Alexander G. Snyder Cordell D. Johnson Ann E. Gibbs Li H. Erikson 20210719 comma-delimited text data release DOI:10.5066/P9238F8K Pacific Coastal and Marine Science Center, Santa Cruz, California U.S. Geological Survey https://doi.org/10.5066/P9238F8K https://www.sciencebase.gov/catalog/item/60c24fbad34e86b9389559b8 This data release presents nearshore bathymetry data collected at the mouth of the Unalakleet River in Alaska, near the city of Unalakleet. The data were collected in August 2019 by the U.S. Geological Survey, Pacific Coastal and Marine Science Center. Nearshore bathymetry was measured along survey lines from the shore to a depth of approximately -7.4 m NAVD88 and in a portion of the estuary closest to the mouth. Bathymetry data were collected using small boat equipped with a single-beam sonar system and global navigation satellite system (GNSS) receiver. The sonar system consisted of an Odom Echotrac CV-100 single-beam echosounder and 200 kHz transducer with a 9-degree beam. Depths from the seafloor to the echosounder were calculated using the digitized acoustic backscatter and sound velocity profiles, measured in multiple locations using a YSI CastAway CTD. The position of the boat and echosounder was recorded at 10 Hz using a Trimble R7 receiver and Zephyr 2 antenna. Survey-grade vertical and horizontal positions were achieved by applying differential corrections from a nearby GNSS base station installed for the purposes of this survey. Data were collected to create a digital elevation model of the nearshore bathymetry for use in coastal flooding models. These data are intended for science researchers, students, policy makers, and the general public. These data can be used with geographic information systems or other software to identify shallow-water bathymetric features. Additional information about the field activity from which these data were derived is available online at: https://cmgds.marine.usgs.gov/fan_info.php?fan=2019-629-FA Any use of trade, product, or firm names is for descriptive purposes only and does not imply endorsement by the U.S. Government. Although this Federal Geographic Data Committee-compliant metadata file is intended to document the data set in nonproprietary form, as well as in Esri format, this metadata file may include some Esri-specific terminology. 20190709 20190712 ground condition at time data were collected Complete None planned -160.863919 -160.766694 63.881365 63.846674 ISO 19115 Topic Category elevation Data Categories for Marine Planning Bathymetry and Elevation USGS Thesaurus bathymetry bathymetry measurement GPS measurement Marine Realms Information Bank (MRIB) keywords single-beam echo sounder Global Positioning System (GPS) observations None U.S. Geological Survey USGS Coastal and Marine Hazards and Resources Program CMHRP Pacific Coastal and Marine Science Center PCMSC USGS Metadata Identifier USGS:60c24fbad34e86b9389559b8 Geographic Names Information System (GNIS) Norton Sound Pacific Ocean Unalakleet City of Unalakleet Unalakleet River State of Alaska Nome Census Area none 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 as the originator of the dataset and in products derived from these data. This information is not intended for navigation purposes. U.S. Geological Survey, Pacific Coastal and Marine Science Center PCMSC Science Data Coordinator mailing and physical

