Coastal Bathymetry and Backscatter Data Collected in June-August 2023 From the Chandeleur Islands, Louisiana

Frequently anticipated questions:

• What does this data set describe?
  1. How might this data set be cited?
  2. What geographic area does the data set cover?
  3. What does it look like?
  4. Does the data set describe conditions during a particular time period?
  5. What is the general form of this data set?
  6. How does the data set represent geographic features?
  7. How does the data set describe geographic features?
• Who produced the data set?
  1. Who are the originators of the data set?
  2. Who also contributed to the data set?
  3. To whom should users address questions about the data?
• Why was the data set created?
• How was the data set created?
  1. From what previous works were the data drawn?
  2. How were the data generated, processed, and modified?
  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?
  2. How accurate are the geographic locations?
  3. How accurate are the heights or depths?
  4. Where are the gaps in the data? What is missing?
  5. How consistent are the relationships among the data, including topology?
• How can someone get a copy of the data set?
  1. Are there legal restrictions on access or use of the data?
  2. Who distributes the data?
  3. What's the catalog number I need to order this data set?
  4. What legal disclaimers am I supposed to read?
  5. How can I download or order the data?
• Who wrote the metadata?

What does this data set describe?

1. How might this data set be cited?
   Stalk, Chelsea A., Bemelmans, Christopher C., and Miselis, Jennifer L., 20250325, Coastal Bathymetry and Backscatter Data Collected in June-August 2023 From the Chandeleur Islands, Louisiana:.

   This is part of the following larger work.
   Stalk, Chelsea A., Bemelmans, Christopher C., and Miselis, Jennifer L., 20250325, Coastal Bathymetry and Backscatter Data Collected in June-August 2023 From the Chandeleur Islands, Louisiana: U.S. Geological Survey data release doi:10.5066/P1NWHXZS, U.S. Geological Survey - St. Petersburg Coastal and Marine Science Center, St. Petersburg, Florida.

   Online Links:

   • https://doi.org/10.5066/P1NWHXZS

2. What geographic area does the data set cover?

   West_Bounding_Coordinate: -89.18871485
   East_Bounding_Coordinate: -89.09223983
   North_Bounding_Coordinate: 29.48448296
   South_Bounding_Coordinate: 29.09223983
   

3. What does it look like?
4. Does the data set describe conditions during a particular time period?

   Beginning_Date: 12-Jun-2023

   Ending_Date: 11-Aug-2023

   Currentness_Reference:

   ground condition

5. What is the general form of this data set?

   Geospatial_Data_Presentation_Form: raster digital data, tabular digital data
   

6. How does the data set represent geographic features?
   1. How are geographic features stored in the data set?
      This is a Point data set. It contains the following vector data types (SDTS terminology):
      • Point (45,543,457)
   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: 0.999600
      Longitude_of_Central_Meridian: -87.000000
      Latitude_of_Projection_Origin: 0.0
      False_Easting: 500000.0
      False_Northing: 0.0
      

      Planar coordinates are encoded using coordinate pair
      Abscissae (x-coordinates) are specified to the nearest 0.6096
      Ordinates (y-coordinates) are specified to the nearest 0.6096
      Planar coordinates are specified in meters
      The horizontal datum used is World Geodetic System of 1984.
      The ellipsoid used is WGS_84.
      The semi-major axis of the ellipsoid used is 6378137.0.
      The flattening of the ellipsoid used is 1/298.257223563.
      

      Vertical_Coordinate_System_Definition:

      Altitude_System_Definition:

      Altitude_Datum_Name: World Geodetic System of 1984
      Altitude_Resolution: 0.001
      Altitude_Distance_Units: meters
      Altitude_Encoding_Method: Attribute values
      

7. How does the data set describe geographic features?

   2023_325_Chandeleurs_MBES_MainAOI_1m_WGS84_UTM16N.xyz

   ASCII text (.txt) file containing the processed 1-m bathymetric grid x,y,z data in the WGS84 [G1150] realization (ellipsoid height) of the main area of interest (AOI), east of Hewes Point. (Source: HYPACK®)

