Chandeleurs_2013_50_NAD83_NAVD88_GEOID09_DEM.tif: 50-Meter Digital Elevation Model (DEM) of Coastal Bathymetry Collected in 2013 from the Chandeleur Islands, Louisiana (U.S. Geological Survey (USGS) Field Activity Numbers (FAN) 13BIM02, 13BIM03, 13BIM04, 13BIM07, and 13BIM08.)

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Frequently anticipated questions:


What does this data set describe?

Title:
Chandeleurs_2013_50_NAD83_NAVD88_GEOID09_DEM.tif: 50-Meter Digital Elevation Model (DEM) of Coastal Bathymetry Collected in 2013 from the Chandeleur Islands, Louisiana (U.S. Geological Survey (USGS) Field Activity Numbers (FAN) 13BIM02, 13BIM03, 13BIM04, 13BIM07, and 13BIM08.)
Abstract:
As part of the Barrier Island Evolution Research Project, scientists from the U.S. Geological Survey (USGS) St. Petersburg Coastal and Marine Science Center (SPCMSC) conducted nearshore geophysical surveys around the northern Chandeleur Islands, Louisiana, in July and August of 2013. The objective of the study is to better understand barrier-island geomorphic evolution, particularly storm-related depositional and erosional processes that shape the islands over annual to interannual timescales (1‒5 years). Collecting geophysical data will allow us to identify relationships between the geologic history of the island and its present day morphology and sediment distribution. This mapping effort was the third in a series of three planned surveys in this area. High resolution geophysical data collected in each of three consecutive years along this rapidly changing barrier island system will provide a unique time-series dataset that will significantly further the analyses and geomorphological interpretations of this and other coastal systems, improving our understanding of coastal response and evolution over short time scales (1‒5 years). This data series includes the geophysical data that were collected during two cruises (USGS Field Activity Numbers (FAN) 13BIM02, 13BIM03, and 13BIM04, in July 2013; and FANs 13BIM07 and 13BIM08 in August 2013) aboard the R/V Sallenger, the R/V Jabba Jaw, and the R/V Shark along the northern portion of the Chandeleur Islands, Breton National Wildlife Refuge, Louisiana. Primary data were acquired with the following equipment: (1) a Systems Engineering and Assessment, Ltd., SWATHplus interferometric sonar (468 kilohertz [kHz]), (2) an EdgeTech 424 (424 kHz) chirp sub-bottom profiling system, and (3) two Teledyne Odom Hydrographic Systems, Incorporated, Echotrach CV100 single beam echosounders.
This data series report serves as an archive of processed interferometric swath and single-beam bathymetry data. Geographic information system data products include an interpolated digital elevation model, trackline maps, and point data files. Additional files include error analysis maps, Field Activity Collection System logs, and formal Federal Geographic Data Committee metadata.
Note: These data are scientific in nature and are not to be used for navigation purposes. Any use of trade names is for descriptive purposes only and does not imply endorsement by the U.S. Government.
Supplemental_Information:
Both the single-beam and interferometric swath surveys were acquired and processed to a geodetic reference ellipsoid.
The interferometric swath bathymetry navigation data was acquired with Marinestar High Precision (HP) Differential Geographic Positioning System (DGPS), which used the ITRF2005 datum.
The single-beam bathymetry data was acquired using real-time kinematics (RTK) for 13BIM03 and 13BIM04 in July. The single-beam bathymetry data for 13BIM08 in August was post-processed to obtain DGPS navigation. Both single-beam surveys were referenced to WGS84 (G1150)/ITRF00.
Both SBB and IFB datasets were transformed horizontally to NAD83 and then vertically to NAVD88 using GEOID09 (NOAA NGS VDatum software version 3.3, (http://vdatum.noaa.gov/). The final x,y,z position data from each survey were merged to generate a DEM with a resolution of 50-meter (m) cell size.
  1. How might this data set be cited?
    U.S. Geological Survey, 2017, Chandeleurs_2013_50_NAD83_NAVD88_GEOID09_DEM.tif: 50-Meter Digital Elevation Model (DEM) of Coastal Bathymetry Collected in 2013 from the Chandeleur Islands, Louisiana (U.S. Geological Survey (USGS) Field Activity Numbers (FAN) 13BIM02, 13BIM03, 13BIM04, 13BIM07, and 13BIM08.):.