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Santa Cruz CA 95060 831-427-4747 pcmsc_data@usgs.gov MATLAB Version: 8.6.6.958874 (R2015b) International Hydrographic Organization (IHO) 2008 https://iho.int/uploads/user/pubs/Drafts/S-44_Edition_6.0.0-Final.pdf No formal attribute accuracy tests were conducted. All data falls within expected ranges. Dataset is considered complete for the information presented, as described in the abstract. Users are advised to read the rest of the metadata record carefully for additional details. Survey-grade positions of the small boat were achieved with global navigation satellite system (GNSS) receivers and a single GNSS base station. The position of the GNSS base station was derived from four static GNSS occupations from July 7 to July 12, 2019, with durations ranging from 3 to 13 hours. The static observations were processed using the National Geodetic Survey Online Positioning User Service (OPUS) and averaged to derive the final base station coordinates relative to the North American Datum of 1983 (2011 realization). Positioning data from the survey vessels were post-processed using Waypoint Grafnav to apply differential corrections from the GNSS base station. Manufacturer reported accuracy for the differentially corrected horizontal positions for the GNSS rover trajectories is 0.8 cm + 0.5 ppm. Baselines from the GNSS base station varied between 0.1 km and 4.5 km with a mean of 1 km, suggesting the average horizontal accuracy of survey vessel positions to be about 1 cm. Uncertainty in the horizontal positions associated with pitch and roll of the survey vessels is unknown. Uncertainty in the final elevations is derived from the combination of uncertainty in the GNSS positioning and bathymetric sounding measurements. Manufacturer reported accuracy for the differentially corrected vertical positions for the GNSS rover trajectories is 1.5 cm + 1 ppm relative to the benchmark elevation. Baselines from the GNSS base station varied between 0.1 m and 4.5 km with a mean of 1 km, suggesting the average vertical accuracy of survey vessel positions to be about 2.5 cm. The manufacturer of the single-beam echosounder used in this study reports a vertical accuracy of 1 cm. Additional uncertainty in the final computed elevations data is related to unmeasured variability in the speed of sound used to compute depths from bathymetric soundings and, thus, is depth-dependent. Based on analysis of available speed of sound measurements, we estimate uncertainties in the final depth soundings to be no greater than 1 percent of the water depth. The total vertical uncertainty is calculated using the constant- and depth-dependent factors summed in quadrature (International Hydrographic Organization, 2008). The vertical uncertainty in final elevations varied between 3 cm and 8 cm with a mean vertical uncertainty of 4 cm. Uncertainty in the vertical positions associated with pitch and roll of the survey vessels is unknown. Bathymetry data were collected between July 9 and July 12, 2019, using a single-beam sonar system and global navigation satellite system (GNSS) receiver mounted on a small boat. The sonar system consisted of an Odom Echotrac CV-100 single-beam echosounder and 200 kHz transducer with a 9-degree beam angle. Raw acoustic backscatter returns were digitized by the echosounder with a vertical resolution of 1.25 cm. Depths from the echosounder was computed using sound velocity profiles measured using a YSI CastAway CTD during the survey. Positioning of the survey vessel was determined at 10 Hz using survey-grade GNSS receiver. Output from the GNSS receiver and sonar system were combined in real time on the small boat by a computer running HYPACK hydrographic survey software. Navigation information was displayed on a computer monitor, allowing the boat operator to navigate along survey lines at speeds of 2 to 3 m/s. 20190712 Survey-grade positions were achieved with a single-base station and differential post-processing. The position of the GNSS base station was derived from four static GNSS occupations from July 7 to July 12, 2019, with durations ranging from 3 to 13 hours. The static observations were processed using the National Geodetic Survey Online Positioning User Service (OPUS) and averaged to derive the final base station coordinates relative to the North American Datum of 1983 (2011 realization). Positioning data from the survey vessel’s GNSS receiver were post-processed using Waypoint Grafnav to apply differential corrections from the GNSS base station. Orthometric elevations relative to the NAVD88 vertical datum were computed using National Geodetic Survey Geoid12b offsets. Bathymetric data were merged with post-processed positioning data and spurious soundings were removed using a custom Graphical User Interface (GUI) programmed with the computer program MATLAB. The final point data from the survey vessel was projected in cartesian coordinates using the Universal Transverse Mercator Zone 4 North, meters coordinate system. 20200423 All available bathymetry data from the survey were compiled into a comma-delimited text file for distribution. 20210512 Point Point 895748 0.00000001 0.00000001 Decimal Degrees North American Datum of 1983, 2011 realization GRS_1980 6378137.0 298.257222101 North American Vertical Datum of 1988 0.001 meters Explicit elevation coordinate included with horizontal coordinates Attribute Table Table containing attribute information associated with the dataset. Producer defined Survey_Date_Time The date and time of data collection in Greenwich Mean Time (GMT). Producer defined 2019-Jul-09 19:55:20.589 2019-Jul-12 20:27:05.249 Date and time in yyyy-mmm-dd hh:mm:ss.fff format 0.001 Longitude Longitude coordinate of data point relative to the North American Datum of 1983, 2011 realization Producer defined -160.8639194 -160.7666941 Decimal degrees 0.0000001 Latitude Latitude coordinate of data point relative to the North American Datum of 1983, 2011 realization Producer defined 63.84667372 63.88136471 Decimal degrees 0.0000001 Easting_m Easting coordinate of data point relative to the North American Datum of 1983, 2011 realization, projected to the Universal Transverse Mercator, Zone 4. Producer defined 408372.883 413201.097 Meters 0.001 Northing_m Northing coordinate of data point relative to the North American Datum of 1983, 2011 realization, projected to the Universal Transverse Mercator, Zone 4. Producer defined 7081260.852 7085018.336 Meters 0.001 Ellip_Ht_m Height in meters of data point with reference to the reference ellipsoid. Producer defined 0.324 9.366 Meters 0.001 Ortho_Ht_m Height in meters of data point with reference to the North American Vertical Datum of 1988. Producer defined -7.416 1.598 Meters 0.001 U.S. Geological Survey - ScienceBase Mailing and Physical

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Denver CO 80225 1-888-275-8747 sciencebase@usgs.gov Bathymetry data are available as a comma-delimited text file (unk19_july_bathymetry.csv), along with associated metadata. 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. comma-delimited text Matlab 8.6.0.958874 text comma-delimited text file 19.1 https://www.sciencebase.gov/catalog/file/get/60c24fbad34e86b9389559b8 https://doi.org/10.5066/P9238F8K Data can be downloaded using the Network_Resource_Name links. The first link is a direct link to download the zipped file of data and metadata. The second link points to a landing page for the entire data release. None. 20210719 U.S. Geological Survey, Pacific Coastal and Marine Science Center PCMSC Science Data Coordinator mailing and physical

2885 Mission Street

Santa Cruz CA 95060 831-427-4747 pcmsc_data@usgs.gov Content Standard for Digital Geospatial Metadata FGDC-STD-001-1998