Seismic Reflection, EdgeTech SB-424 chirp profile images collected within Lake Powell, UT-AZ during USGS field activity 2017-049-FA (PNG images).

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Frequently anticipated questions:

What does this data set describe?

Seismic Reflection, EdgeTech SB-424 chirp profile images collected within Lake Powell, UT-AZ during USGS field activity 2017-049-FA (PNG images).
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.
Additional information on the field activity is available from
  1. How might this data set be cited?
    U.S. Geological Survey, 2018, Seismic Reflection, EdgeTech SB-424 chirp profile images collected within Lake Powell, UT-AZ during USGS field activity 2017-049-FA (PNG images).: 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:

    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,
  2. What geographic area does the data set cover?
    West_Bounding_Coordinate: -110.892381
    East_Bounding_Coordinate: -110.427431
    North_Bounding_Coordinate: 37.834931
    South_Bounding_Coordinate: 37.162164
  3. What does it look like? (JPEG)
    Thumbnail image of chirp seismic-reflection profile example from Lake Powell, UT-AZ.
  4. Does the data set describe conditions during a particular time period?
    Beginning_Date: 12-Oct-2017
    Ending_Date: 17-Oct-2017
    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, type Pixel
    2. What coordinate system is used to represent geographic features?
  7. How does the data set describe geographic features?
    The PNG seismic reflection images can be hyperlinked to their corresponding trackline or shotpoint locations in ArcGIS using the shapefiles '2017-049-FA_Edgetech424_Tracklines.shp' or '2017-049-FA_Edgetech424_500sht.shp', respectively (available from the larger work citation). The images show two-way travel time (seconds) on the y-axis and distance along profile (annotation at 500 shot intervals) on the x-axis.
    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
    384 Woods Hole Road
    Woods Hole, Massachusetts

    508-548-8700 x2348 (voice)
    508-457-2310 (FAX)

Why was the data set created?

These PNG images represent approximately 92 km of chirp seismic-reflection data collected by the U.S. Geological Survey during survey 2017-049-FA along the San Juan Arm and Good Hope Bay to Hite sections of Lake Powell in the Glen Canyon National Recreation Area. Images of each seismic profile were generated in order to provide portable and easily viewable alternatives to the SEGY versions of the data. Each profile image can be hotlinked to its corresponding trackline navigation contained within the Esri polyline shapefile '2017-049-FA_Edgetech424_Tracklines.shp'. Shotpoint index marks along the top of the PNG images correlate to the positions of 500 shot intervals within the Esri point shapefile '2017-049-FA_Edgetech424_500sht.shp'.

How was the data set created?

  1. From what previous works were the data drawn?
    SEG-Y SB-424 data (source 1 of 1)
    U.S. Geological Survey, Unpublished Material, SB-424 PNG image data.

