Ofu, American Samoa, wave and water level data, 2020

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Frequently anticipated questions:

What does this data set describe?

Title: Ofu, American Samoa, wave and water level data, 2020
Time series data of wave height and water surface elevation were acquired for 399 days at four locations on the southern reef of Ofu, American Samoa, in support of a study on submarine groundwater dynamics on this reef within the National Park of American Samoa’s Ofu Unit. The relative placement of sensors on the reef were as follows: OFU20E03 – mid reef at East site; OFU20E04 – inner reef at East site; OFU20W03 – mid reef at West site; OFU20W04 – inner reef at West site.
Additional information about the field activity or activities from which these data were derived is available online at:
Any use of trade, product, or firm names is for descriptive purposes only and does not imply endorsement by the U.S. Government.
  1. How might this data set be cited?
    Rosenberger, Kurt J., Cheriton, Olivia M., and Storlazzi, Curt D., 20240123, Ofu, American Samoa, wave and water level data, 2020: data release DOI:10.5066/P9RYN5NH, U.S. Geological Survey, Pacific Coastal and Marine Science Center, Santa Cruz, California.

    Online Links:

    This is part of the following larger work.

    Rosenberger, Kurt J., Cheriton, Olivia M., and Storlazzi, Curt D., 2023, Cross-reef wave and water level data from coral reef environments: data release DOI:10.5066/P9RYN5NH, U.S. Geological Survey, Pacific Coastal and Marine Science Center, Santa Cruz, CA.

    Online Links:

    Suggested Citation: Rosenberger, K.J., Cheriton, O.M., and Storlazzi, C.D., 2020, Cross-reef wave and water level data from coral reef environments (ver. 3.0, January 2024): U.S. Geological Survey data release, https://doi.org/10.5066/P9RYN5NH.
  2. What geographic area does the data set cover?
    West_Bounding_Coordinate: -169.7
    East_Bounding_Coordinate: -169.6
    North_Bounding_Coordinate: -14.1
    South_Bounding_Coordinate: -14.2
  3. What does it look like?
    https://www.sciencebase.gov/catalog/file/get/64ef7cadd34e4b6d8ab72c8b?name=ofu2020_map_cropped.jpg&allowOpen=true (JPEG)
    Google Earth image showing Ofu Island and location of instruments.
  4. Does the data set describe conditions during a particular time period?
    Beginning_Date: 05-Feb-2020
    Ending_Date: 10-Mar-2021
    ground condition at time data were collected
  5. What is the general form of this data set?
    Geospatial_Data_Presentation_Form: NetCDF files
  6. How does the data set represent geographic features?
    1. How are geographic features stored in the data set?
      Data were collected continuously along survey transects. Refer to self-contained NetCDF files for more location information.
    2. What coordinate system is used to represent geographic features?
      Horizontal positions are specified in geographic coordinates, that is, latitude and longitude. Latitudes are given to the nearest 0.00001. Longitudes are given to the nearest 0.00001. Latitude and longitude values are specified in Decimal degrees. The horizontal datum used is North American Datum of 1983 (NAD 1983).
      The ellipsoid used is WGS_1984.
      The semi-major axis of the ellipsoid used is 6378137.0.
      The flattening of the ellipsoid used is 1/298.257223563.
      Altitude_Datum_Name: Mean sea level
      Altitude_Resolution: 0.1
      Altitude_Distance_Units: meters
      Explicit elevation coordinate included with horizontal coordinates
  7. How does the data set describe geographic features?
    NetCDF files are self-contained and attribute information may be found in the header of the file itself.
    The entity and attribute information was 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)
    • Kurt J. Rosenberger
    • Olivia M. Cheriton
    • Curt D. Storlazzi
  2. Who also contributed to the data set?
    Eric K. Brown, National Park of American Samoa
  3. To whom should users address questions about the data?
    U.S. Geological Survey, Pacific Coastal and Marine Science Center
    Attn: PCMSC Science Data Coordinator
    2885 Mission Street
    Santa Cruz, CA

    831-427-4747 (voice)

Why was the data set created?

The measurements of waves and water levels from these instrument deployments provide information on the variability of waves on the coral reefs of southern Ofu. These data will be used to study the transformation of waves over the reef and how this process contributes to water levels, runup and the potential for flooding of the coast. They will also be used to support analyses into submarine groundwater dynamics on this reef.

