Attribute_Accuracy_Report:
The end time of the video drift used to map the bottom video tracklines (field ENDTIME in the shapefile) was calculated using the video start time and duration. This end time may be off by up to two seconds and was not assessed for accuracy by comparing it with the time burned on to the upper right corner of the video's last frame.
All bottom videos were acquired using a SeaViewer 6000 HD Sea-Drop video camera on the mini-SEABOSS. Gaps in sequential clip numbers exist because videos taken in the water column were not processed. The tracklines may self-intersect or self-overlap; at times the ship was moving so slowly that the resolution of the Differential Global Positioning System (DGPS) makes a trackline appear to double back on itself.
This dataset includes bottom video in MP4 format and a trackline shapefile of the location of the ship for the duration of the video during USGS survey 2018-049-FA. 70 stations were occupied within the study area, and bottom video was acquired at 68 of the 70 stations. Poor visiblity and/or recording malfunctions at stations 2018-049-FA-053 and 2018-049-FA-059 resulted in no usable video footage. Stations 2018-049-FA-005, 2018-049-FA-016, 2018-049-FA-063, and 2018-049-FA-068 have two video clips each.
Horizontal_Positional_Accuracy:
Horizontal_Positional_Accuracy_Report:
Sources of horizontal inaccuracy may be due to the video start and end times used to create the shapefile or the navigation data. The end time of the video drift used to map the bottom video tracklines (field ENDTIME in the shapefile) was calculated using the video start time and duration, rather than using the time burned on the upper right corner of the video's last frame. The calculated end time may be off by up to two seconds and accounts for +/- 1 meter of horizontal uncertainty. The R/V Petrel's Differential GPS (DGPS) system supplied navigation for survey 2018-049-FA. The GPS was set to receive fixes at a one-second interval in geographic coordinates (World Geodetic System of 1984 [WGS 84]) however in some cases where navigation may have dropped for a short amount of time, the location was interpolated (see process steps). The recorded position of each image is the position of the GPS antenna on the survey vessel, located on the aft starboard side of the wheelhouse, not the location of the SEABOSS sampler. The antenna was located approximately 3 meters from the deployment point of the sampler. No layback or offset was applied to the recorded position. In addition, the sampler may drift away from the survey vessel when deployed to the sea floor. Based on the various sources of horizontal offsets, a conservative estimate of the horizontal accuracy of the bottom image locations is 5-7 meters.
Source_Information:
Source_Citation:
Citation_Information:
Originator: U.S. Geological Survey
Publication_Date: Unpublished Material
Title: Bottom video and navigation data
Geospatial_Data_Presentation_Form: video and tabular digital data
Type_of_Source_Media: disc
Source_Time_Period_of_Content:
Time_Period_Information:
Range_of_Dates/Times:
Beginning_Date: 20181022
Ending_Date: 20181023
Source_Currentness_Reference:
ground condition of field activity 2018-049-FA: 20181022-20181023
Source_Citation_Abbreviation: Bottom video and raw navigation files
Source_Contribution:
Bottom imagery was acquired using the mini-SEABOSS. The observations from still and video cameras and the sediment data are used to explore the nature of the sea floor and, in conjunction with high-resolution geophysical data, to make interpretive maps of sedimentary environments and validate acoustic remote sensing data. This configuration of the mini-SEABOSS incorporates a downward-looking SeaViewer HD video camera with a topside feed, two GoPro HERO4 Black cameras recording still images (one was attached to the SEABOSS frame another was extended on a removable pole that was forward of the SEABOSS approximately 1 meter in hopes of getting a clearer, unobstructed view of the seabed), a modified Van Veen sediment grab sampler, and lights to illuminate the seabed for video and photographs. The elements of this particular SEABOSS system are held within a stainless-steel frame that measures 0.9 x 0.9 x 1.25 meters. The frame has two stabilizer fins that orient the system as it drifts over the seabed. Two red lasers were set 20 centimeters apart (both as they are mounted on the SEABOSS frame and as seen in photographs and video on the seabed) for scale measurements. The red laser dots can usually be seen in the imagery depending on the bottom type and distance to the sea floor. The R/V Petrel occupied one of the target stations and the SEABOSS was deployed off the vessel's A-frame on the stern of the ship. The winch operator lowered the sampler until the sea floor was observed in the topside live video feed. The vessel and sampler then drifted with wind and current for up to a few minutes to ensure a decent image with a clear view of the sea floor was acquired. Usually at the end of a short drift, the winch operator lowered the Van Veen sampler until it rested on the sea floor. When the system was raised, the Van Veen sampler closed and collected a sample as it was lifted off the sea floor. The sampler was recovered to the deck of the survey vessel where a subsample was taken for analysis at the sediment laboratory at the USGS Woods Hole Coastal and Marine Science Center. The GoPro camera time were set to UTC; calibration photographs with the navigation system indicate that the camera time were off by an average of 5 seconds from the GPS time, so the time offsets were corrected during the geotagging process. During some of the survey, the seabed turbidity made it such that no usable images were able to be acquired. In these cases, brief glimpses of the sea floor may be visible in the coincident video files. Bottom video was recorded from the downward-looking camera directly to hard drives using an Odyssey7 video recorder. The image dimensions of the GoPro photos are 4,000 x 3,000 pixels. The imaged area is most often within 0.5 to 1.25 meters from left to right. DGPS navigation from the R/V Petrel's Hemisphere VS330 GPS receiver was logged to the ship's HYPACK computer (HYPACK version 2017a) and, as a backup, through ArcGIS using the ArcMap GPS extension. The main source of navigation data was the ship's HYPACK files.