    Type_of_Source_Media: disc
    Chirp seismic data were collected using an EdgeTech 3100 portable sub-bottom profiling system and an SB-424 towfish (4-24 kHz), which was towed from a port side davit on the R/V Stephens with the transducer approximately 1 m below the water line, and 2.8 meters astern of the DGPS antenna mounted atop the port side of the cabin. Edgetech Discover Sub-Bottom (version 4.04) seismic acquisition software was used to control the 3100 topside unit, digitally log trace data in the SEG-Y Rev. 1 format (IEEE floating point), and record GPS navigation coordinates to the SEG-Y trace headers (in arc seconds of Latitude and Longitude, multiplied by a scalar of 100). Data were acquired using a 250 milliseconds (ms) shot rate, a 10-ms pulse length, and a 4 to 20 kHz frequency sweep. Traces were recorded with a 23-microsecond sample interval over lengths of approximately 236 ms.
  2. How were the data generated, processed, and modified?
    Date: Jun-2018 (process 1 of 2)
    PROCESS STEP 1: SIOSEIS (version 2015.3.1), OpenCPS (version 3.3.0), and Seismic Unix (version 4.2) were used to process SEG-Y data, create navigation files, and plot images. The processing flow and scripts used to produce navigation files including trackline shapefiles are summarized below and in the following processing steps.
    1) SIOSEIS was used to read the raw SEG-Y files, extract the envelope-detected trace, renumber shots starting from one, and write out new SEG-Y files.
    2) OpenCPS was use to run the following flows:
    A) read_segy.flow - SegyTapeRead read the traces. HeaderMath and UTMLatLong were used to convert the source lat/lon positions from seconds of arc to decimal degrees, project them to UTM Zone 12N WGS 84 meters, and write each to new header words (NRP_LAT, NRP_LON, NRP_X, and NRP_Y). DBWrite wrote the UTM positions for the first channel of each FFID to an internal OpenCPS database table. Finally, Output wrote the traces to a new file "*.sht-raw.seis" in the internal OpenCPS format.
    B) layback_shift.flow - Input read the "*.sht-raw.seis" file and sorted the traces to FFID/CHANNEL. The custom Python module ShotlineLayback (developed by Nathan Miller of USGS-WHCMSC) was used to define the measured horizontal offset between the DGPS antenna and the SB-424 transducer (-2.8 m). The algorithm interpolated a sail line from the source shot positions (NRP_X and NRP_Y), then computed layback positions for the SB-424 shots by translating them back along the sail by the measured offset. ApplyStatic was used to shift the traces down by 1.35 ms to account for the approximate 1 m tow depth of the SB-424 (the sound speed of 1480 m/s, a typical value observed from SVP profiles during the survey, was used to convert the depth in meters to 2-way travel time in ms). Output wrote the shifted traces to a new SEG-Y files in which the trace header words SRC_X, SRC_Y represent the calculated layback coordinates, and REC_X, REC_Y maintain the original DGPS coordinates.
    3) The SIOSEIS script Read424 was used to read layback and static corrected SEG-Y files, write a Seismic Unix file, and extract SEG-Y trace header information, including shot number, pre-layback and layback longitude and latitude, year, Julian day, and time of day (UTC). Header information from each SEG-Y file was saved to text files after an AWK (no version) filter was used to maintain the first and last shots, shots at multiples of 100, 500, and shots with unique navigation coordinates. Geographic coordinates (WGS 84) were converted to UTM zone 12 N coordinates (WGS 84) using Proj (version 4.6.0). End shots and shots at multiples of 100 may not have unique navigation coordinates. Separate text files containing the first and last shots and even 500 shot intervals were also saved. A 500 shot interval was chosen because it corresponds to the annotation interval provided along the top of the seismic-reflection profile images. Read424 called a Python script, written by Wayne Baldwin, which imported the CSV files to a Spatialite (version 4.3.0) enabled SQLite (version 3.21.0) database, creating two tables containing point geometries for the unique and 500 shot interval navigation.
    4) The Seismic Unix script Plot424 creates 12-inch-high variable density plots of the seismic profiles, which are converted to PNG format using ImageMagick (version 6.9.5-4). Images show two-way travel time (seconds) along the y-axis (left margin) and shots along profile (labeled at 500 shot intervals) on the x-axis (along top of profile). Person who carried out this activity:
    Wayne E. Baldwin
    U.S. Geological Survey
    384 Woods Hole Rd.
    Woods Hole, MA

    (508) 548-8700 x2226 (voice)
    (508) 457-2310 (FAX)
    Date: 06-Aug-2020 (process 2 of 2)
    Added keywords section with USGS persistent identifier as theme keyword. Person who carried out this activity:
    U.S. Geological Survey
    Attn: VeeAnn A. Cross
    Marine Geologist
    384 Woods Hole Road
    Woods Hole, MA

    508-548-8700 x2251 (voice)
    508-457-2310 (FAX)
  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?
    Although navigation is not stored in the images, positional accuracy is relevant to the accuracy of these data. The EdgeTech SB-424 subbottom profiler was towed from a port side davit on the R/V Stephens with the transducer approximately 1 m below the water line, and 2.8 meters astern of the DGPS antenna mounted atop the port side of the cabin. Navigation data for the SB-424 were collected using a Hemisphere Differential GPS (DGPS) receiver. Positioning data were recorded using Edgetech Discover Sub-Bottom (version 4.04) acquisition software, which logged positioning coordinates to individual trace headers SEG-Y format. DGPS horizontal positional accuracy is assumed to be within 2 m; the layback position of the transducer relative to the DGPS antenna was accounted for during processing.
  3. How accurate are the heights or depths?
  4. Where are the gaps in the data? What is missing?
    Sections of tracklines where navigation was recorded but no seismic data were logged are not included such as during testing, some turns, and very short files. There is no line l1f1.
  5. How consistent are the relationships among the observations, including topology?
    Processed seismic data were converted to PNG format for ease of seismic trace display. Quality control was conducted during processing.

How can someone get a copy of the data set?

Are there legal restrictions on access or use of the data?
Access_Constraints: None
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)
  2. What's the catalog number I need to order this data set? USGS data release 2017-049-FA SB-424 PNG imagery from Lake Powell AZ-UT includes the zip archive containing 10 PNG images named according to line convention, the browse graphic 2017-049-FA_Edgetech424_Images_browse.jpg, and the Federal Geographic Data Committee (FGDC) Content Standards for Digital Geospatial Metadata (CSDGM) metadata file 2017-049-FA_Edgetech424_Images_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?
    These data can be viewed with any PNG image viewing software. The zip files must be uncompressed in order to view the images.

Who wrote the metadata?

Last modified: 06-Aug-2020
Metadata author:
U.S. Geological Survey
Attn: Wayne E. Baldwin
384 Woods Hole Rd.
Woods Hole, MA

(508) 548-8700 x2226 (voice)
(508) 457-2310 (FAX)
Metadata standard:
FGDC Content Standard for Digital Geospatial Metadata (FGDC-STD-001-1998)

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