    Online Links:

    This is part of the following larger work.

    DeWitt, Nancy T., Miselis, Jennifer L., Fredericks, Jake J., Bernier, Julie C., Reynolds, B.J., Kelso, Kyle W., Thompson, Dave M., Flocks, James G., and Wiese, Dana S., 2017, Coastal Bathymetry Data Collected in 2013 from the Chandeleur Islands, Louisiana: U.S. Geological Survey Data Series 1032, U.S. Geological Survey, St. Petersburg, FL.

    Online Links:

  2. What geographic area does the data set cover?
    West_Bounding_Coordinate: -88.916525
    East_Bounding_Coordinate: -88.794837
    North_Bounding_Coordinate: 30.097294
    South_Bounding_Coordinate: 29.933714
  3. What does it look like?
  4. Does the data set describe conditions during a particular time period?
    Beginning_Date: 05-Jul-2013
    Ending_Date: 01-Sep-2013
    Currentness_Reference:
    ground condition
  5. What is the general form of this data set?
    Geospatial_Data_Presentation_Form: raster digital data
  6. How does the data set represent geographic features?
    1. How are geographic features stored in the data set?
      This is a Raster data set. It contains the following raster data types:
      • Dimensions 359 x 229 x 1, type Grid Cell
    2. What coordinate system is used to represent geographic features?
      Grid_Coordinate_System_Name: Universal Transverse Mercator
      Universal_Transverse_Mercator:
      UTM_Zone_Number: 16
      Transverse_Mercator:
      Scale_Factor_at_Central_Meridian: 0.9996
      Longitude_of_Central_Meridian: -87.0
      Latitude_of_Projection_Origin: 0.0
      False_Easting: 500000.0
      False_Northing: 0.0
      Planar coordinates are encoded using row and column
      Abscissae (x-coordinates) are specified to the nearest 50
      Ordinates (y-coordinates) are specified to the nearest 50
      Planar coordinates are specified in meter
      The horizontal datum used is North American Datum of 1983 (NAD83).
      The ellipsoid used is GRS 1980.
      The semi-major axis of the ellipsoid used is 6378137.0.
      The flattening of the ellipsoid used is 1/298.257222101.
      Vertical_Coordinate_System_Definition:
      Depth_System_Definition:
      Depth_Datum_Name: North American Vertical Datum 88 (NAVD88)
      Depth_Resolution: 0.1
      Depth_Distance_Units: meter
      Depth_Encoding_Method: Implicit coordinate
  7. How does the data set describe geographic features?

Who produced the data set?

  1. Who are the originators of the data set? (may include formal authors, digital compilers, and editors)
    • U.S. Geological Survey
  2. Who also contributed to the data set?
    U.S. Geological Survey, Coastal and Marine Geology Program, St. Petersburg Coastal and Marine Science Center
  3. To whom should users address questions about the data?
    U.S. Geological Survey
    Attn: Nancy T. DeWitt
    Geologist
    600 4th Street South
    St. Petersburg, FL
    USA

    (727) 502-8000 (voice)
    ndewitt@usgs.gov

Why was the data set created?

This 50-m cell size DEM is an interpretive product that was derived from the processed single-beam bathymetry (SBB) and interferometric swath bathymetry (IFB) data collected in July and August of 2013 around the northern Chandeleur Islands, Louisiana.

How was the data set created?

