Nearshore bathymetry of Humboldt Bay North Spit and South Spit, California

Frequently anticipated questions:

• What does this data set describe?
  1. How might this data set be cited?
  2. What geographic area does the data set cover?
  3. What does it look like?
  4. Does the data set describe conditions during a particular time period?
  5. What is the general form of this data set?
  6. How does the data set represent geographic features?
  7. How does the data set describe geographic features?
• Who produced the data set?
  1. Who are the originators of the data set?
  2. Who also contributed to the data set?
  3. To whom should users address questions about the data?
• Why was the data set created?
• How was the data set created?
  1. From what previous works were the data drawn?
  2. How were the data generated, processed, and modified?
  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?
  3. How accurate are the heights or depths?
  4. Where are the gaps in the data? What is missing?
  5. How consistent are the relationships among the data, including topology?
• How can someone get a copy of the data set?
  1. Are there legal restrictions on access or use of the data?
  2. Who distributes the data?
  3. What's the catalog number I need to order this data set?
  4. What legal disclaimers am I supposed to read?
  5. How can I download or order the data?
• Who wrote the metadata?

What does this data set describe?

1. How might this data set be cited?
   Stevens, Andrew W., Logan, Josh B., Currie, Jackson E., Elfers, Timothy C., and Parker, Kai A., 20260604, Nearshore bathymetry of Humboldt Bay North Spit and South Spit, California: data release DOI:10.5066/P1SNSQB9, U.S. Geological Survey, Pacific Coastal and Marine Science Center, Santa Cruz, California.

   Online Links:

   • https://doi.org/10.5066/P1SNSQB9

   This is part of the following larger work.
   Stevens, Andrew W., Logan, Josh B., Currie, Jackson E., Elfers, Timothy, and Parker, Kai A., 2026, Beach topography and nearshore bathymetry of Humboldt Bay North and South Spits, California: data release DOI:10.5066/P1SNSQB9, U.S. Geological Survey, Pacific Coastal and Marine Science Center, Santa Cruz, CA.

   Online Links:

   • https://doi.org/10.5066/P1SNSQB9

   Other_Citation_Details:

   Suggested Citation: Stevens, A.W., Logan, J.B., Currie, J.E., Elfers, T.C., and Parker, K.A., 2026, Beach topography and nearshore bathymetry of Humboldt Bay North and South Spits, California: U.S. Geological Survey data release, https://doi.org/10.5066/P1SNSQB9.

2. What geographic area does the data set cover?

   West_Bounding_Coordinate: -124.2866575
   East_Bounding_Coordinate: -124.1677396
   North_Bounding_Coordinate: 40.8666435
   South_Bounding_Coordinate: 40.7000867
   

3. What does it look like?
4. Does the data set describe conditions during a particular time period?

   Beginning_Date: 29-Apr-2025

   Ending_Date: 17-Sep-2025

   Currentness_Reference:

   Ground condition at time data were collected

5. What is the general form of this data set?

   Geospatial_Data_Presentation_Form: comma-delimited text
   

6. How does the data set represent geographic features?
   1. How are geographic features stored in the data set?
      This is a Point data set. It contains the following vector data types (SDTS terminology):
      • Point (808183)
   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 0.0000001. Longitudes are given to the nearest 0.0000001. Latitude and longitude values are specified in Decimal degrees. The horizontal datum used is North American Datum of 1983.
      The ellipsoid used is GRS_1980.
      The semi-major axis of the ellipsoid used is 6378137.0.
      The flattening of the ellipsoid used is 1/298.257222101.
      

      Vertical_Coordinate_System_Definition:

      Altitude_System_Definition:

      Altitude_Datum_Name: North American Vertical Datum of 1988
      Altitude_Resolution: 0.01
      Altitude_Distance_Units: meters
      Altitude_Encoding_Method:

      Explicit elevation coordinate included with horizontal coordinates

7. How does the data set describe geographic features?

   hb[yy]_[mmm]_bathy.csv

   Table containing attribute information associated with the bathymetry dataset, where [yy]_[mmm] in the file name is the year and month in which the data were collected. (Source: Producer defined)

   line_number

   Numeric code identifying the number of the survey line. Data that were not collected along a survey line are labeled "None". (Source: Producer defined)

