Input Data Boundary Outlines for DEMs of the North-Central California Coast (DEM_source_data.shp)

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Frequently anticipated questions:


What does this data set describe?

Title:
Input Data Boundary Outlines for DEMs of the North-Central California Coast (DEM_source_data.shp)
Abstract:
A GIS polygon shapefile outlining the boundaries of the native input datasets used to construct a seamless, 2-meter resolution digital elevation model (DEM) was constructed for the open-coast region of the San Francisco Bay Area (outside of the Golden Gate Bridge), extending from Half Moon Bay to Bodega Head along the North-central California coastline. The goal was to integrate the most recent high-resolution bathymetric and topographic datasets available (for example, Light Detection and Ranging (lidar) topography, multibeam and single-beam sonar bathymetry) into a seamless surface model extending offshore at least 3 nautical miles and inland beyond the +20 m elevation contour.
Supplemental_Information:
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 dataset in nonproprietary form, as well as in ArcInfo format, this metadata file may include some ArcInfo-specific terminology.
  1. How might this data set be cited?
    U.S. Geological Survey (USGS), Pacific Coastal and Marine Science Center (PCMSC), Santa Cruz, CA., 2012, Input Data Boundary Outlines for DEMs of the North-Central California Coast (DEM_source_data.shp):.

    This is part of the following larger work.

    U.S. Geological Survey (USGS), Pacific Coastal and Marine Science Center (PCMSC), Santa Cruz, CA., 2012, A Seamless, High-Resolution Digital Elevation Model (DEM) of the North-Central California Coast: U.S. Geological Survey Data Series Data Series 684.

    Online Links:

  2. What geographic area does the data set cover?
    West_Bounding_Coordinate: -123.158145
    East_Bounding_Coordinate: -122.393965
    North_Bounding_Coordinate: 38.352385
    South_Bounding_Coordinate: 37.407828
  3. What does it look like?
  4. Does the data set describe conditions during a particular time period?
    Beginning_Date: 1984
    Ending_Date: 2011
    Currentness_Reference:
    topography at time underlying dataset was collected (See Source Information)
  5. What is the general form of this data set?
    Geospatial_Data_Presentation_Form: raster digital data
  6. How does the data set represent geographic features?
    1. How are geographic features stored in the data set?
      This is a Vector data set. It contains the following vector data types (SDTS terminology):
      • G-polygon (1023)
    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: 0.999600
      Longitude_of_Central_Meridian: -123
      Latitude_of_Projection_Origin: 0.000000
      False_Easting: 500000.000000
      False_Northing: 0.000000
      Planar coordinates are encoded using coordinate pair
      Abscissae (x-coordinates) are specified to the nearest 0.000001
      Ordinates (y-coordinates) are specified to the nearest 0.000001
      Planar coordinates are specified in meters
      The horizontal datum used is North American Datum of 1983.
      The ellipsoid used is Geodetic Reference System 80.
      The semi-major axis of the ellipsoid used is 6378137.000000.
      The flattening of the ellipsoid used is 1/298.257222.
  7. How does the data set describe geographic features?
    Entity_and_Attribute_Overview:
     Polygon attributes
          Data_type  - type of data (bathymetry, lidar, etc.)
          Date - date of data collection
       Agency -  agency that collected the data or commissioned its collection
          Native_res - native horizontal resolution of the source data
          Survey_ID - survey ID used in website or data report
    
    Entity_and_Attribute_Detail_Citation: none

Who produced the data set?

  1. Who are the originators of the data set? (may include formal authors, digital compilers, and editors)
    • U.S. Geological Survey (USGS), Pacific Coastal and Marine Science Center (PCMSC), Santa Cruz, CA.
  2. Who also contributed to the data set?
    California State University, Monterey Bay (CSUMB) and Fugro Pelagos, Inc., for California State Waters Mapping Project (CSWMP) from Pat Iampietro; Pillar Point Harbor from Anne Sturm (U.S. Army Corps of Engineers); National Geophysical Data Center (NGDC); National Oceanic and Atmospheric Administration (NOAA); Marin County from Brian Quinn (County of Marin GIS Division of Community Development Agency); Bolinas Lagoon from Matt Brennan (ESA-PWA); Carignan, K.S., Taylor, L.A., Eakins, B.W., Caldwell, R.J., Friday, D.Z., Grothe, P.R., and Lim, E., 2011, Digital elevation models of central California and San Francisco Bay: Procedures, data sources and analysis: NOAA Technical Memorandum NESDIS NGDC-52, 49 p. and datasets, available at: http://www.ngdc.noaa.gov/dem/squareCellGrid/download/741
  3. To whom should users address questions about the data?
    Patrick L. Barnard
    U.S. Geological Survey (USGS) Coastal and Marine Geology (CMG)
    Reserach Geologist
    USGS, 400 Natural Bridges Drive
    Santa Cruz, CA
    USA

    (831) 460-7556 (voice)
    (831) 427-4748 (FAX)
    pbarnard@usgs.gov

Why was the data set created?