  1. From what previous works were the data drawn?
  2. How were the data generated, processed, and modified?
    Date: 2013 (process 1 of 8)
    GPS Acquisition: A GPS base station was erected at a temporarily installed USGS benchmark (TMRK) located on the sound side of the Chandeleur Islands. A second base station (BRM2) was erected on the furthest northern island providing differential GPS coverage for the survey area within a 15 km radius of either benchmark. GPS receivers recorded the 12-channel full-carrier-phase positioning signals (L1/L2) from satellites via the Thales choke-ring antenna at the base stations. This GPS instrument combination was duplicated on the single-beam survey vessel (rover).
    The SBB data was acquired using RTK for 13BIM03 and 13BIM04 in July. Both base stations were equipped with a Magellan ProFlex500 GPS receiver, a Thales choke ring antenna, a Pacific Crest ADLP-1 390-430 megahertz (MHz) radio, and a Pacific Crest 5 decibel (dB) high power radio whip antenna. The radio whip antennas were placed onto 10-m collapsible masts providing line of site transmission to the vessels (rovers). The GPS and radio components were duplicated on each vessel. The base stations were set to record internally at a rate greater than or equal to the recording rate of the rovers, in this case 5 Hz. The known coordinates of each base station were entered into the GPS receiver and the RTK corrections were broadcast to the roving GPS receivers via the radio links at 5 Hz. The R/V Jabba Jaw recorded GPS positions at 1 Hz using an Ashtech Z-Xtreme GPS receiver and Thales choke ring antenna. The R/V Shark recorded GPS positions at a rate of 5 Hz using a Magellan ProFlex 800 GPS receiver and Ashtech marine antenna (table 2).
    For the August SBB surveys (13BIM03) RTK was not used to collect SBB data and all navigation was post-processed to obtain DGPS. The base receivers and the rover receiver recorded their positions concurrently at 1-second (s) intervals throughout the survey. GPS data was acquired and processed in the World Geodetic Datum of 1984 (WGS84) (G1150). Person who carried out this activity:
    U.S. Geological Survey
    Attn: Nancy T. DeWitt
    Geologist
    600 4th Street South
    St. Petersburg, FL
    USA

    (727) 502-8000 (voice)
    ndewitt@usgs.gov
    Date: 2013 (process 2 of 8)
    Single-Beam Bathymetry Acquisition: Depth soundings were acquired aboard the R/V Jabba Jaw and the R/V Shark at 100-milliseconds (ms) using an Odom CV100 echosounder system with a 200 kilohertz (kHz) transducer. Boat motion was recorded on the R/V Jabba Jaw at 50-ms intervals using a Teledyne TSS Dynamic Motion Sensor (TSS DMS-05). The R/V Shark did not record boat motion. To minimize motion errors, the R/V Shark recorded GPS at a high rate (5 Hz) and utilized a short antenna height (lever-arm) in combination with a narrow (4 degree) transducer beam. All sensor data were saved into a single raw data file (.raw) in HYPACK, with each device string referenced by a device identification code and time stamped to Coordinated Universal Time (UTC). Sound velocity measurements were collected using a Valeport mini Sound Velocity Profiler (SVP) to observe changes in water column speed of sound (SOS). Person who carried out this activity:
    U.S. Geological Survey
    Attn: Nancy T. DeWitt
    Geologist
    600 4th Street South
    St. Petersburg, FL
    USA

    (727) 502-8000 (voice)
    ndewitt@usgs.gov
    Date: 2013 (process 3 of 8)
    Swath Bathymetry Acquisition: The IFB data were collected aboard the R/V Sallenger using a SEA SWATHplus-H 468 kHz interferometric sonar system. Boat position and motion were recorded in real-time using a CodaOctopus F190R wetpod inertial measurement unit (IMU) mounted underwater between the transducer heads to minimize lever arm geometry errors between the observed depths and associated vessel motion. Real-time corrected positions were acquired via the use of the Marinestar HP satellite constellation subscription. Marinestar HP position correction data and motion data from the IMU were integrated with interferometric soundings in the SWATHplus software package versions 3.7.17 with positional and calibration offsets pre-defined by a session file (.sxs), allowing for real-time-corrected depths. A Valeport Mini Sound Velocity Sensor (SVS) was attached to the transducer mount and collected continuous speed of sound SOS measurements at the depth of the transducers. These values were directly incorporated into the SWATHplus acquisition software giving real-time speed of sound at the transducer while underway. In addition, a separate sound velocity profiler (Valeport miniSVP) was used to collect speed of sound profiles (water surface to seafloor) at intervals throughout the survey.
    Prior to deployment, all equipment offsets between the sonar head and the DGPS antennas were surveyed in dry dock with the use of a laser total station. All the critical physical measurements between the DGPS antennas and the IMU were entered into the Coda F190R program for calibration. The CodaOctopus F190R was calibrated daily and survey operation would commence once calibration status was considered completed and acceptable. All critical physical measurements between the transducers and the IMU were entered into the SWATHplus configuration file (.sxs) for IFB acquisition. Person who carried out this activity:
    U.S. Geological Survey
    Attn: Nancy T. DeWitt
    Geologist
    600 4th Street South
    St. Petersburg, FL
    USA