   WGS84_UTM16N_X

   WGS84 UTM Zone 16N X-coordinate (easting) of sample point, in meters. (Source: HYPACK®)

   Range of values
   Minimum:	318941.000
   Maximum:	326520.000
   Resolution:	0.001

   WGS84_UTM16N_Y

   WGS84 UTM Zone 16N Y-coordinate (northing) of sample point, in meters. (Source: HYPACK®)

   Range of values
   Minimum:	3313791.000
   Maximum:	3329030.000
   Resolution:	0.001

   WGS84_Z

   WGS84 (ellipsoid height) of sample point, in meters. (Source: HYPACK®)

   Range of values
   Minimum:	-39.292
   Maximum:	-30.016
   Resolution:	0.001

   TPU

   TPU = Total Propagated Uncertainty, in meters. (Source: Teledyne CARIS™)

   Range of values
   Minimum:	0.040
   Maximum:	0.260
   Resolution:	0.001

   2023_325_Chandeleurs_MBES_SBESCoverage_1m_WGS84_UTM16N.xyz

   ASCII text (.txt) file containing the processed 1-m bathymetric grid x,y,z data in the WGS84 [G1150] realization (ellipsoid height) of a portion of the single-beam (SBES) survey coverage (Lyons and others, 2025) north and west of Hewes Point. (Source: HYPACK®)

   WGS84_UTM16N_X

   WGS84 UTM Zone 16N X-coordinate (easting) of sample point, in meters. (Source: HYPACK®)

   Range of values
   Minimum:	314182.000
   Maximum:	319686.000
   Resolution:	0.001

   WGS84_UTM16N_Y

   WGS84 UTM Zone 16N Y-coordinate (northing) of sample point, in meters. (Source: HYPACK®)

   Range of values
   Minimum:	3319827.000
   Maximum:	3328890.000
   Resolution:	0.001

   WGS84_Ellipsoid_Z

   WGS84 (ellipsoid height) of sample point, in meters. (Source: HYPACK®)

   Range of values
   Minimum:	-37.477
   Maximum:	-32.290
   Resolution:	0.001

   TPU

   TPU = Total Propagated Uncertainty, in meters. (Source: Teledyne CARIS™)

   Range of values
   Minimum:	0.040
   Maximum:	0.256
   Resolution:	0.001

   2023_325_Chandeleurs_MBES_SouthernRecon_1m_WGS84_UTM16N.xyz

   ASCII text (.txt) file containing the processed 1-m bathymetric grid x,y,z data in the WGS84 [G1150] realization (ellipsoid height) offshore of the southernmost Chandeleur Islands. (Source: HYPACK®)

   WGS84_UTM16N_X

   WGS84 UTM Zone 16N X-coordinate (easting) of sample point, in meters. (Source: HYPACK®)

   Range of values
   Minimum:	316450.000
   Maximum:	322444.000
   Resolution:	0.001

   WGS84_UTM16N_Y

   WGS84 UTM Zone 16N Y-coordinate (northing) of sample point, in meters. (Source: HYPACK®)

   Range of values
   Minimum:	3291078.000
   Maximum:	3299262.000
   Resolution:	0.001

   WGS84_Ellipsoid_Z

   WGS84 (ellipsoid height) of sample point, in meters. (Source: HYPACK®)

   Range of values
   Minimum:	-34.787
   Maximum:	-29.487
   Resolution:	0.001

   TPU

   TPU = Total Propagated Uncertainty, in meters. (Source: Teledyne CARIS™)

   Range of values
   Minimum:	0.040
   Maximum:	0.220
   Resolution:	0.001

   2023_325_Chandeleurs_MBES_MainAOI_1m_NAD83_NAVD88_G18.xyz

   ASCII text (.txt) file containing the processed 1-m bathymetric grid x,y,z data in NAD83 [2011], NAVD88, which were derived using the GEOID18 model (orthometric height) of the main area of interest (AOI), east of Hewes Point. (Source: VDatum)

   NAD83_UTM16N_X

   NAD83 UTM Zone 16N X-coordinate (easting) of sample point, in meters. (Source: VDatum)