   Range of values
   Minimum:	001
   Maximum:	104

   datetime_utc

   The date and time of data collection in Coordinated Universal Time (UTC). (Source: Producer defined)

   Range of values
   Minimum:	2025-Apr-29 18:27:28.627
   Maximum:	2025-Sep-17 20:21:53.164
   Units:	date and time in yyyy-mmm-dd HH:MM:SS.FFF format

   longitude

   Longitude coordinate of data point relative to the North American Datum of 1983 (EPSG: 4269) (Source: Producer defined)

   Range of values
   Minimum:	-124.2866575
   Maximum:	-124.1677396
   Units:	Decimal degrees

   latitude

   Latitude coordinate of data point relative to the North American Datum of 1983 (EPSG: 4269) (Source: Producer defined)

   Range of values
   Minimum:	40.7000867
   Maximum:	40.8666435
   Units:	Decimal degrees

   easting_m

   East coordinate of data point relative to the North American Datum of 1983, projected in the Universal Transverse Mercator Zone 10N, meters, coordinate system (EPSG: 6339) (Source: Producer defined)

   Range of values
   Minimum:	391307.19
   Maximum:	401586.93
   Units:	meters

   northing_m

   North coordinate of data point relative to the North American Datum of 1983, projected in the Universal Transverse Mercator Zone 10N, meters, coordinate system (EPSG: 6339) (Source: Producer defined)

   Range of values
   Minimum:	4506247.93
   Maximum:	4524622.45
   Units:	meters

   distance_m

   Distance from reference point along planned survey line. Distances are relative to an arbitrary reference point. Depending on the orientation of the target line and position of the reference point, the along-line distance can be positive or negative in any direction. NaN=not a number, because the data were not collected along a pre-defined survey line. (Source: Producer defined)

   Range of values
   Minimum:	-244.27
   Maximum:	1930.91
   Units:	meters

   offline_m

   Horizontal distance from planned survey line. Depending on the orientation of the target line and position of the reference point, the offline distance can be positive or negative in any direction. NaN=not a number, because the data were not collected along a pre-defined survey line. (Source: Producer defined)

   Range of values
   Minimum:	-20.00
   Maximum:	19.99
   Units:	meters

   ellipsoid_ht_m

   Height in meters of data point with reference to the reference ellipsoid (Source: Producer defined)

   Range of values
   Minimum:	-54.35
   Maximum:	-30.25
   Units:	meters

   ortho_ht_m

   Height in meters relative to the NAVD88 vertical datum, computed assuming National Geodetic Survey Geoid18. (Source: Producer defined)

   Range of values
   Minimum:	-23.53
   Maximum:	0.62
   Units:	meters

   Entity_and_Attribute_Overview:

   [MA3.1]This dataset contains one comma separated values (csv) bathymetry data file for each field activity. Data files are named hb[yy]_[mmm]_bathy.csv, in which [yy]_[mmm] indicate the year and month of the survey. The first line of the csv file is a header line.

   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)
   • Andrew W. Stevens
   • Josh B. Logan
   • Jackson E. Currie
   • Timothy C. Elfers
   • Kai A. Parker
2. Who also contributed to the data set?
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)

   pcmsc_data@usgs.gov

Why was the data set created?

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: 2025 (process 1 of 4)

   Geodetic control for the project was established using simultaneous static GNSS network surveys on four benchmarks installed near the study area. Static GNSS occupations were conducted on these benchmarks during February, April, and May 2025. Observation data from each session were processed using the National Geodetic Survey’s Online Positioning User Service (OPUS) Projects. All static observations used in the network adjustment met USGS Level I quality standards for single-base OPUS-S surveys. The resulting geodetic control is aligned to the National Spatial Reference System (NSRS) through the North American Datum of 1983, National Adjustment of 2011 (NAD83(2011)), at epoch 2010.00. Elevations are referenced to the North American Vertical Datum of 1988 (NAVD88), with orthometric heights computed using NGS GEOID18.