    (727) 502-8000 (voice)
    ndewitt@usgs.gov
    Date: 2013 (process 4 of 8)
    Swath Bathymetry Processing: Position data recorded by the Coda-Octopus F190R IMU system were corrected in real time via the Marinestar HP DGPS. The IMU also applied real-time motion corrections for heave, roll, and pitch to the vertical component of each position fix. The corrected positions were then integrated with the observed bathymetric values to calculate a final ellipsoid height and position representing the elevation of the seafloor with respect to the geodetic reference frame ITRF08 across the swath range. SWATHplus serves as both an acquisition software and initial processing software. Preliminary roll calibration trackline data were collected and processed using Systems Engineering and Assessment Ltd. SWATHplus and Grid Processor software version 3.7.17. Instrument offset and calibrations values were input into the session file (.sxs) and the raw data files (.sxr) were then processed using the updated system configuration containing roll calibration values, measured equipment offsets, acquisition parameters, navigation and motion from the F190R, SOS at the sonar head, and SVP cast data. Any calibration offsets or acoustic filtering applied in SWATHplus is also written to the processed data file (.sxp). All processed data files were imported into CARIS HIPS and SIPS version 8.1.7, and the original sounding data were edited for outliers using the program's depth filters and reference surfaces. Any remaining outliers were then edited out manually. A CARIS BASE (Bathymetry with Associated Statistical Error) surface with associated CUBE (Combined Uncertainty and Bathymetry Estimator) sample surface was created from the edited soundings dataset. A BASE hypothesis is the estimated value of a grid node representing all the soundings within a chosen resolution or grid-cell size (for example, 5 m) weighted by uncertainty and proximity; giving the final value as a "sample" of the data within the specific grid cell. This algorithm allows for multiple grid-node hypotheses to be verified or overridden by the user, while maximizing processing efficiency. A 5-m resolution CUBE surface was created to perform initial hypothesis editing using the CARIS Subset Editor tool, followed by higher resolution surface detail editing within subset editor. The sample x,y,z data were exported as ASCII text at a 5 x 5-m sample resolution in the ellipsoid datum of ITRF08. Person who carried out this activity:
    U.S. Geological Survey
    Attn: Nancy T. DeWitt
    Geologist
    600 4th Street South
    St. Petersburg, FL
    USA

    (727) 502-8000 (voice)
    ndewitt@usgs.gov
    Data sources produced in this process:
    • 13BIM02_07_IFB_LEVEL_05_XXX_ITRF08.txt
    Date: 2013 (process 5 of 8)
    Differentially Corrected Navigation Processing: The coordinate values for each of the GPS base stations (TMRK and BRM2) are the time-weighted average of values obtained from the National Geodetic Survey's (NGS) On-Line Positioning User Service (OPUS). Depending on the survey design, the coordinates were utilized either during acquisition to provide RTK navigation, or imported into the post-processing software GrafNav (Waypoint Product Group). For post processing, the kinematic GPS data from the survey vessels were processed to the concurrent GPS data from the base stations. Steps were taken to ensure that the trajectories between the base and rover were clean and resulted in fixed positions. GPS data quality could be monitored and manipulated by analyzing the graphs, trajectory maps, and processing logs that GrafNav produces for each GPS session. If poor GPS data was identified, some common tools used to improve the solution included, but were not limited to, omitting a satellite flagged as poor in health, excluding time-segments with cycle slips, or adjusting the satellite elevation mask angle. The final, differentially-corrected, precise DGPS positions were computed at 1-second (s) intervals for each roving GPS session, and then exported in American Standard Code for Information Interchange (ASCII) text format, which replaced the uncorrected real-time rover positions recorded during acquisition. The GPS data were processed and exported in the World Geodetic System of 1984 (WGS84) (G1150) geodetic datum.
    For USGS cruises 13BIM03 and 13BIM04, RTK navigation was implemented. The OPUS derived base station coordinates were programed into their respective base station GPS receivers and position corrections were broadcasted via radio link to the roving GPS receivers located on each survey vessel. However, 13BIM04 was ultimately post-processed using GrafNav version 8.50 after identification of some unreliable navigation segments. RTK was not implemented during cruise 13BIM08 so navigation data was post-processed using GrafNav version 8.4 and all pertinent base information details were accounted during processing. Data sources produced in this process:
    • Post-processed differential navigation data for the rover (boat) in ASCII text format. 3 files (forward, reverse, and combined trajectories) are produced for each GPS session file.
    Date: 2013 (process 6 of 8)
    Single-beam bathymetry processing: All data were processed using CARIS HIPS and SIPS (Hydrographic Information Processing System and Sonar Information Processing System) version 8.1.5. The raw HYPACK (version 10) data files were imported into CARIS, the differentially corrected navigation files were imported using the generic data parser tool within CARIS, and any SVP profile casts were entered and edited using the SVP editor within CARIS. The bathymetric data components (position, motion, depth, and SOS) were then merged and geometrically corrected in CARIS to produce processed x,y,z data. Next, the data were edited for outliers and then further reviewed in the Subset Editor utility for crossing status, and questionable data points or areas. The geometrically corrected point data were then exported as an x,y,z ASCII text file referenced to WGS84(G1150), equivalent to ITRF00, and ellipsoid height in meters. Person who carried out this activity:
    U.S. Geological Survey
    Attn: Nancy T. DeWitt
    Geologist
    600 4th Street South
    St. Petersburg, FL
    USA