   Range of values
   Minimum:	318941.85794
   Maximum:	326520.85528
   Resolution:	0.00001

   NAD83_UTM16N_Y

   NAD83 UTM Zone 16N Y-coordinate (northing) of sample point, in meters. (Source: VDatum)

   Range of values
   Minimum:	3313790.42426
   Maximum:	3326029.42104
   Resolution:	0.00001

   NAVD88_GEOID18_Z

   NAVD88 (orthometric height) of sample point, in meters, with respect to GEOID12B. (Source: VDatum)

   Range of values
   Minimum:	-10.962
   Maximum:	-2.020
   Resolution:	0.001

   TPU_WGS84

   Total Propagated Uncertainty, in meters, as reported for WGS84 (G1150) data. A static uncertainty value of 0.065 meters (m) is associated with the transformation of this data. (Source: Teledyne CARIS™)

   Range of values
   Minimum:	0.040
   Maximum:	0.220
   Resolution:	0.001

   2023_325_Chandeleurs_MBES_SBESCoverage_1m_NAD83_NAVD88_G18.xyz

   ASCII text (.txt) file containing the processed 1-m bathymetric grid x,y,z data in NAD83 [2011], NAVD88, which were derived using the GEOID18 model (orthometric height) a portion of the single-beam survey (SBES) coverage (Lyons and others, 2025) north and west of Hewes Point. (Source: VDatum)

   NAD83_UTM16N_X

   NAD83 UTM Zone 16N X-coordinate (easting) of sample point, in meters. (Source: VDatum)

   Range of values
   Minimum:	314182.85875
   Maximum:	319686.85782
   Resolution:	0.00001

   NAD83_UTM16N_Y

   NAD83 UTM Zone 16N Y-coordinate (northing) of sample point, in meters. (Source: VDatum)

   Range of values
   Minimum:	3319826.42345
   Maximum:	3328889.42131
   Resolution:	0.00001

   NAVD88_GEOID18_Z

   NAVD88 (orthometric height) of sample point, in meters, with respect to GEOID12B. (Source: VDatum)

   Range of values
   Minimum:	-9.170
   Maximum:	-4.019
   Resolution:	0.001

   TPU_WGS84

   Total Propagated Uncertainty, in meters, as reported for WGS84 (G1150) data. A static uncertainty value of 0.065 meters (m) is associated with the transformation of this data. (Source: Teledyne CARIS™)

   Range of values
   Minimum:	0.040
   Maximum:	0.260
   Resolution:	0.001

   2023_325_Chandeleurs_MBES_SouthernRecon_1m_NAD83_NAVD88_G18.xyz

   ASCII text (.txt) file containing the processed 1-m bathymetric grid x,y,z data in NAD83 [2011], NAVD88, which were derived using the GEOID18 model (orthometric height) offshore of the southernmost Chandeleur Islands. (Source: VDatum)

   NAD83_UTM16N_X

   NAD83 UTM Zone 16N X-coordinate (easting) of sample point, in meters. (Source: VDatum)

   Range of values
   Minimum:	316450.85608
   Maximum:	322444.85513
   Resolution:	0.00001

   NAD83_UTM16N_Y

   NAD83 UTM Zone 16N Y-coordinate (northing) of sample point, in meters. (Source: VDatum)

   Range of values
   Minimum:	3291077.42993
   Maximum:	3299261.42785
   Resolution:	0.00001

   NAVD88_GEOID18_Z

   NAVD88 (orthometric height) of sample point, in meters, with respect to GEOID12B. (Source: VDatum)

   Range of values
   Minimum:	-7.709
   Maximum:	-2.251
   Resolution:	0.001

   TPU_WGS84

   Total Propagated Uncertainty, in meters, as reported for WGS84 (G1150) data. A static uncertainty value of 0.065 meters (m) is associated with the transformation of this data. (Source: Teledyne CARIS™)

   Range of values
   Minimum:	0.040
   Maximum:	0.220
   Resolution:	0.001

   Entity_and_Attribute_Overview:

   2023_325_Chandeleurs_MBES_MainAOI_1m_Backscatter.tiff, 2023_325_Chandeleurs_MBES_SBESCoverage_1m_Backscatter.tiff, 2023_325_Chandeleurs_MBES_SouthernRecon_1m_Backscatter.tiff: Datasets are GeoTIFFs included in the download file, Chandeleur_Islands_2023_MBES_Backscatter.zip, which is acoustic backscatter intensity data in 32-bit floating point GeoTIFF (.tiff) format with 21229 columns and 19507 rows (min/max [decibels] of -60.21 to 16.8055), 20920 columns and 13168 rows (min/max [decibels] of -45.65 to 18.74), 22452 columns and 12504 rows (min/max [decibels] of -64.91 to 18.7297), respectively. Dataset is projected to the WGS 1984 UTM Zone 18N coordinate system. Backscatter data were collected in three areas: to the east of Hewes Point (referred to as 'MainAOI'), a portion of the single-beam survey coverage (Lyons and others, 2025) north and west of Hewes Point ('SBESCoverage'), and offshore of the southernmost Chandeleur Islands ('SouthernRecon').

   Entity_and_Attribute_Detail_Citation:

   The entity and attribute information were generated by the individual and/or agency identified as the originator of the dataset. Please review the rest of the metadata record for additional details and information.

Who produced the data set?

1. Who are the originators of the data set? (may include formal authors, digital compilers, and editors)
   • Chelsea A. Stalk
   • Christopher C. Bemelmans
   • Jennifer L. Miselis
2. Who also contributed to the data set?
   U.S. Geological Survey, St. Petersburg Coastal and Marine Science Center
3. To whom should users address questions about the data?
   Christopher C. Bemelmans

   U.S. Geological Survey - St. Petersburg Coastal and Marine Science Center

   Electronics Technician (Marine Instrumentation)

   600 4th Street South

   St. Petersburg, FL
   

   USA

   (727)502-8000 (voice)

   cbemelmans@usgs.gov

Why was the data set created?

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: 11-Aug-2023 (process 1 of 4)

   Acquisition: An ERS consisting of multibeam bathymetry was conducted using two Teledyne Reson SeaBat T50-P multibeam echosounders, in dual-head configuration. The pair of Mills Cross (configuration) transmit and receive arrays, were placed side-by-side within a bracket that oriented them at opposing 30-degree angles (relative to horizontal). The bracket was pole-mounted on the starboard gunnel of the research vessel (R/V) Sallenger, a 26-foot fiberglass vessel. The sonar arrays were oriented athwartships (primary and secondary arrays facing outward and down to port and starboard, respectively) and located approximately 1-m below the waterline when deployed. An Applanix Pos MV Wavemaster II V5 inertially aided navigation system was used for timing, positioning, and attitude. The Inertial Measurement Unit (IMU) was mounted atop the sonar bracket just aft of the pole. Two Trimble GA830 Global Navigation Satellite System (GNSS) antennas were affixed atop the cabin approximately amidships of the vessel, two meters apart, port-starboard. An AML Oceanographic Micro-X sound velocity sensor was used for speed of sound readings at the sonar head. A Sontek CastAway CTD was used for measuring sound velocity profiles. Hydrographic survey acquisition and processing software, HYPACK® and HYPACK HYSWEEP® (version 22.3.1.0) managed data inputs from sensors and produced two files (.RAW and .HSX). Data were collected in WGS84 (G1150) Universal Transverse Mercator (UTM) Zone 16 North (16N) coordinates. Multibeam and backscatter data were collected in three areas: to the east of Hewes Point (referred to as 'MainAOI'), a portion of the single-beam survey coverage (Lyons and others, 2025) north and west of Hewes Point ('SBESCoverage'), and offshore of the southernmost Chandeleur Islands ('SouthernRecon'). Multibeam coverage was extended outside of the main AOI to ensure complete coverage of the survey area during the survey period (west, single-beam survey) and to support geophysical data collection (SouthernRecon). Person who carried out this activity:
   