   Date: 17-Sep-2025 (process 2 of 4)

   Bathymetric data were acquired using single-beam sonar systems and global navigation satellite systems (GNSS) receivers mounted on personal watercraft (PWC). Depths from the echosounders were computed using sound velocity profiles measured using a CTD during the survey. Positioning of the survey vessels was determined at 10 Hz using dual frequency GNSS receivers. Output from the GNSS receivers and sonar systems were combined in real time by a computer running HYPACK hydrographic survey software. Navigation information was displayed on a video monitor, allowing vessel operators to navigate along planned survey lines.

   Date: 23-Sep-2025 (process 3 of 4)

   Precise positioning of the bathymetric platforms was achieved with a single GNSS base station transmitting differential corrections in real time via UHF radio modem at 1-Hz intervals. Positioning data from the bathymetric survey platforms were later post-processed using Waypoint Grafnav to apply differential corrections from the GNSS base station. These post-processed positions superseded those that were recorded in the field. Orthometric elevations relative to the NAVD88 vertical datum were computed using the National Geodetic Survey Geoid18 geoid model. 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 are projected in cartesian coordinates using the Universal Transverse Mercator (UTM), Zone 10N meters coordinate system.

   Date: 25-Sep-2025 (process 4 of 4)

   All available bathymetric data from the surveys were compiled into a comma-delimited text files (one file for each survey) for distribution

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?
   No formal attribute accuracy tests were conducted.
2. How accurate are the geographic locations?
   Manufacturer reported accuracy for the differentially corrected horizontal positions for both bathymetric and topographic measurements is 0.8 cm + 0.5 ppm, where ppm refers to baseline distances between GNSS rovers and base stations in parts per million. Mean and maximum baselines from the GNSS base station during the survey were 3.1 km and 6.3 km, respectively suggesting a mean and maximum horizontal accuracy of bathymetric and topographic positions to be between 0.67 centimeters (cm) and 0.82 cm relative to the base station coordinate. Uncertainty in the horizontal positions associated with pitch and roll of the survey vessels during data collection is unknown.
3. How accurate are the heights or depths?
   Uncertainty in the vertical positions of the GNSS measurements was estimated based on the accuracy of the Trimble GNSS rovers used in the survey. Manufacturer reported accuracy for the differentially corrected vertical positions for the GNSS rover trajectories is 1.5 cm + 1 ppm. The maximum baseline from the GNSS base station during the survey was 6.3 km, suggesting a minimum vertical accuracy of 2.76 cm relative to the base station coordinate. The bathymetric measurements include additional sources of vertical uncertainty associated with the CEEHydrosystems CEESCOPE single beam echosounder systems used in this survey. The manufacturer of the single beam echosounders reports a vertical uncertainty of 1 cm + 1 percent of water depth. Based on a mean (7 m) and maximum water depth (23.7 m) measured during the survey, the mean and maximum vertical uncertainty for the bathymetric soundings is estimated to be 8 and 24 cm, respectively. Combining the uncertainty related to the GNSS positions and bathymetric soundings in quadrature yields a total mean and max vertical uncertainty of 8.5 and 24.2 cm respectively for the final bathymetric elevations. Uncertainty in the vertical positions associated with pitch and roll of the survey vessels is unknown.
4. Where are the gaps in the data? What is missing?
   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.
5. How consistent are the relationships among the observations, including topology?
   No formal logical accuracy tests were conducted.

How can someone get a copy of the data set?

1. Who distributes the data set? (Distributor 1 of 1)
   
   U.S. Geological Survey - Coastal and Marine Geoscience Data System

   2885 Mission Street

   Santa Cruz, CA
   

   USA

   831-427-4747 (voice)

   pcmsc_data@usgs.gov
2. What's the catalog number I need to order this data set? Bathymetric data from each survey are available as separate comma-delimited text files, along with associated FGDC-compliant metadata.
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?
   • Availability in digital form:

     Data format:	comma-delimited text file in format comma-delimited text (version MATLAB Version: 25.2.0.2998904 (R2025b)) Size: 77.8
     Network links:	https://doi.org/10.5066/P1SNSQB9

   • Cost to order the data: None

Who wrote the metadata?

Dates:

Last modified: 04-Jun-2026

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)

pcmsc_data@usgs.gov

Metadata standard:

Content Standard for Digital Geospatial Metadata (FGDC-STD-001-1998)