    (727) 502-8000 (voice)
    ndewitt@usgs.gov
    Data sources used in this process:
    • Post-processed differential navigation data files and HYPACK RAW bathymetric data in ASCII text format.
    Data sources produced in this process:
    • 13BIM03_SBB_ITRF00_xyz.zip 13BIM04_SBB_ITRF00_xyz.zip 13BIM08_SBB_ITRF00_xyz.zip
    Date: 2013 (process 7 of 8)
    Datum transformation: Using the transformation software VDatum version 3.3, both the IFB and SBB data were transformed horizontally from their acquisition datums (IBF, ITRF08; SBB, ITRF00) to the North American Datum of 1983 (NAD83) reference frame and the orthometric vertical datum NAVD88 using the National Geodetic Survey (NGS) geoid model of 2009 (GEOID09). Person who carried out this activity:
    U.S. Geological Survey
    Attn: Nancy DeWitt
    Geologist
    600 4th Street South
    St. Petersburg, FL
    USA

    (727) 502-8000 (voice)
    ndewitt@usgs.gov
    Data sources used in this process:
    • 13BIM02_07_ITRF08_xyz.txt 13BIM03_SBB_ITRF00_xyz.txt 13BIM04_SBB_ITRF00_xyz.txt 13BIM08_SBB_ITRF00_xyz.txt
    Data sources produced in this process:
    • 13BIM02_07_NAD83_NAVD88_GEOID09_xyz.txt 13BIM03_SBB_NAD83_NAVD88_GEOID09_xyz.txt 13BIM04_SBB_NAD83_NAVD88_GEOID09_xyz.txt 13BIM08_SBB_NAD83_NAVD88_GEOID09_xyz.txt
    Date: 2013 (process 8 of 8)
    Gridding Bathymetric data: Using Esri ArcGIS version 10.3.1, the swath and the single-beam elevations were examined for spatial distribution and vertical agreement. After combining the point data (x,y,z) a triangulated irregular network (TIN) was generated. The tin surface and elevation point-shapefile were used in conjunction to visually scan for any remaining discrepancies. Once all data were reviewed, a 50 x 50-m cell resolution DEM was generated using the natural neighbor algorithm in ArcGIS software. A raster mask was created from the polygon survey extent using the ArcGIS "polygon to raster" conversion tool. The DEM was then clipped to the raster mask using the ArcGIS Spatial Analyst "extract by raster mask" tool. To help reduce uncertainty in the final DEM, the ArcGIS Spatial Analyst "neighborhood" low pass raster-data filter was applied. Person who carried out this activity:
    U.S. Geological Survey
    Attn: Nancy DeWitt
    Geologist
    600 4th Street South
    St. Petersburg, FL
    USA

