Multibeam backscatter data collected within Lake Powell, UT-AZ during USGS Field Activity 2017-049-FA, using a dual-head Reson T20-P multibeam echosounder (8-bit GeoTIFF, UTM Zone 12N, WGS 84, 2 meter resolution)

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Frequently anticipated questions:


What does this data set describe?

Title:
Multibeam backscatter data collected within Lake Powell, UT-AZ during USGS Field Activity 2017-049-FA, using a dual-head Reson T20-P multibeam echosounder (8-bit GeoTIFF, UTM Zone 12N, WGS 84, 2 meter resolution)
Abstract:
High-resolution geophysical mapping of Lake Powell in the Glen Canyon National Recreation Area in Utah and Arizona was conducted between October 8 and November 15, 2017, as part of a collaborative effort between the U.S. Geological Survey and the Bureau of Reclamation to provide high-quality data needed to reassess the area-capacity tables for the Lake Powell reservoir. Seismic data collected during this survey can help to define the rates of deposition within the San Juan and Colorado Rivers, which are the main inflows to Lake Powell. These new data are intended to improve water budget management decisions that affect the natural and recreational resources of the reservoir. Multibeam echosounder bathymetry and backscatter data were collected along 2,312 kilometers of tracklines (331 square kilometers) of the lake floor to regionally define its depth and morphology, as well as the character and distribution of lake-floor sediments. Ninety-two kilometers of seismic-reflection profile data were also collected to define the thickness and structure of sediment deposits near the confluences of the San Juan and Colorado Rivers.
Supplemental_Information:
The elevation of the lake surface during the time of the survey was approximately 1081 meters (WGS ellipsoidal heights), or 1107 meters, (NAVD88) as measured by the Applanix Wavemaster DGPS on the R/V Stephens. Additional information on the field activity is available from https://cmgds.marine.usgs.gov/fan_info.php?fan=2017-049-FA.
  1. How might this data set be cited?
    U.S. Geological Survey, 2018, Multibeam backscatter data collected within Lake Powell, UT-AZ during USGS Field Activity 2017-049-FA, using a dual-head Reson T20-P multibeam echosounder (8-bit GeoTIFF, UTM Zone 12N, WGS 84, 2 meter resolution): data release DOI:10.5066/P90BU2VS, U.S. Geological Survey, Coastal and Marine Geology Program, Woods Hole Coastal and Marine Science Center, Woods Hole, Massachusetts.

    Online Links:

    This is part of the following larger work.

    Andrews, Brian D., Baldwin, Wayne E., Worley, Charles R., Baskin, Robert L., Denny, Jane F., Foster, David S., Irwin, Barry J., Moore, Eric M., and Nichols, Alex R., 2018, High-resolution geophysical data collected in Lake Powell Utah-Arizona, U.S. Geological Survey Field Activity 2017-049-FA: data release DOI:10.5066/P90BU2VS, U.S. Geological Survey, Reston, VA.

    Online Links:

    Other_Citation_Details:
    Suggested citation: Andrews, B.D., Baldwin, W.E., Worley, C.R., Baskin, R.L., Denny, J.F., Foster, D.S., Irwin, B.J., Moore, E.M., and Nichols, A.R., 2018, High-resolution geophysical data collected in Lake Powell, Utah-Arizona, U.S. Geological Survey Field Activity 2017-049-FA: U.S. Geological Survey data release, https://doi.org/10.5066/P90BU2VS.
  2. What geographic area does the data set cover?
    West_Bounding_Coordinate: -111.5601
    East_Bounding_Coordinate: -110.3892
    North_Bounding_Coordinate: 37.84101
    South_Bounding_Coordinate: 36.89187
  3. What does it look like?
    https://www.sciencebase.gov/catalog/file/get/5ba3cc6de4b08583a5c81bbf/?name=2017-049-FA_T20P_Backscatter_2m_browse.jpg (JPEG)
    Thumbnail image of 2-m multibeam echosounder backscatter data collected within Lake Powell, UT-AZ.
  4. Does the data set describe conditions during a particular time period?
    Beginning_Date: 08-Oct-2017
    Ending_Date: 15-Nov-2017
    Currentness_Reference:
    data were collected on the following dates: 20171008-20171022 (Julian day 281-295); 20171024-20171109 (Julian day 297-313); 20171115 (Julian day (319).
  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 52564 x 51513 x 1, type Pixel
    2. What coordinate system is used to represent geographic features?
      Grid_Coordinate_System_Name: Universal Transverse Mercator
      Universal_Transverse_Mercator:
      UTM_Zone_Number: 12N
      Transverse_Mercator:
      Scale_Factor_at_Central_Meridian: 0.9996
      Longitude_of_Central_Meridian: -111
      Latitude_of_Projection_Origin: 0
      False_Easting: 500000
      False_Northing: 0
      Planar coordinates are encoded using row and column
      Abscissae (x-coordinates) are specified to the nearest 2.0
      Ordinates (y-coordinates) are specified to the nearest 2.0
      Planar coordinates are specified in meters
      The horizontal datum used is WGS_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.
  7. How does the data set describe geographic features?
    Entity_and_Attribute_Overview:
    Acoustic reflectance values of the submerged portions of Lake Powell located in Glen Canyon National Recreation Area. No data value = 0.
    Entity_and_Attribute_Detail_Citation: U.S. Geological Survey

