Nearshore bathymetry data from the Unalakleet River mouth, Alaska, 2019

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Metadata:

Identification_Information
Data_Quality_Information
Spatial_Data_Organization_Information
Spatial_Reference_Information
Entity_and_Attribute_Information
Distribution_Information
Metadata_Reference_Information

Identification_Information:

Citation:

Citation_Information:

Originator: Alexander G. Snyder
Originator: Cordell D. Johnson
Originator: Ann E. Gibbs
Originator: Li H. Erikson
Publication_Date: 20210719
Title:

Nearshore bathymetry data from the Unalakleet River mouth, Alaska, 2019

Geospatial_Data_Presentation_Form: comma-delimited text
Series_Information:

Series_Name: data release
Issue_Identification: DOI:10.5066/P9238F8K

Publication_Information:

Publication_Place:

Pacific Coastal and Marine Science Center, Santa Cruz, California

Publisher: U.S. Geological Survey

Online_Linkage: https://doi.org/10.5066/P9238F8K
Online_Linkage:

https://www.sciencebase.gov/catalog/item/60c24fbad34e86b9389559b8

Description:

Abstract:

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.

Purpose:

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.

Supplemental_Information:

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.

Time_Period_of_Content:

Time_Period_Information:

Range_of_Dates/Times:

Beginning_Date: 20190709
Ending_Date: 20190712

Currentness_Reference: ground condition at time data were collected

Status:

Progress: Complete
Maintenance_and_Update_Frequency: None planned

Spatial_Domain:

Bounding_Coordinates:

West_Bounding_Coordinate: -160.863919
East_Bounding_Coordinate: -160.766694
North_Bounding_Coordinate: 63.881365
South_Bounding_Coordinate: 63.846674

Keywords:

Theme:

Theme_Keyword_Thesaurus: ISO 19115 Topic Category
Theme_Keyword: elevation

Theme:

Theme_Keyword_Thesaurus: Data Categories for Marine Planning
Theme_Keyword: Bathymetry and Elevation

Theme:

Theme_Keyword_Thesaurus: USGS Thesaurus
Theme_Keyword: bathymetry
Theme_Keyword: bathymetry measurement
Theme_Keyword: GPS measurement

Theme:

Theme_Keyword_Thesaurus: Marine Realms Information Bank (MRIB) keywords
Theme_Keyword: single-beam echo sounder
Theme_Keyword: Global Positioning System (GPS) observations

Theme:

Theme_Keyword_Thesaurus: None
Theme_Keyword: U.S. Geological Survey
Theme_Keyword: USGS
Theme_Keyword: Coastal and Marine Hazards and Resources Program
Theme_Keyword: CMHRP
Theme_Keyword: Pacific Coastal and Marine Science Center
Theme_Keyword: PCMSC

Theme:

Theme_Keyword_Thesaurus: USGS Metadata Identifier
Theme_Keyword: USGS:60c24fbad34e86b9389559b8

Place:

Place_Keyword_Thesaurus: Geographic Names Information System (GNIS)
Place_Keyword: Norton Sound
Place_Keyword: Pacific Ocean
Place_Keyword: Unalakleet
Place_Keyword: City of Unalakleet
Place_Keyword: Unalakleet River
Place_Keyword: State of Alaska
Place_Keyword: Nome Census Area

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 as the originator of the dataset and in products derived from these data. This information is not intended for navigation purposes.

Point_of_Contact:

Contact_Information:

Contact_Organization_Primary:

Contact_Organization:

U.S. Geological Survey, Pacific Coastal and Marine Science Center

Contact_Person: PCMSC Science Data Coordinator

Contact_Address:

Address_Type: mailing and physical
Address: 2885 Mission Street
City: Santa Cruz
State_or_Province: CA
Postal_Code: 95060

Contact_Voice_Telephone: 831-427-4747
Contact_Electronic_Mail_Address: pcmsc_data@usgs.gov

Native_Data_Set_Environment: MATLAB Version: 8.6.6.958874 (R2015b)
Cross_Reference:

Citation_Information:

Originator: International Hydrographic Organization (IHO)
Publication_Date: 2008
Title: IHO standards for hydrographic surveys (6th ed.)
Online_Linkage:

https://iho.int/uploads/user/pubs/Drafts/S-44_Edition_6.0.0-Final.pdf

Data_Quality_Information:

Attribute_Accuracy:

Attribute_Accuracy_Report: No formal attribute accuracy tests were conducted.

Logical_Consistency_Report: All data falls within expected ranges.
Completeness_Report:

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.

Positional_Accuracy:

Horizontal_Positional_Accuracy:

Horizontal_Positional_Accuracy_Report:

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.

Vertical_Positional_Accuracy:

Vertical_Positional_Accuracy_Report:

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.

Lineage:

Process_Step:

Process_Description:

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.

Process_Date: 20190712

Process_Step:

Process_Description:

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.

Process_Date: 20200423

Process_Step:

Process_Description:

All available bathymetry data from the survey were compiled into a comma-delimited text file for distribution.

Process_Date: 20210512

Spatial_Data_Organization_Information:

Direct_Spatial_Reference_Method: Point
Point_and_Vector_Object_Information:

SDTS_Terms_Description:

SDTS_Point_and_Vector_Object_Type: Point
Point_and_Vector_Object_Count: 895748

Spatial_Reference_Information:

Horizontal_Coordinate_System_Definition:

Geographic:

Latitude_Resolution: 0.00000001
Longitude_Resolution: 0.00000001
Geographic_Coordinate_Units: Decimal Degrees

Geodetic_Model:

Horizontal_Datum_Name: North American Datum of 1983, 2011 realization
Ellipsoid_Name: GRS_1980
Semi-major_Axis: 6378137.0
Denominator_of_Flattening_Ratio: 298.257222101

Vertical_Coordinate_System_Definition:

Altitude_System_Definition:

Altitude_Datum_Name: North American Vertical Datum of 1988
Altitude_Resolution: 0.001
Altitude_Distance_Units: meters
Altitude_Encoding_Method:

Explicit elevation coordinate included with horizontal coordinates

Entity_and_Attribute_Information:

Detailed_Description:

Entity_Type:

Entity_Type_Label: Attribute Table
Entity_Type_Definition:

Table containing attribute information associated with the dataset.

Entity_Type_Definition_Source: Producer defined

Attribute:

Attribute_Label: Survey_Date_Time
Attribute_Definition:

The date and time of data collection in Greenwich Mean Time (GMT).