   Christopher C. Bemelmans

   U.S. Geological Survey - St. Petersburg Coastal and Marine Science Center

   600 4th Street South

   St. Petersburg, FL
   

   USA

   (727) 502-8000 (voice)

   cbemelmans@usgs.gov

   Date: 2023 (process 2 of 4)

   Processing: Positioning and attitude data were post-processed in Applanix POSPac MMS (POSPac) software version 8.8 Service Pack 1. Raw position files were imported into POSPac and processed with the IN-Fusion PP-RTX processing mode utilizing Trimble CenterPoint RTX technology (Scherzinger and Hutton, 2025), creating smoothed best estimate of trajectory (SBET) files and dynamic error files (SMRMSG) for each day of the survey. Bathymetric data were post-processed in Teledyne CARIS™ Hydrographic processing software HIPS and SIPS version 11.4.28. HYPACK® acquisition files (.HSX) were first imported into CARIS™ and then post-processed navigation files (SBET and SMRMSG) were imported and applied (Caris, 2015). Additionally, Global Positioning System (GPS) tide (GPS tidal corrections utilize GPS height information from real time survey observations to obtain an ellipsoid height) were applied (IHO, 2019). Sound Velocity Profiles (SVPs) were edited in the SVP editor where all observations from the water line to the sonar heads (1 m water depth) were rejected along with any outlying data. After editing, the SVPs were applied to the sounding data. Roll calibration was also performed, as necessary. TPU was calculated from real time values recorded in the HSX and the SMRMSG files (IHO, 2019). Data were filtered to exclude any points with RESON Quality flags of 0, 1, and 2 (these flags are assigned to individual soundings at the time of acquisition and are a metric of pass/fail in regard to both brightness and collinearity: 0 = fail both, 1 = pass brightness only, 2 = pass collinearity only), as well as soundings that had a TPU greater than stated IHO Special Order standards (IHO, 2008). Refraction artifacts were addressed using Refraction Editor. Further editing was performed in Subset Editor. A 1-m bathymetric CUBE surface was computed and a visual and statistical inspection of the data effecting the surface was performed and edited as needed to serve as quality control (Calder and Wells, 2007). Gaps in the continuous surface were caused by limitations in swath width and planned line navigation within shallow waters. The final surface was exported as an x,y,z ASCII file using the Base Surface to ASCII function. Person who carried out this activity:
   

   Christopher C. Bemelmans

   U.S. Geological Survey - St. Petersburg Coastal and Marine Science Center

   600 4th Street South

   St. Petersburg, FL
   

   USA

   (727) 502-8000 (voice)

   cbemelmans@usgs.gov

   Data sources produced in this process:

   • 2023_325_Chandeleurs_MBES_MainAOI_1m_WGS84_UTM16N.xyz
   • 2023_325_Chandeleurs_MBES_SBESCoverage_1m_WGS84_UTM16N.xyz
   • 2023_325_Chandeleurs_MBES_SouthernRecon_1m_WGS84_UTM16N.xyz

   Date: 2023 (process 3 of 4)

   Acoustic Intensity Backscatter data (.7k) were loaded in CARIS Hydrographic processing software HIPS/SIPS version 11.4.28 using the SIPS Backscatter tool. The final CUBE bathymetry surface serves as input for geometric corrections and average temperature and salinity data (derived from the Sontek CastAway CTD measurements taken during acquisition) are utilized by the program to calculate local absorption and transmission loss. These inputs, along with the following settings were entered into the tool, and then processing was initiated [Weighted Average = blending, image type = beam average, weighting = swath, and an Angle-Varying gain = 200]. During processing, the tool automatically creates a pattern file (.bbp) which is used to correct for variations in the beam pattern of the system. Upon completion, a 1-m backscatter mosaic with intensity values ranging from -17.63 to 3.156 dB (decibels) was created for each survey area. After visual inspection, the mosaic was exported as a 32-bit float GeoTIFF (.tiff) using the surface to GeoTIFF function. Person who carried out this activity:
   