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: 2023 (process 1 of 2)
    The RBR solo D|wave instruments operated in burst-sampling mode; they measured pressure as 4096 samples collected at 2 Hz every hour (approximately 34-min long bursts). Raw data from each instrument were exported to ASCII text files using the manufacturers software, RBR Ruskin v2.20.4, on a Personal Computer running Windows 10 Enterprise. Exported data were QA/QC’d in Matlab R2020a and exported to netCDF using Python 3.9. Data records were trimmed to a uniform start time chosen according to the earliest instrument deployment; as a result, some records still retain some out-of-water periods. The raw pressure readings include the pressure from both the overlying water and the atmosphere, and therefore must be corrected to remove the atmospheric pressure. Data on atmospheric pressure were downloaded from a local weather station maintained by the National Oceanic and Atmospheric Administration (American Samoa Observatory (SMO) on the northeastern tip of Tutuila Island, American Samoa, https://gml.noaa.gov/obop/smo/). The data on barometric pressure were interpolated to the burst interval of the pressure measurements, and a single value was removed from each burst.
    Date: 2023 (process 2 of 2)
    Files are named with a convention that uses a 11-digit alpha-numeric code. The first three characters for this dataset are all 'OFU' for the experiment name; the fourth and fifth positions represent the calendar year in which the first data point in the file was taken (20, 2020); the sixth, seventh and eighth characters are an alphanumeric code for the site name (W03, W04 etc.); the ninth and tenth characters represent the instrument position on the platform, where 01 is the top-most. The eleventh character ‘b’ indicates that these are the raw burst data. The ‘-cal’ suffix indicates the processing level (‘cal’, calibrated, or translated into scientific units, provisional status).
  3. What similar or related data should the user be aware of?
    Cheriton, Olivia M., Storlazzi, Curt D., Rosenberger, Kurt J., Oberle, Ferdinand K.J., and Brown, Eric K., 2024, Extreme Low-Frequency Waves on the Ofu, American Samoa, Reef Flat.

    Online Links:

    Cheriton, OM, Storlazzi, CD, Oberle, FKJ, Rosenberger, KJ, and Brown, EK (2024) Extreme low-frequency waves on the Ofu, American Samoa, reef flat. Coral Reefs, https://doi.org/10.1007/s00338-023-02453-w

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

  1. How well have the observations been checked?
    Data were visually inspected for quality, but generally all data are included in time series.
  2. How accurate are the geographic locations?
    A formal accuracy assessment of the horizontal positional information in the data set has not been conducted. Stated accuracy of the GPS unit used to geolocate the instrument package is +/- 5 m.
  3. How accurate are the heights or depths?
    No formal assessment of vertical accuracy was performed. The stated accuracy of the pressure sensor on the wave gauge is +/- 0.01 decibars, which is approximately equivalent to 0.01 meters.
  4. Where are the gaps in the data? What is missing?
    Dataset is considered complete for the information presented, as described in the abstract. The inner-reef instrument at the East site stopped collecting data earlier than the other instruments (December 1, 2020). The inner-reef instrument at the West site (OFU20W04) had an incomplete burst on September 14, 2020 at 15:00; this burst was removed. Users are advised to read the rest of the metadata record carefully for additional details.
  5. How consistent are the relationships among the observations, including topology?
    Data fall within expected ranges.

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 USGS-authored or produced data and information are in the public domain from the U.S. Government and are freely redistributable with proper metadata and source attribution. Please recognize and acknowledge the U.S. Geological Survey and the National Park of American Samoa as the originator(s) of the dataset and in products derived from these data.
  1. Who distributes the data set? (Distributor 1 of 1)
    U.S. Geological Survey - ScienceBase
    Denver Federal Center, Building 810, Mail Stop 302
    Denver, CO

    1-888-275-8747 (voice)
  2. What's the catalog number I need to order this data set? These data are available in binary netCDF format.
  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 on any other system or for general or scientific purposes, nor shall the act of distribution constitute any such warranty.
  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 the NOAA netCDF file viewer, ncBrowse, which can be downloaded from the internet at https://www.nodc.noaa.gov/gtspp/software/ncbrowse/index.html.

Who wrote the metadata?

Last modified: 23-Jan-2024
Metadata author:
U.S. Geological Survey, Pacific Coastal and Marine Science Center
Attn: PCMSC Science Data Coordinator
2885 Mission Street
Santa Cruz, CA

831-427-4747 (voice)
Metadata standard:
Content Standard for Digital Geospatial Metadata (FGDC-STD-001-1998)

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