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?
  3. To whom should users address questions about the data?
    U.S. Geological Survey
    Attn: Brian Andrews
    Geographer
    384 Woods Hole Road
    Woods Hole, Massachusetts
    US

    508-548-8700 x2348 (voice)
    508-457-2310 (FAX)
    bandrews@usgs.gov

Why was the data set created?

This multibeam backscatter mosaic of Lake Powell will be used in conjunction with other geophysical and sample data to investigate the morphology and geologic framework of the lake bed.

How was the data set created?

  1. From what previous works were the data drawn?
    RAW RESON T20-P MULTIBEAM ECHOSOUNDER FILES (source 1 of 1)
    U.S. Geological Survey, Unpublished Material, raw MBES data in s7k format.

    Type_of_Source_Media: disc
    Source_Contribution:
    Multibeam echosounder (MBES) bathymetry data were collected using dual-head Reson T20-P sonars. The pair of mills cross transmit and receive arrays were mounted 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 side of the R/V Stephens so that the sonar arrays were oriented athwart ships (primary and secondary arrays facing outward and down to port and starboard, respectively) and located approximately 1.235 m below the waterline when deployed. Vessel navigation and attitude data were acquired using an Applanix POS MV Wavemaster (model 220, V5) configured with two AeroAntenna Technologies GPS antennas located at either end of a 2-m baseline, which was oriented fore and aft and mounted atop the MBES pole approximately midships on the starboard side of vessel, and the wetpod MRU mounted atop the sonar bracket just aft of the pole. An AML Micro X SV mounted on the sonar bracket monitored sound speed near the sonars during acquisition, and an AML Minos X SVPT deployed using an electric downrigger mounted on the port quarter was used to collect water column sound speed profiles 1 to 3 times each survey day (See shapefile 2017-049-FA_MVPdata.shp available from the larger work citation). The Reson SeaBat User Interface (version 5.0.0.6) was used to control the sonars, which were operated in intermediate mode at full power (220 db), with frequency-modulated pulses between 200 to 300 kHz. The range of the 1024 across track beams formed by the sonars were adjusted manually depending on water depth, and resulted in combined swath widths of 60 to 200 meters or typically 3 to 6 times the water depth. Data were monitored and recorded using the Reson SeaBat User Interface (UI) (version 5.0.0.6) and Hypack/Hysweep (version 2017, 17.1.3.0). The SeaBat User Interface logged the navigation, attitude, bathymetry, time-series backscatter, and water column data to s7k format files for each sonar. The line files were created by the Reson UI using the following naming convention: YYYYMMDD_HHMMSS_M/S. The line files were appended with a "M" and "S" suffix to denote the port (primary) "M" and "S" starboard (or secondary) sonar heads.
  2. How were the data generated, processed, and modified?
    Date: Nov-2017 (process 1 of 3)
    PROCESSING STEP 1: CARIS HIPS DATA PROCESSING. Multibeam bathymetry processing within CARIS HIPS (version 10.2) during the survey consisted of the following flow:
    1) Vessel configuration files were created in CARIS for the port ("M"=main, or primary) and starboard ("S"=secondary) sonars (RVStephens_DualT20P_M.hvf, and RVStephens_DualT20P_S.hvf) which included relevant, linear and angular installation offsets for each T20-P unit as well as vendor specified uncertainty values for each of the survey sensors.
    2) A CARIS HIPS project (version 10.2) was created with projection information set to Universal Transverse Mercator (UTM) Zone 12N, WGS 84. Separate HIPS projects were created for the Port (M), and Starboard (S) line files using the two vessel configuration files in #1 above.
    3) Each Reson s7k file (M and S) were imported to the new CARIS projects (M and S respectively) using the Import/Conversion Wizard.
    4) Delayed heave data from raw POS MV files were used to update HIPS survey lines using the import auxiliary data function.
    5) Navigation was reviewed and edited as needed using the Navigation Editor tool.
    6) Sound velocity correction was applied using the CARIS algorithm, a master SVP file containing all the sound velocity profiles collected during the survey and specifying the nearest in distance method, delayed heave source, and use surface sound speed.
    7) Data were merged selecting no tide and the delayed heave source.
    8) 2-m resolution Swath Angle Weighted (SWATH) surfaces were created to incorporate all the files (M and S) as they were processed, and the SWATH surfaces were reviewed for inconsistencies and anomalies.
    9) The swath and subset editors were used to remove spurious points through manual editing and filter application, and the refraction editor was used to adjust sound speed values in areas where velocimeter data did not adequately correct depth profiles, which were obviously influenced by local anomalies in speed of sound through the water column.
    10) Survey lines adjusted for refraction anomalies were remerged, and the respective SWATH surfaces were recomputed to reflect the changes. Processing during the survey was primarily focused on QA/QC during acquisition. Editing processes did require trial and error, and were at times iterative. The contact person for this and all subsequent processing steps below is Brian Andrews. Person who carried out this activity:
    U.S. Geological Survey
    Attn: Brian Andrews
    Geographer
    384 Woods Hole Rd.
    Woods Hole, MA