This DEM data set was constructed to provide critical model boundary conditions (bathymetry and topography) necessary to predict the impacts of severe winter storms and sea level rise along this stretch of coast, using the Coastal Storm Modeling System (CoSMoS). This process based modeling system was first applied along the coast of Southern California (Barnard and others, 2009). CoSMoS can be run in real-time or with prescribed scenarios, incorporating atmospheric forcing information (wind and pressure fields) with a suite of state-of-the-art physical process models (WaveWatch3, SWAN, XBeach, Delft3D) to enable detailed prediction of water levels, run-up, wave heights, and currents, ultimately predicting the spatial distribution of coastal flooding, inundation, erosion, and cliff failure. The DEM was constructed to define the general shape of the nearshore, beach and cliff surfaces as accurately as possible, with less emphasis on the detailed variations in elevation inland of the coast and on bathymetry inside harbors. As a result this DEM should not be used for navigation purposes.

How was the data set created?

  1. From what previous works were the data drawn?
    CSUMB (source 1 of 11)
    California State University, Monterey Bay, Unknown, Multibeam bathymetry.

    Online Links:

    Other_Citation_Details: contact: Pat Iampietro <pat_iampietro@csumb.edu>
    Type_of_Source_Media: digital data - raster grids or ascii xyz text files
    Source_Contribution: Provided multibeam bathymetry for entire offshore study area.
    USGS (source 2 of 11)
    U.S. Geological Survey, lidar acquired by Terrapoint, Unknown, ARRA-CA_SanFranCoast_2010 lidar.

    Online Links:

    Other_Citation_Details: contact: Carol Ostergren <costergren@usgs.gov>
    Type_of_Source_Media: digital data - raster grids
    Source_Contribution:
    Provided topographic lidar data for coastal region (to approximately +10 m elevation contour) for stretch of coast from Point Reyes to Point San Pedro
    SFSU (source 3 of 11)
    San Francisco State University, lidar acquired by Earth Eye, Unknown, Golden Gate Lidar Project.

    Other_Citation_Details: contact: Ellen Hines <ehines@sfsu.edu>
    Type_of_Source_Media: digital data - raster grids or ascii xyz text files
    Source_Contribution:
    Provided topographic lidar data for Marin County, San Francisco County, and portions of San Mateo and Sonoma counties.
    OPC (source 4 of 11)
    California State Ocean Protection Council, Unknown, 2010 Coastal CA Lidar, Delivery Area 3.

    Other_Citation_Details: contact: Sheila Semans <ssemans@scc.ca.gov>
    Type_of_Source_Media: digital data - raster grids
    Source_Contribution:
    Provided topographic lidar data in the vicinity of Bodega Bay and the southernmost region of Half Moon Bay (areas not covered by USGS or SFSU 2010 lidar)
    NGDC (source 5 of 11)
    NOAA National Geophysical Data Center, 2011, Digital elevation models of central California and San Francisco Bay: Procedures, data sources and analysis. NOAA Technical Memorandum NESDIS NGDC-52.

    Online Links:

    Type_of_Source_Media: digital data - raster grids
    Source_Contribution: Provided data for entire study area.
    USACE (source 6 of 11)
    U.S. Army Corps of Engineers, Unknown, Pillar Point Harbor survey.

    Type_of_Source_Media: digital data - terrain dataset
    Source_Contribution: Provided bathy/topo DEM of Pillar Point Harbor
    USGS (source 7 of 11)
    U.S. Geological Survey, 2008, Interferometric Sidescan Bathymetry, Sediment and Foraminiferal Analyses; a New Look at Tomales Bay, California.

    Other_Citation_Details: USGS OFR 2008-1237
    Type_of_Source_Media: digital data - raster grids
    Source_Contribution: Provided bathymetry data for Tomales Bay
    none (source 8 of 11)
    GIS Division of Community Development Agency County of Marin, unknown, Marin County Terrain Dataset.

    Other_Citation_Details: contact: Brian Quinn <BQuinn@co.marin.ca.us>
    Type_of_Source_Media: digital data - raster terrain datasets
    Source_Contribution: Provided bathy/topo terrain dataset for Marin County
    ESA PWA (source 9 of 11)
    Environmental Science Associates, Philip Williams and Associates, Unknown, Bolinas Lagoon Bathymetry.

    Other_Citation_Details: contact: Matt Brennan <MBrennan@esassoc.com>
    Type_of_Source_Media: digital data - raster grids
    Source_Contribution: Provided bathymetry for Bolinas Lagoon
    USGS (source 10 of 11)
    U.S. Geologial Survey, Unknown, O-12-09-CA.

    Online Links:

    Other_Citation_Details: contact: Dan Hoover <dhoover@usgs.gov>
    Type_of_Source_Media: digital data - TIN converted to a raster
    Source_Contribution: Provided data from Ocean Beach, San Francisco ATV/PWC survey
    USGS (source 11 of 11)
    U.S. Geologial Survey, 1991, Pollution Studies of Drakes Estero, and Abbotts Lagoon Point Reyes National Seashore, California, USA.