   Christopher C. Bemelmans

   U.S. Geological Survey - St. Petersburg Coastal and Marine Science Center

   600 4th Street South

   St. Petersburg, FL
   

   USA

   (727) 502-8000 (voice)

   cbemelmans@usgs.gov

   Data sources produced in this process:

   • 2023_325_Chandeleurs_MBES_MainAOI_1m_Backscatter.tiff
   • 2023_325_Chandeleurs_MBES_SBESCoverage_1m_Backscatter.tiff
   • 2023_325_Chandeleurs_MBES_SouthernRecon_1m_Backscatter.tiff

   Date: 2023 (process 4 of 4)

   Datum Transformation: Final x,y,z data were converted using NOAA's VDatum v.4.2.2 software conversion tool from the WGS84 [G1150] realization to NAD83 [2011] NAVD88, using the GEOID18 model (orthometric height). Person who carried out this activity:
   

   Christopher C. Bemelmans

   U.S. Geological Survey - St. Petersburg Coastal and Marine Science Center

   600 4th Street South

   St. Petersburg, FL
   

   USA

   (727) 502-8000 (voice)

   cstalk@usgs.gov

   Data sources produced in this process:

   • 2023_325_Chandeleurs_MBES_MainAOI_1m_NAD83_NAVD88_G18.xyz
   • 2023_325_Chandeleurs_MBES_SBESCoverage_1m_NAD83_NAVD88_G18.xyz
   • 2023_325_Chandeleurs_MBES_SouthernRecon_1m_NAD83_NAVD88_G18.xyz

3. What similar or related data should the user be aware of?
   International Hydrographic Organization (IHO), 20191031, The IHO-IOC GEBCO Cook Book: International Hydrographic Organization, Intergovernmental Oceanographic Commission, Monaco.

   Online Links:

   • https://www.gebco.net/data_and_products/gebco_cook_book/

   Other_Citation_Details: pages 81-83
   

   Caris, 20150601, CARIS HIPS and SIPS Training Manual: Caris, Fredericton, NB, Canada.

   Other_Citation_Details: pages 1-446
   

   Scherzinger, Dr. Bruno, and Hutton, Joe, 2025, Applanix IN-Fusion+™: the Ultimate Solution for Enhanced Spatial Intelligence: Trimble, Westminster, Colorado.

   Online Links:

   • https://applanix.trimble.com/en/resources/flipbooks/applanix-in-fusion-plus-the-ultimate-solution-for-enhanced-spatial

   Other_Citation_Details: pages 1-9
   

   Calder, Brian R., and Wells, David E., 20070129, CUBE User's Manual: University of New Hampshire, Center for Coastal and Ocean Mapping, Durham, NH.

   Online Links:

   • https://scholars.unh.edu/ccom/1217

   Other_Citation_Details: pages 1-54
   

   International Hydrographic Organization (IHO), 200802, IHO Standards for Hydrographic Surveys: International Hydrographic Bureau, 4, quai Antoine 1er B.P. 445 - MC 98011 MONACO Cedex Principaute de Monaco.

   Online Links:

   • https://iho.int/uploads/user/pubs/standards/s-44/S-44_5E.pdf

   Other_Citation_Details: pages 1-28
   

   Lyons, Erin O., Stalk, Chelsea A., Miselis, Jennifer L., Buster, Noreen A., Bernier, Julie C., and DeWitt, Nancy T., 20250325, Coastal Single-beam Bathymetry Data Collected in 2023 from the Chandeleur Islands, Louisiana: U.S. Geological Survey data release doi:10.5066/P1HJAVAR, U.S. Geological Survey - St. Petersburg Coastal and Marine Science Center, St. Petersburg, Florida.

   Online Links:

   • https://doi.org/10.5066/P1HJAVAR

   Forde, Arnell S., Miselis, Jennifer L., Stalk, Chelsea A., and Buster, Noreen A., 20240515, Chirp Sub-Bottom Profile Geophysical Data Collected in 2023 From the Chandeleur Islands, Louisiana: U.S. Geological Survey data release doi:10.5066/P1HOLGKM, U.S. Geological Survey - St. Petersburg Coastal and Marine Science Center, St. Petersburg, Florida.