    508-548-8700 x2348 (voice)
    508-457-2310 (FAX)
    bandrews@usgs.gov
    Date: Jul-2018 (process 2 of 3)
    PROCESSING STEP 2: APPLY POST PROCESSED SBET FILES AND EDIT SOUNDINGS. Post-survey processing within CARIS HIPS (version 10.4) consisted of the following flow:
    1) Post-processed navigation, vessel attitude, and GPS height data from POSPac SBET files, and post-processed RMS attitude error data from POSPac smrmsg files were used to update HIPS survey lines using the import auxiliary data function.
    2) Navigation source was set to Applanix SBET, and navigation was reviewed and edited as needed using the Navigation Editor tool.
    3) GPS tide was computed using delayed heave data, the vessel water line, and a single datum value of 0 m (vertically referencing the data to the WGS 84 Ellipsoid).
    4) Sound velocity correction was reapplied using the CARIS algorithm, the master SVP file containing all the sound velocity profiles collected during the survey and specifying the nearest in distance method, delayed heave source, and use surface sound speed.
    5) Data were remerged selecting the GPS tide and delayed heave sources.
    6) 2-m resolution SWATH surfaces using both the M and S files were created using the Swath Angle method and a maximum footprint of 9.
    7) Additional editing was conducted using the swath and subset editors to minimize inconsistencies and artifacts, and the SWATH surface was recomputed to reflect the changes. Finally, small "no data" holidays were filled using the "Fill Raster Holiday" tool and a 5x5 cell filter using data from a minimum of 5 neighboring cells.
    Date: Jul-2018 (process 3 of 3)
    PROCESSING STEP 3: QPS FMGT PROCESSING
    Backscatter mosaics were created using QPS FMGT (v. 7.7.5) processing software. Raw s7k files containing the time series values, were paired with the HIPS line files that contained the depth data to create a two meter resolution time series backscatter mosaic that followed the steps below.
    1) Create new FMGT projects for northeast, and southwest sections of Lake Powell using UTM 12N, WGS 84 coordinate system.
    2) Set processing parameters for T20-P Sonar (defaults)
    3) Set filter method to flat 300
    4) Add source/paired files using the s7k for the backscatter files, and the "processed.depth" files from the HIPS line file directory. All the s7k and HIPS files were added by Julian day. Once the line files were added to the project a two meter draft mosaic was created using the "time-series" as the backscatter source for each Julian day for review.
    5) A final two-meter mosaic was created and visually reviewed for inconsistencies or anomalies. Individual line files were moved to up or down in the mosaic order to increase quality if needed. The "Backscatter Adjustment" tool was used to increase or decrease intensity of individual lines as required to match adjacent lines.
    6) The resulting mosaic was exported out of FMGT as an 8-bit gray-scale GeoTIFF.
  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?
    Navigation data were acquired using the WGS 84 coordinate system with an Applanix POS MV Wavemaster (model 220, V5), which blends Global Navigation Satellite Systems (GNSS) with acceleration data from a Motion Reference Unit (MRU) and GPS azimuthal heading. The POS MV was configured with two AeroAntenna Technologies GPS antennas located at either end of a 2-m baseline, which was oriented fore and aft and mounted atop the MBES pole, approximately midships on the starboard side of vessel. DGPS positions were obtained from the primary antenna located on the forward end of the baseline, and the positional offsets between the antenna and the navigational reference point (the POS MV IMU) were accounted for in the Applanix POSView (version 8.60) acquisition software. DGPS positions are horizontally accurate to 0.5 - 2 meters, but accuracy can increase to less than 10 cm after post-processing with Applanix POSPac (version 8.1).
  3. How accurate are the heights or depths?
  4. Where are the gaps in the data? What is missing?
    Data were not collected on October 23, 2017 while the base of operations was moved from Bullfrog, UT in the northeast to Page, AZ in the southwest. Data were not collected between Nov 10 and 14 because of a cable failure of the Applanix navigation and attitude system. Operations resumed (and were completed) November 15, 2017 after installation of the new cable. These data have not been ground validated with lakebed sediment samples.
  5. How consistent are the relationships among the observations, including topology?
    This backscatter mosaic represents processed dual-head Reson T20-P multibeam echosounder (MBES) time series data gridded at 2-m resolution. Quality control and data processing were conducted to remove spurious points and reduce sound speed artifacts (refraction) using Computer Aided Resource Information System (CARIS) Hydrographic Information Processing System (HIPS; versions 10.2 and 10.4). Despite this processing, small areas of vessel motion and refraction artifacts remain in the data, particularly in deeper areas of the Colorado River. The small slot canyons terminating in the Colorado River presented several challenges to acoustic survey methods. The deep, sinuous canyons such as Rainbow Bridge, Navajo, and Wetherill Canyons are characterized by steep walls with overhangs, above-and below-the lake surface. The overhangs above the surface interfered with the GPS signal at times, requiring detailed editing of the navigation within these areas. The canyon wall overhangs beneath the lake surface produced multipathing of the acoustic signal that required significant editing to minimize the multipath artifact. Small "no data" gaps exist throughout the dataset. These are the result of editing the artifacts and, in some areas, eliminating low quality soundings. In addition, gaps exist in shallow areas where underwater obstructions created hazards for the safe navigation of the survey vessel. Despite editing of the attitude data, vertical offsets between adjacent lines still exist due to equipment malfunctions at the end of the survey in Wahweap and Warm Springs Bays.