    (727) 502-8000 (voice)
    ndewitt@usgs.gov
    Data sources used in this process:
    • 13BIM02_07_NAD83_NAVD88_GEOID09_xyz.txt 13BIM03_SBB_NAD83_NAVD88_GEOID09_xyz.txt 13BIM04_SBB_NAD83_NAVD88_GEOID09_xyz.txt 13BIM08_SBB_NAD83_NAVD88_GEOID09_xyz.txt
    Data sources produced in this process:
    • Chandeleurs_2013_50_NAD83_NAVD88_GEOID09_DEM.tif
  3. What similar or related data should the user be aware of?

How reliable are the data; what problems remain in the data set?

  1. How well have the observations been checked?
    The accuracy of the data is determined during data collection. The SBB and IFB data were collected during concurrent research cruises in July and August of 2013. Methods were employed to maintain data collection consistency aboard various platforms. During mobilization, each piece of equipment (SBB and IFB) is isolated to obtain internal and external offset measurements with respect to the survey platform. Each system has a dedicated computer, and efforts are made to utilize the same equipment and software versions on both systems. However, upgrades and changes occur and require additional setup, measurements, and notation. DGPS was always implemented for navigational accuracy either during acquisition or as a post-processing step. These bathymetric data have not been independently verified for accuracy.
    For the SBB, offsets between the single-beam transducers, the Ashtech antenna reference point (ARP), and the TSS motion unit were measured and accounted for on the rovers. For RTK in July (13BIM03 and 13BIm04) all respective base station parameters and rover parameters including antenna height and antenna models were entered into their respective GPS units. For the August surveys, all pertinent measurements were accounted for in the DGPS post-processing software packages (National Geodetic Survey On-Line Positioning User Service, OPUS, and Waypoint Product Group GrafNav, version 8.3). Bar checks were also performed as calibration efforts and accounted for any drift in the echosounder.
    For the IFB, offsets between the sonar head and the DGPS antennas were measured and entered into the CodaOctopus F190R internal setup program. DGPS was provided through the Marinestar HP wide-area GPS service. All the critical measurements were recorded manually and digitally and entered into their respective programs for calibration. The CodaOctopus F190R was calibrated daily and survey operation would commence once calibration status was considered completed and acceptable.
  2. How accurate are the geographic locations?
    For the single-beam navigation processing, all the static base station sessions were processed through the On-Line Positioning User Service (OPUS) maintained by the National Oceanic and Atmospheric Administration (NOAA) and the National Geodetic Survey (NGS). The base location results from OPUS were entered into a spreadsheet to compute a final, time-weighted positional coordinate (latitude, longitude, and ellipsoid height). Base-station positional error for each GPS session was calculated as the absolute value of the final position minus the session position value. The maximum horizontal error of the base station coordinates used for RTK and or post-processing the SBB was 0.00042 decimal seconds latitude and 0.00096 decimal seconds longitude for the USGS benchmark TMRK, and 0.00015 decimal seconds latitude and 0.00030 decimal seconds longitude for the USGS benchmark BRM2.
    For the interferometric swath bathymetry data collection horizontal navigational accuracy is a result of the Marinestar HP DGPS. The horizontal accuracy of the Marinestar HP navigation subscription is reported by the service as +/-10 cm (95% of the time), http://www.fugromarinestar.com/Products-Services/Services/Marinestar_GPS.
  3. How accurate are the heights or depths?
    All static base station sessions for TMRK and BRM2 were processed through On-Line Positioning User Service (OPUS) maintained by the National Oceanic and Atmospheric Administration (NOAA) and the National Geodetic Survey (NGS). The base location results from OPUS were entered into a spreadsheet to compute a final, time-weighted positional coordinate (latitude, longitude, and ellipsoid height). Base-station positional error for each GPS session was calculated as the absolute value of the final position minus the session position value. SPCMSC standards define the maximum acceptable vertical error for any individual base station GPS session as less than or equal to 3 times the standard deviation of the ellipsoid height; any occupations exceeding this error are removed and the base station coordinates are recalculated. For TMRK base location the standard deviation of the ellipsoid height was 0.014 m and the maximum difference from the average ellipsoid for any GPS session was +/- 0.030 m. For BRM2 base location the standard deviation of the ellipsoid height was 0.013 m and the maximum difference from the average ellipsoid for any GPS session was +/- 0.031 m. All the RTK and the post-processed SBB data (x,y,z) for 2013 are referenced to these base station coordinates. The differentially corrected navigation files (base station GPS processed to boat GPS) were exported from GrafNav version 8.4 and then imported into CARIS HIPS and SIPS version 7.1 and merged by time with the HYPACK (version 10.0.5.31) raw data files at which point the soundings are then geometrically corrected for motion and speed of sound. For the single-beam soundings, elevation differences at 320 crossings were within +/- 0.15 m which accounts for 68 percent of the crossings.
    For the interferometric swath bathymetry data collection the vertical navigational accuracy is a result of the Marinestar HP DGPS. The stated vertical accuracy of the Marinestar HP navigation subscription used during swath bathymetry acquisition is +/-0.15 m (95% of the time), http://www.fugromarinestar.com/Products-Services/Services/Marinestar_GPS. The Coda Octopus F190R IMU, which integrates the Marinestar HP position with motion, measures vessel velocity (+/- 0.014 m/s), roll and pitch (< 0.025 degrees), heading (1-m baseline 0.1 degrees), and heave (5 cm per meter of depth). The vertical accuracy for the SWATHplus-H system varies with depth and across track range. At 57 m it is accurate to 10 cm vertically. Maximum vertical transformation error reported by VDatum is 0.171 m or 17.1 centimeters for eastern Louisiana.
    The sum of the errors (+/- 0.031 m + +/-0.15 m +0.171 m) in the vertical is equal to +/-.352 m or +/- 35.2 cm.
  4. Where are the gaps in the data? What is missing?
    This is a completely processed DEM representing an interpolated bathymetric surface derived from the acoustic interferometric swath and single-beam bathymetry data.
  5. How consistent are the relationships among the observations, including topology?
    The SBB and IFB data were collected during concurrent research cruises in July and August 2013. Refer to the online data series linkage for field logs, vessel platform descriptions, and other survey information. This dataset was created to provide a single post-processed DEM from the merged datasets. The DEM is 50-m cell-size resolution; data gaps between acquisition tracklines are predicted values generated by the gridding algorithm.

