Digital elevation models (DEMs) of the beach and nearshore in Santa Cruz, 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?
   Snyder, Alexander G., Stevens, Andrew W., Logan, Joshua B., Hoover, Daniel J., and Barnard, Patrick L., 20241219, Digital elevation models (DEMs) of the beach and nearshore in Santa Cruz, California: data release DOI: 10.5066/P134BC6W, U.S. Geological Survey, Pacific Coastal and Marine Science Center, Santa Cruz, California.

   Online Links:

   • https://doi.org/10.5066/P134BC6W

   Other_Citation_Details:

   Suggested Citation: Snyder, A.G., Stevens, A.W., Logan, J.B., Hoover, D.J., and Barnard, P.L., 2024, Digital elevation models (DEMs) of the beach and nearshore in Santa Cruz, California: U.S. Geological Survey data release, https://doi.org/10.5066/P134BC6W.

2. What geographic area does the data set cover?

   West_Bounding_Coordinate: -122.025848
   East_Bounding_Coordinate: -121.992327
   North_Bounding_Coordinate: 36.965868
   South_Bounding_Coordinate: 36.951706
   

3. What does it look like?

   AllGridsTSP_3_5m_241112.png (png)

   Maps of each digital elevation model included in this data release, with the -3.5 m (NAVD88) contour displayed to illustrate some of the change in bathymetry.

4. Does the data set describe conditions during a particular time period?

   Calendar_Date: 20-Oct-2014

   Currentness_Reference:

   ground condition at time data were collected

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

   Geospatial_Data_Presentation_Form: GeoTIFF
   

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 770 x 1484, type Pixel
   2. What coordinate system is used to represent geographic features?
      

      Grid_Coordinate_System_Name: Universal Transverse Mercator
      Universal_Transverse_Mercator:

      UTM_Zone_Number: 10
      Transverse_Mercator:

      Scale_Factor_at_Central_Meridian: 0.9996
      Longitude_of_Central_Meridian: -123.0
      Latitude_of_Projection_Origin: 0.0
      False_Easting: 500000.0
      False_Northing: 0.0
      

      Planar coordinates are encoded using coordinate pair
      Abscissae (x-coordinates) are specified to the nearest 2
      Ordinates (y-coordinates) are specified to the nearest 2
      Planar coordinates are specified in Meter
      The horizontal datum used is D_North_American_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?

   Attribute Table

   Table containing attribute information associated with the dataset (Source: Producer defined)

   Elevation (NAVD88 GEOID12A)

   Elevation relative to the North American vertical datum of 1988 (NAVD88 GEOID12A) (Source: Producer Defined)

   Range of values
   Minimum:	-10.53
   Maximum:	9.71
   Units:	meters
   Resolution:	0.01

   Entity_and_Attribute_Overview:

   The DEM is presented as a 32-bit floating point GeoTIFF where pixels represent elevation in meters relative to NAVD88 and the no-data value is -9999. The horizontal projection is NAD83(2011) UTM Zone 10N.

   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)
   • Alexander G. Snyder
   • Andrew W. Stevens
   • Joshua B. Logan
   • Daniel J. Hoover
   • Patrick L. Barnard
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: 08-Mar-2024 (process 1 of 5)

   Bathymetric data were collected using single-beam sonar systems and global navigation satellite systems (GNSS) receivers mounted on personal watercraft (PWC). The sonar systems consisted of an Odom Echotrac CV-100 or CEE Hydrosystems CeeScope single-beam echosounder and 200 kHz transducer with a 9-degree beam angle. Depths from the echosounders were computed using sound velocity profiles measured using a YSI CastAway CTD during the survey. Positioning of the survey vessels was determined at 10 Hz using survey-grade GNSS receivers. Output from the GNSS receivers and sonar systems were combined in real time on the PWC by a computer running HYPACK hydrographic survey software. Navigation information was displayed on a video monitor, allowing PWC operators to navigate along survey lines at speeds of 2 to 3 m/s.

   Date: 08-Mar-2024 (process 2 of 5)

   Topographic profiles were collected on foot with GNSS receivers mounted on backpacks. Prior to data collection, vertical distances between the GNSS antennas and the ground were measured using a tape measure. Hand-held data collectors were used to log raw data and display navigational information allowing surveyors to navigate cross-shore survey lines spaced at 50- to 100-m intervals along the beach. Profiles were surveyed from the landward edge of the study area (either the base of a bluff, engineering structure, or just landward of the primary dune) over the beach foreshore, to wading depth on the same series of transects as nearshore bathymetric surveys that were conducted during the same time period.