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:
Public domain data from the U.S. Government are freely re-distributable with proper metadata and source attribution. Please recognize the U.S. Geological Survey as the originator of the dataset.
  1. Who distributes the data set? (Distributor 1 of 1)
    U.S. Geological Survey - ScienceBase
    Denver Federal Center
    Denver, CO

    1-888-275-8747 (voice)
    sciencebase@usgs.gov
  2. What's the catalog number I need to order this data set? Multibeam backscatter data collected within Lake Powell UT-AZ during USGS Field Activity 2017-049-FA, using a dual-head Reson T20-P multibeam echosounder: includes the GeoTIFF image 2017-049-FA_T20P_Backscatter_2m.tif, the browse graphic 2017-049-FA_T20P_Backscatter_2m_browse.jpg, and Federal Geographic Data Committee (FGDC) Content Standards for Digital Geospatial Metadata (CSDGM) metadata files (2017-049-FA_T20P_Backscatter_2m_meta.xml)
  3. What legal disclaimers am I supposed to read?
    Neither the U.S. Government, the Department of the Interior, nor the USGS, nor any of their employees, contractors, or subcontractors, make any warranty, express or implied, nor assume any legal liability or responsibility for the accuracy, completeness, or usefulness of any information, apparatus, product, or process disclosed, nor represent that its use would not infringe on privately owned rights. The act of distribution shall not constitute any such warranty, and no responsibility is assumed by the USGS in the use of these data or related materials. Any use of trade, product, or firm 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?
  5. What hardware or software do I need in order to use the data set?
    To utilize these data, the user must have software capable of viewing GeoTIFF files.

Who wrote the metadata?

Dates:
Last modified: 25-Oct-2018
Metadata author:
U.S. Geological Survey
Attn: Brian Andrews
Geographer
384 Woods Hole Rd.
Woods Hole, MA

(508) 548-8700 x2348 (voice)
(508) 457-2310 (FAX)
bandrews@usgs.gov
Metadata standard:
FGDC Content Standards for Digital Geospatial Metadata (FGDC-STD-001-1998)

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