ROV dives tracked using the USBL navigation system were conducted during daytime operations (generally between approximately 10:00 and 23:00 UTC) on May 8-11 (JD128 - JD130), 2017. Navigation for four dives, numbered 3-6 are included in the shapefiles '2017-001-FA_ROVUSBLNavPoints.shp' and '2017-001-FA_ROVUSBLTracklines'.
USBL navigation was not available during the first offshore dive of the field activity at Washington Canyon on May 4, 2017 (JD124) due to inoperability of the USBL system. Additionally, USBL navigation collected during the second dive within the Delaware River estuary on May 7, 2017 (JD127) for system troubleshooting is not included in the data release.
Horizontal_Positional_Accuracy:
Horizontal_Positional_Accuracy_Report:
Ship navigation was supplied to the Applied Acoustics EasyTrack Nexus 2 USBL system from the ships POS/MV inertial navigation system with intermittent success through May 4 (JD124) of 2017-001-FA, but for the remainder of the cruise ship navigation was supplied by a Hemisphere GPS receiver with the GPS antenna mounted on the aft 01 deck handrail approximately 3.4 meters aft and 4 meters to port of the USBL transceiver. The USBL acoustic transceiver was mounted in the rear slot of the retractable keel of the R/V Hugh R. Sharp, which is located approximately amidships on the center line of the vessel, and two 1100 series remote beacons mounted on the ROV main vehicle and controller pod, respectively. The USBL system calculated the bearing and slant range between the transceiver and remote beacons, as well as depths and positions of the beacons relative to the ship, corrected for pitch, roll, and installation offsets. HYPACK calculated the final positions of the ROV vehicle by applying the computed relative offsets to ship positions at corresponding UTC times. GPS horizontal positional accuracy is assumed to be within 3 m and accuracy of the positions and bearings can be up to 0.12 percent of the slant range and 0.01 degrees, respectively. After filtering the calculated positions (see description in the processing steps below) to remove scatter of up to a kilometer outside of the dive area footprints, the accuracy of the remaining positions are estimated to be within 50 meters. Factors possibly contributing to uncertainties in the calculated positions include calibration of the system in an environment considerably different from the survey area (estuary versus offshore), inadequate characterization of water column sound speeds, or acoustic interference from other water column noise sources (multipath interference, bubble wash beneath the ships keel, interference with the concurrently operated split-beam sonar).
Source_Information:
Source_Citation:
Citation_Information:
Originator: U.S. Geological Survey
Publication_Date: unpublished material
Title: HYPACK raw navigation
Geospatial_Data_Presentation_Form: digital data
Type_of_Source_Media: disc
Source_Time_Period_of_Content:
Time_Period_Information:
Range_of_Dates/Times:
Beginning_Date: 20170508
Ending_Date: 20170511
Source_Currentness_Reference: ground condition
Source_Citation_Abbreviation: SEG-Y SB-512i data
Source_Contribution:
The Applied Acoustics EasyTrack Nexus 2 USBL system was used to provide navigation for ROV Global Explorer dives during field activity 2017-001-FA. The system consisted of a hemispherical acoustic transceiver mounted in the rear slot of the retractable keel of the R/V Hugh R. Sharp, which is located approximately amidships on the center line of the vessel, and two 1100 series remote beacons mounted on the ROV main vehicle and controller pod, respectively. Ship navigation was initially supplied to the USBL system from the ships POS/MV inertial navigation system with intermittent success through May 4 (JD124) of 2017-001-FA, but for the remainder of the cruise ship navigation was supplied by a Hemisphere Differential GPS (DGPS) receiver with the DGPS antenna mounted on the aft 01 deck handrail approximately 3.4 meters aft and 4 meters to port of the USBL transceiver. While surveying, the retractable keel was lowered to 1-meter below the hull, resulting in a draft of 5.06 meters below the waterline. The EasyTrack Nexus 2 (version 2.0.2.1) software controlled the USBL system acquisition, logged the raw data stream (*.epb format), and output calculated bearing, slant range, depth, and position of the ROV vehicle relative to the ship (corrected for pitch, roll, and installation offsets) as an ORE Trackpoint 2EC string over a serial connection. HYPACK (version 2017, 17.1.3.0) survey software was used to monitor the serial connection using its 'Trackp.dll' driver, calculate the position of the ROV in WGS84, UTM 18 North, meters, and log the string transmitted from USBL system and the calculated position as messages in the HYPACK raw files. A network protocol time server was used to synchronize both the USBL and HYPACK acquisition computers to GPS time. Calibration procedures for the USBL system were conducted in the Delaware River estuary prior to conducting dives 3 - 5. Sound velocity profiles calculated from XBT casts were provided to the EasyTrack Nexus 2 software for use in range calculations.
Process_Step:
Process_Description:
PROCESS STEP 1:
Unix shell programs were used to extract a subset of USBL position data and group the data by dive as follows:
1)'grep' was used to extract all USBL ROV position messages from HYPACK raw files; the messages were piped to 'awk', which conditionally filtered the input to create a subset containing every fifth input message, converted the HYPACK time stamp (in seconds after midnight) to a fractional day value (divided by 86400 seconds/day), and printed the HYPACK time stamp, fractional day value, easting, and northing values to temporary output ASCII text files.