Process_Step:
Process_Description:
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 R/V Rafael occupied one of the target stations, the mini-SEABOSS sampler was deployed, and then the vessel and sampler drifted with wind and current for up to a few minutes to ensure a decent video with a clear view of the sea floor. Bottom video was recorded from the downward-looking SeaViewer video camera directly on to SSD media using an Odyssey7 video recorder. This process step and all subsequent steps were performed by the same person unless otherwise noted.
Process_Date: 20181023
Source_Produced_Citation_Abbreviation: Original bottom video
Process_Contact:
Contact_Information:
Contact_Person_Primary:
Contact_Person: Seth Ackerman
Contact_Organization: U.S. Geological Survey
Contact_Position: Geologist
Contact_Address:
Address_Type: mailing and physical address
Address: 384 Woods Hole Rd.
City: Woods Hole
State_or_Province: MA
Postal_Code: 02543-1598
Country: USA
Contact_Voice_Telephone: 508-548-8700 x2315
Contact_Facsimile_Telephone: 508-457-2310
Contact_Electronic_Mail_Address: sackerman@usgs.gov
Process_Step:
Process_Description:
The original video files were copied from the Odyssey7 SSD to the processing computer. A shell script (TCBURN_2018-049_sda2txt_NEW.csh) was run, using FFMPEG and FFPROBE to join the video clips for each station (the Odyssey7 splits clips into less than 4GB segments), burn the date and time in UTC on to the upper right corner of the video, and transcode the video from MOV to MP4 format. The script also created a text file with the date, start time, and duration of each video recording. The videos were renamed to include the sampling site ID (which includes the field activity identifier), camera, and date and start time in the ISO 8601 standard in the filename.
Source_Used_Citation_Abbreviation: Original bottom video
Process_Date: 201902
Source_Produced_Citation_Abbreviation: Final bottom video
Source_Produced_Citation_Abbreviation: Start times/durations text file
Process_Step:
Process_Description:
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. 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. Part 2 of a Python Jupyter Notebook (Hypack_NJ2018-Feb2020.ipynb) then reads back in these RAW files and outputs parsed navigation data files called Oct22_parsed.csv and Oct23_parsed.csv.
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, so the Oct23_parsed.csv file was renamed Oct23_parsed_v2_Hypack_gap.csv. To account for the missing time period, backup GPS data logged in the ArcMap were extracted from the shapefile, exported to a csv file (Oct23_parsed_v2_ArcMap_gapfill.csv), reformatted to match the parsed HYPACK navigation data file, and combined with that file to create a new file for the entire day (Oct23_parsed_v3_filled.csv).
The resulting navigation files for each day (Oct22_parsed.csv and Oct23_parsed_v3_filled.csv) were then each run through a Python Jupyter Notebook (Interp_NAV_Feb2020_forNJ2018-049.ipynb) that performed an interpolation routine that filled small gaps in the navigation, usually on the order of 10 to 30 second dropouts.
The two interpolated navigation files were concatenated into the file 2018-049-FA_AllNav_interpolated_FINAL.csv
Source_Used_Citation_Abbreviation: Raw HYPACK navigation files
Source_Used_Citation_Abbreviation: Esri point shapefiles
Process_Date: 20200212
Source_Produced_Citation_Abbreviation: Processed interpolated navigation file
Process_Step:
Process_Description:
A Jupyter Notebook Python script (Video_trackline_prep_WORKING_v2.ipynb) was run to create a shapefile of the bottom video trackline points by extracting the navigation fixes for each video drift using information from the start times/durations text file. The script reads the video start time and duration from the text file, calculates the video end time, extracts the navigation points that fall within those start and end times, and exports the navigation fixes to a CSV file (Vidpoints_2018-049-FA_All.csv). The script also creates an Esri Point Shapefile (Vidpoints_2018-049-FA_All.shp) that can be used to create a trackline for each video location.
Source_Used_Citation_Abbreviation: Processed navigation file
Source_Used_Citation_Abbreviation: Start times/durations text file
Process_Date: 20200403
Source_Produced_Citation_Abbreviation: Bottom video track point CSV file
Source_Produced_Citation_Abbreviation: Bottom video track point shapefile
Process_Step:
Process_Description:
The point shapefile created in the previous step was converted to a polyline shapefile in QGIS (version 3.10) using the Points to Path tool (Input point layer: Vidpoints_2018-049-FA_All.shp; Order field: jd_time; Group field: vidname; Date format: blank; Paths: 2018-049-FA_VideoLines.shp). Video trackline lengths were calculated using the QGIS tool Add Geometry Attributes (using the project CRS to achieve trackline length in meters). The attribute table field names were updated using the Layer Properties dialog and new fields for date of collection (DATE), camera used (CAMERA), survey ID (FA_ID), sampling device used to collect the video (DEVICE_ID), and survey vessel (VEHICLE_ID). The QGIS tool Refactor was used to reorder the fields and set the precision for the new length field.
Source_Used_Citation_Abbreviation: Bottom video track point shapefile
Process_Date: 20200403
Source_Produced_Citation_Abbreviation: Bottom video tracklines shapefile