   Online Links:

   • https://doi.org/10.5066/P1HOLGKM

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

1. How well have the observations been checked?
   This dataset was from a single field effort with two survey legs, each with exact instrumentation and set up and were therefore internally consistent. Methods were employed to maintain data collection consistency aboard the platform. During mobilization, each piece of equipment was isolated to obtain internal and external offset measurements with respect to the survey platform. All the critical measurements were recorded manually and digitally entered into their respective programs.
2. How accurate are the geographic locations?
   All data were collected and processed to meet or exceed International Hydrographic Organization (IHO) Special Order standards for positioning and depth (IHO, 2008). Individual Total Propagated Uncertainty (TPU) values associated with each node are available in the x,y,z file, with a mean value of 0.056 m.
3. How accurate are the heights or depths?
   All data were collected and processed to meet or exceed IHO Special Order standards for positioning and depth (IHO, 2008). Individual TPU values associated with each node are available in the x,y,z file, with a mean value of 0.067 m. Data transformed using Vdatum have an additional reported vertical transformation error of 0.065 meters (m).
4. Where are the gaps in the data? What is missing?
   These data are the complete, post-processed x,y,z bathymetric and backscatter data points from multibeam data collected nearshore the Chandeleur Islands, Louisiana, June-August, 2023.
5. How consistent are the relationships among the observations, including topology?
   These files represent the post-processed bathymetric (x,y,z) and acoustic intensity (dB) data during a multibeam bathymetry survey.

How can someone get a copy of the data set?

1. Who distributes the data set? (Distributor 1 of 1)
   
   U.S. Geological Survey, St. Petersburg Coastal and Marine Science Center

   Attn: USGS SPCMSC Data Management

   600 4th Street South

   Saint Petersburg, FL
   

   United States

   727-502-8000 (voice)

   gs-g-spcmsc_data_inquiries@usgs.gov
2. What's the catalog number I need to order this data set? 2023_325_Chandeleurs_MBES_MainAOI_1m_WGS84_UTM16N.xyz, 2023_325_Chandeleurs_MBES_MainAOI_1m_NAD83_NAVD88_G18.xyz, 2023_325_Chandeleurs_MBES_MainAOI_1m_Backscatter.tiff, 2023_325_Chandeleurs_MBES_SBESCoverage_1m_WGS84_UTM16N.xyz, 2023_325_Chandeleurs_MBES_SBESCoverage_1m_NAD83_NAVD88_G18.xyz, 2023_325_Chandeleurs_MBES_SBESCoverage_1m_Backscatter.tiff, 2023_325_Chandeleurs_MBES_SouthernRecon_1m_WGS84_UTM16N.xyz, 2023_325_Chandeleurs_MBES_SouthernRecon_1m_NAD83_NAVD88_G18.xyz, 2023_325_Chandeleurs_MBES_SouthernRecon_1m_Backscatter.tiff
3. What legal disclaimers am I supposed to read?
   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. Any use of trade, firm, or product names is for descriptive purposes only and does not imply endorsement by the U.S. Government.
4. How can I download or order the data?
   • Availability in digital form:

     Data format:	columnar text, GeoTIFF Size: 160
     Network links:	https://coastal.er.usgs.gov/data-release/doi-P1NWHXZS/data/Chandeleur_Islands_2023_MBES_xyz.zip https://coastal.er.usgs.gov/data-release/doi-P1NWHXZS/data/Chandeleur_Islands_2023_MBES_Backscatter.zip

   • Cost to order the data: None

Who wrote the metadata?

Dates:

Last modified: 24-Mar-2025

Metadata author:

U.S. Geological Survey, St. Petersburg Coastal and Marine Science Center

Attn: USGS SPCMSC Data Management

600 4th Street South

Saint Petersburg, FL

United States

727-502-8000 (voice)

gs-g-spcmsc_data_inquiries@usgs.gov

Metadata standard:

Content Standard for Digital Geospatial Metadata (FGDC-STD-001-1998)