2) 'cat' was used to concatenate all temporary text files for each dive into a single file per dive.
Process steps 1 and 2 were conducted by Carolyn Ruppel.
Process_Date: 201705
Process_Contact:
Contact_Information:
Contact_Organization_Primary:
Contact_Organization: U.S. Geological Survey
Contact_Person: Carolyn D. Ruppel
Contact_Position: Geophysicist
Contact_Address:
Address_Type: mailing and physical address
Address: 384 Woods Hole Rd.
City: Woods Hole
State_or_Province: MA
Postal_Code: 02543-1598
Contact_Voice_Telephone: (508) 548-8700 x2339
Contact_Facsimile_Telephone: (508) 457-2310
Contact_Electronic_Mail_Address: cruppel@usgs.gov
Process_Step:
Process_Description:
PROCESS STEP 2:
Microsoft Excel 2019, ArcMap (version 10.5), and XTools Pro (version 19) were used to edit and create point and trackline shapefiles from the individual dive ASCII text files:
1) The ASCII text files for each dive were opened in Excel and the fractional day column was converted to hh:mm:ss time format in the process. Each file was saved to the comma separated values (CSV) format with headers for each column.
2) Navigation data for each dive were imported from the CSV files into ArcMap (Add XY data) specifying WGS84, UTM 18 North as the coordinate system and saved to new point shapefiles.
3) XTools Pro polylines from points was used to create a trackline shapefile from each new point shapefile using FID as the sort order field.
4) Point and polyline shapefile pairs were examined together to evaluate the data for obviously erroneous navigation points (easily identified by impossibly large polyline deviations). Points identified as outliers were eliminated from the point shapefiles and after saving changes, the polylines from points operation was repeated to create a new dive trackline from the edited point data. In some instances this was an iterative process.
5) The ArcMap data frame was reprojected from UTM 18N to WGS84 geographic coordinate system, then field names for longitude and latitude were added to the attribute tables of the point shapefiles and each were populated using calculate geometry in WGS84 geographic coordinates. Each point and polyline shapefile was exported to new geographic files using the coordinates of the data frame.
Process_Date: 201705
Process_Step:
Process_Description:
PROCESS STEP 3:
XTools Pro and ArcMap (10.7.1) were used to modify the attribute tables of the geographic point and polyline shapefiles and merge them into one file each containing data for all the dives.
1) XTools Pro modify table was used to delete (HYPACK time stamp), define and populate by expression (DiveOp, Year, JD_UTC, SurveyID, VehicleID, RovID, and DeviceID), and reorder fields in the individual dive point shapefile attribute tables. The resulting fields are "East, North, Lon, Lat, DiveOp, Year, JD_UTC, SurveyID, VehicleID, RovID, and DeviceID.
2) ArcMap Merge was used to combine the point (with modified tables) and polyline shapefiles from each dive into a single file for each feature type; '2017-001-FA_ROVUSBLNavPoints.shp' and '2017-001-FA_ROVUSBLTracklines.shp', respectively.
3) XTools Pro modify table was used to define the fields "DiveOp, Year, JDUTC_init, JDUTC_end, SurveyID, VehicleID, RovID, and DeviceID" in the attribute table of '2017-001-FA_ROVUSBLTracklines.shp'. The field s "Year, SurveyID, VehicleID, RovID, and DeviceID" were populated by expression using the field calculator, and "DiveOp, JDUTC_init, JDUTC_end" were populated by hand with values copied from the attribute tables of the individual dive point shapefiles.
4) XTools Pro calculate geometry was used to create the field "Length_km" in the attribute table of '2017-001-FA_ROVUSBLTracklines.shp' and populate it with the lengths of each polyline feature in the file calculated in WGS84, UTM 18 North, kilometers.
Process_Date: 202001
Process_Contact:
Contact_Information:
Contact_Organization_Primary:
Contact_Organization: U.S. Geological Survey
Contact_Person: Wayne E. Baldwin
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
Contact_Voice_Telephone: (508) 548-8700 x2226
Contact_Facsimile_Telephone: (508) 457-2310
Contact_Electronic_Mail_Address: wbaldwin@usgs.gov
Process_Step:
Process_Description:
Added keywords section with USGS persistent identifier as theme keyword.
Process_Date: 20200806
Process_Contact:
Contact_Information:
Contact_Organization_Primary:
Contact_Organization: U.S. Geological Survey
Contact_Person: VeeAnn A. Cross
Contact_Position: Marine Geologist
Contact_Address:
Address_Type: Mailing and Physical
Address: 384 Woods Hole Road
City: Woods Hole
State_or_Province: MA
Postal_Code: 02543-1598
Contact_Voice_Telephone: 508-548-8700 x2251
Contact_Facsimile_Telephone: 508-457-2310
Contact_Electronic_Mail_Address: vatnipp@usgs.gov
