than this or the maximum interpolation time. Otherwise, the coordinates of the matching fix are taken (if the Geotime matches a time in the GPS track log file) or the coordinates are calculated as a linear interpolation between the nearest fixes on either side of the Geotime value.
-P: an option to preserve the FileModifyDate.
-m: an option used for the GoPro photos to ignore 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 the GoPro images: Warning: [minor] Unrecognized MakerNotes; Warning: [minor] Maker notes could not be parsed.
-geotag: a tag used to add GPS tags to images based on data from a GPS track log file../ALL_NMEA.NMEA or ./20200213065707-32034-data.gpx: the GPS track log files used to geotag in NMEA and GPX file formats, respectively, in the current directory the script is run from.
--geosync=-5: a tag used when the image timestamps are not properly synchronized with GPS time. The value written to Geosync may take a number of different forms, but this format is the time difference in seconds that is added to Geotime before interpolating the GPS position in the track log. A leading "+" or "-" is added for positive or negative differences (negative if the camera clock was ahead of GPS time). A time offset was applied to all the GoPro photos from survey 2019-049-FA.'
-geotime<${DateTimeOriginal}+00:00': an argument added to geotag images for which the camera clock was set to UTC (+00:00) using the time from DateTimeOriginal
./pics_wHypackNav/pics/*.JPG, ./pics_wInterpNav/pics/*.JPG, ./pics_wArcGISNav/pics/*.JPG: directory and wildcard to specific the images to be geotagged.
The above definitions are from https://www.sno.phy.queensu.ca/~phil/exiftool/geotag.html and https://www.sno.phy.queensu.ca/~phil/exiftool/faq.html.
Note: the computer clock on the processing computer was changed to UTC time zone prior to running these scripts to ensure that the photo and navigation times matched correctly.

All of the geotagged images were moved to a single directory and the following command was run using ExifTool (version 11.11) to rename the photos using a schema that adds field activity number, device and camera identifier, and the UTC time the image was captured to the filename:
exiftool -d 2018049FA_SEABOSSg45_%Y%m%dT%H%M%SZ_%%f.%%e "-filename<GPSdatetime" *.JPG
The descriptions of the ExifTool arguments are as follows:
-d: sets the format for date and time fields
2018049FA_SEABOSSg45_%Y%m%dT%H%M%SZ_%%f.%%e: this is the output filename format where "2018049FA" indicates the field activity 2018-049-FA; "SEABOSSg45" indicates the platform was the SEABOSS with the GoPro Hero 4 (WHCMSC camera #5); "%Y%m%dT%H%M%SZ" indicates that ExifTool should format the date and time parsed from the specified tag with "%Y" = 4-digit year, %m = month, %d = day, the letter "T" delineating the beginning of the time part, %H%M%S as time in 24-hour format hour minute seconds, then the letter "Z" indicating Zulu/UTC timezone."
-filename<GPSdatetime": this indicates that the GPSdatetime tag will be used for the new filenames*.JPG: indicates the set of photos to process with this script

The following command was then used with ExifTool (version 11.11) to incorporate additional survey information into the appropriate tags in the Exif and other headers of each JPEG image. Information is duplicated in some tags because various software packages access different tags. Please note that depending on the software used to view the header tags, only a subset of these tags may be extracted.
exiftool -P -Artist="Seth D. Ackerman" -comment="Photo from down-looking camera on the USGS mini-SEABOSS deployed from the R/V Petrel during survey 2018-049-FA (https://cmgds.marine.usgs.gov/fan_info.php?fan=2018-049-FA)." -sep ";" -keywords="Little Egg Inlet; Beach Haven; Long Beach Island; Hogate; Forsythe Wildlife Refuge; New Jersey; 2018-049-FA; SEABOSS; sea floor; USGS" -Caption="Photograph of the sea floor in off Long Beach Island, New Jersey from USGS field activity 2018-049-FA" -Caption-Abstract="Photograph of the sea floor in off Long Beach Island, New Jersey from USGS field activity 2018-049-FA" -ImageDescription="Photograph of the sea floor in off Long Beach Island, New Jersey from USGS field activity 2018-049-FA" -Credit="U.S. Geological Survey" -Contact="WHSC_data_contact@usgs.gov" -Copyright="Public Domain - please credit U.S. Geological Survey" -CopyrightNotice="Public Domain - please credit U.S. Geological Survey" *.JPG
The following tags were populated in the JPEG image headers:JPEG tag and the information used to populate this tag:
Comment: Photo from down-looking camera on the USGS mini-SEABOSS deployed from the R/V Petrel during survey 2018-049-FA (https://cmgds.marine.usgs.gov/fan_info.php?fan=2018-049-FA)
Exif tags and the information used to populate these tags:
ImageDescription: Photograph of the sea floor in off Long Beach Island, New Jersey from USGS field activity 2018-049-FA
Artist: Seth D. AckermanCopyright: Public Domain - please credit U.S. Geological Survey
International Press Telecommunications Council (IPTC) tags and the information used to populate these tags:
Credit: U.S. Geological Survey
Contact: WHSC_data_contact@usgs.gov
Keywords: Little Egg Inlet; Beach Haven; Long Beach Island; Hogate; Forsythe Wildlife Refuge; New Jersey; 2018-049-FA; SEABOSS; sea floor; USGS
CopyrightNotice: Public Domain - please credit U.S. Geological Survey
Caption-Abstract: Photograph of the sea floor in off Long Beach Island, New Jersey from USGS field activity 2018-049-FA
Extensible Metadata Platform (XMP) tag and the information used to populate this tag:
Caption: Photograph of the sea floor in off Long Beach Island, New Jersey from USGS field activity 2018-049-FA
To extract the information from the image headers using ExifTool, the following command can be used (tested with ExifTool version 11.11):
exiftool -csv -f -filename -GPSTimeStamp -GPSDateStamp -GPSLongitude -GPSLatitude -n -Artist -Credit -comment -keywords -Caption -Copyright -CopyrightNotice -Caption-Abstract -ImageDescription *.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.

The information from the image headers was extracted using the following ExifTool (version 11.11) commands:
exiftool -csv -GPSDateTime -DateTimeOriginal -GPSLatitude -GPSLongitude -n *.JPG > 2018049FA_photos_temp.csv
Then Microsoft Excel for Mac (version 16.35) was used to: rename the field names for the filename (PICNAME), GPS time (GPS_DTUTC), original camera time (CAM_DTUTC), longitude (LONG) and latitude (LAT); add new fields including an attribute for the camera (CAMERA), time offset applied to the camera time for matching GPS time (TIMEOFFSET), survey ID (FA_ID), sampling device used to collect the imagery (DEVICE_ID), and survey vessel (VEHICLE_ID). The table was exported to a CSV file called 2018049FA_photos_temp2.csv.

A shapefile was created by importing the bottom image locations CSV file into QGIS (version 3.10). In QGIS, the NNJoin plugin (version 3.1.3) was used to perform a spatial join between the photo locations layer and the sediment lab analyses data. All sediment lab data except for the field identifying the nearest sediment sample location (SMPL_SITE) were then removed from the joined dataset. The attribute table was manually edited to account for the photos acquired at sample sites 2018-049-FA-026 and 2018-049-FA-047 where no sediment sample was collected, and the automated spatial join recorded the next nearest sample site. The attribute table was reordered and the position (lat/long) precision was set to 6 decimal places using the Refactor Fields tool in the QGIS Processing Toolbox. The field names were updated as needed using the Layer Properties dialog. The final photo locations shapefile was saved and a CSV file containing the same attributes as the shapefile was exported.