   Date: 10-Jun-2024 (process 3 of 5)

   Positions of the survey platforms were post-processed using a single-base station and differential post-processing. Positioning data from the GNSS receivers on the PWCs were post-processed using Waypoint Grafnav to apply differential corrections from a GNSS base station with known horizontal and vertical coordinates relative to the North American Datum of 1983. Orthometric elevations relative to the NAVD88 vertical datum were computed using National Geodetic Survey GEOID12A 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 PWCs are projected in Cartesian coordinates using the UTM Zone 10 North, meters coordinate system.

   Date: 10-Jun-2024 (process 4 of 5)

   Topographic survey data from the backpack mounted GNSS receivers that were collected in autonomous mode were post-processed to apply differential corrections from a GNSS base station with known horizontal and vertical coordinates relative to the North American Datum of 1983. Post-processing of raw GNSS data was performed with Trimble Business Center. Orthometric elevations relative to the NAVD88 vertical datum were computed using National Geodetic Survey GEOID12A offsets. The final point data from the topographic surveyors are also projected in Cartesian coordinates using the UTM Zone 10 North, meters coordinate system.

   Date: 08-Sep-2024 (process 5 of 5)

   Comparisons were performed to ensure internal consistency between the survey platforms. DEMs were produced by linear interpolation of all available elevation point data with the computer program MATLAB. The DEM generation methods are described in more detail in East and other, 2018. Data were exported in GeoTIFF raster format for distribution.

3. What similar or related data should the user be aware of?
   East, Amy E., Stevens, Andrew W., Ritchie, Andrew C., Barnard, Patrick L., Campbell-Swarzenski, Pamela, Collins, Brian D., and Conaway, Christopher H., 2018, A regime shift in sediment export from a coastal watershed during a record wet winter, California: Implications for landscape response to hydroclimatic extremes.

   Online Links:

   • https://doi.org/10.1002/esp.4415

   International Hydrographic Organization (IHO), 2008, IHO Standards for Hydrographic surveys (5th ed.).

   Online Links:

   • https://iho.int/uploads/user/pubs/standards/s-44/S-44_Edition_6.1.0.pdf

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?
   Digital elevation models (DEMs) were created by interpolating between elevation measurements as much as 100 meters apart, for this reason we cannot evaluate the accuracy of each point in a DEM, only the original data from which it is generated. Manufacturer-reported accuracy for the differentially corrected horizontal positions for the GNSS receivers used to collect the topographic and bathymetric measurements is 0.8 cm + 0.5 ppm. Baselines from the GNSS base station were typically less than 5 km, suggesting a horizontal accuracy of survey-vessel positions to be 0.825 cm relative to the base station. The combined horizontal uncertainty from the base station coordinate solutions and rover trajectories is between 1.5 cm and 7 cm, with a mean horizontal uncertainty of 3 cm. Uncertainty in the horizontal positions associated with pitch and roll of the survey vessels and variable surveyor posture during the backpack surveys is unknown.
3. How accurate are the heights or depths?
   Digital elevation models (DEMs) were created by interpolating between elevation measurements as much as 200 meters apart, for this reason we cannot evaluate the accuracy of each point in a DEM, only the original data from which it is generated. An average estimated vertical accuracy of 3 cm for the topographic GNSS backpack was estimated by using the manufacturer reported vertical accuracy of 1.5 cm + 1 ppm for differentially corrected kinematic data. Uncertainty in the bathymetry data is related to the precision of the GNSS positioning and single-beam echosounders as well as unmeasured variability in the speed of sound used to compute depths from bathymetric soundings. 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 of the bathymetry data is calculated using the constant- and depth-dependent factors summed in quadrature (International Hydrographic Organization (IHO), 2008). The average vertical uncertainty in bathymetry data is estimated to be 9 cm.
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?
   All data falls within expected ranges.

How can someone get a copy of the data set?

1. Who distributes the data set? (Distributor 1 of 1)
   
   U.S. Geological Survey - CMGDS

   2885 Mission Street

   Santa Cruz, CA
   

   1-831-427-4747 (voice)

   pcmsc_data@usgs.gov
2. What's the catalog number I need to order this data set? DEM grids are available in GeoTIFF format with names that specifies the survey area (Santa Cruz), year, month, and grid size (‘SCYY_MMM_2m.tiff’). For example, a DEM generated from survey data collected in March 2024 with a 2-meter grid size, would be named ‘SC24_Mar_2m.tiff’. The file size of each individual GeoTIFF file is 4.47 MB. FGDC-compliant metadata file is also included.
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:	Each GeoTIFF file contains a 2-meter resolution digital elevation model of the beach and nearshore adjacent to Santa Cruz, CA. in format GeoTIFF (version Matlab Version: 24.1.0.2568132 (R2024a)) Size: 88
     Network links:	https://doi.org/10.5066/P134BC6W

   • Cost to order the data: None.

5. What hardware or software do I need in order to use the data set?
   These data can be viewed with any geographic information software.

Who wrote the metadata?

Dates:

Last modified: 19-Dec-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)

pcmsc_data@usgs.gov

Metadata standard:

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