How can someone get a copy of the data set?

Are there legal restrictions on access or use of the data?
Access_Constraints: None
Use_Constraints:
The U.S. Geological Survey requests that it be referenced as the originator of this dataset in any future products or research derived from these data. These data should not be used for navigational purposes.
  1. Who distributes the data set? (Distributor 1 of 1)
    U.S. Geological Survey
    Attn: Nancy T. DeWitt
    Geologist
    600 4th Street South
    St. Petersburg, FL
    USA

    (727) 502-8000 (voice)
    ndewitt@usgs.gov
  2. What's the catalog number I need to order this data set? Downloadable data
  3. What legal disclaimers am I supposed to read?
    This publication was prepared by an agency of the United States Government. Although these data have been processed successfully on a computer system at the U.S. Geological Survey, no warranty expressed or implied is made regarding the display or utility of the data on any other system, nor shall the act of distribution imply any such warranty. The U.S. Geological Survey shall not be held liable for improper or incorrect use of the data described and (or) contained herein. Reference herein to any specific commercial product, process, or service by trade name, trademark, manufacturer, or otherwise does not constitute or imply its endorsement, recommendation, or favoring by the United States Government or any agency thereof.
  4. How can I download or order the data?
  5. What hardware or software do I need in order to use the data set?
    The raster contained in the .zip file is available as GeoTIFF. To utilize this data, the user must have a GIS software package capable of reading .tif format.

Who wrote the metadata?

Dates:
Last modified: 2017
Metadata author:
U.S. Geological Survey
Attn: Nancy T. DeWitt
Geologist
600 4th Street South
St. Petersburg, FL
USA

727-502-8000 (voice)
ndewitt@usgs.gov
Metadata standard:
FGDC Content Standard for Digital Geospatial Metadata (FGDC-STD-001-1998)

This page is <https://cmgds.marine.usgs.gov/catalog/spcmsc/Chan13_DEM_metadata.faq.html>
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