    Online Links:

    Type_of_Source_Media: map - bathymetry contours
    Source_Contribution: Provided bathymetry for Drakes Estero
  2. How were the data generated, processed, and modified?
    Date: 2011 (process 1 of 2)
    (Summary) Performed by Amy Foxgrover and Patrick Barnard: ArcGIS was the primary software used for DEM construction. For each individual DEM, the native datasets were mosaicked into a single grid to preserve the original surfaces as closely as possible. Prior to mosaicking, datasets were gridded and (or) resampled to 2 m resolution (if necessary), and their spatial extents modified according to the following guidelines: 1. Data sets of comparable quality (for example, overlapping multibeam data), collected over the same time period were not clipped. In these instances the overlapping regions were blended together using the "Blend" algorithm in the Mosaic to New Raster tool in Arc Toolbox. The exception to this is for topographic data along the shoreline. Multiple high-resolution aerial lidar surveys were collected along the shoreline in 2010. Since the nearshore is a very dynamic region that can be modified greatly by a single storm event, rather than blending multiple high-resolution datasets (which could produce unrealistic beach morphology), data from a single time period were selected for use. Where possible, we used data collected in the fall for nearshore elevations to minimize the potential of winter storm effects. 2. In overlapping regions where the quality of one dataset was clearly inferior to the other (for example, regional 10-m resolution DEMs overlapping with 2-m resolution lidar), the spatial extent of the inferior data set was clipped so there was minimal overlap, typically about ~20 m, with the superior dataset. The overlapping regions then were smoothed together using the Blend algorithm. This range of overlap was found to be the most efficient for ensuring a smooth transition between datasets while minimizing the use of lower quality data. The spatial extent of each dataset used is included as a GIS shapefile. In addition, the areas of overlap were typically well outside of the dynamic coastal zone, which was typically covered by a single lidar pass, so any blending should have minimal impact for this important region.
    Date: 2011 (process 2 of 2)
    (Detailed DEM Construction Procedures) Performed by Amy Foxgrover and Patrick Barnard:
    
    1. Divide study area into ~10 km alongshore segments
        A. Define DEM coverage area/polygon that extends ~10 km alongshore, from 3 nautical
           miles offshore inland beyond the +20 m topographic contour
        B. Ensure that adjacent DEM coverage areas overlap by ~250 m
    2. Acquire most recent or highest resolution data sets in DEM coverage areas
        A. Lidar
        B. Multibeam bathymetry
        C. Local high-resolution beach topography (usually ATV-acquired) and nearshore bathymetry
           (usually PWC-acquired).
    3. Fill gaps with older/lower resolution datasets
        A. Lower resolution DEMs - for example, NGDC's 10-m resolution tsunami inundation DEM,
           (Carignan and others, 2011) in Bodega Harbor
        B. Bathymetric data derived from single beam bathymetry - for example, 1980s survey in Drakes
           Estero and 1998 bathymetry in Bolinas Lagoon
    4. Convert all datasets into identical horizontal coordinate system, vertical datum, and grid resolution
        A. Horizontal coordinate system: UTM NAD83 Zone 10 North
        B. Vertical Datum: NAVD88
            I.   If different [usually Mean Lower Low Water (MLLW)], convert using local NOAA tide station information
                 [http://tidesandcurrents.noaa.gov/ (last accessed December 12, 2011)] based on survey metadata
        C. Grid resolution: 2 m
            I.   If already gridded at higher resolution(<2 m), resample to 2 m using bilinear interpolation
            II.  If already gridded at a lower resolution (> 2m), export as xyz file, reimport as xyz points, create TIN
                 (triangular irregular network), create 2-m grid from TIN using linear interpolation of the TIN triangles,
                 and clip to survey extent
            III. Ungridded:
                 a) Lower resolution surveys (for example, PWC-collected bathymetry): create TIN from points then
                    convert to 2-m grid using linear interpolation of the TIN triangles
    5. Clip datasets to DEM/coverage needs, if necessary
        A. Useful for data management and processing efficiency
        B. Necessary for very large data sets, such as county-wide lidar datasets (for example, Golden Gate Lidar Project data)
        C. Remove ocean water surfaces and offshore rocky outcrops/islands
            I.   Aerial topographic lidar from 2010 was provided as bare-earth hydro-flattened DEMs.  The breakline polygons provided
                 with aerial lidar data were used to generate 2-m resolution grids of water surfaces over the ocean or tidal embayments
                 where bathymetric data was to be inserted.  Use this grid to mask out water surfaces in the topographic DEM using the
                 Set Null tool in Arc Toolbox.
            II.  Hydro-flattened surfaces of small inland water bodies were retained in the final DEM.  Since these areas are of less
                 importance for this research, no attempt was made to obtain bathymetric depths for these inland ponds or lakes (for example,
                 Lake Merced in San Francisco). Hydro-flattened features that were retained in the final DEM are provided in shapefile format
                 at the end of this report.
            III. Extract small islands and rocky outcrops from topographic lidar datasets using breaklines provided.  These features are
                 not included in the nearshore interpolation, but are incorporated into the final DEM in step 8.
    6. Manage overlapping datasets
        A. Data sets were allowed to overlap extensively only if they are from the same time period, of comparable quality, and not within
           the dynamic nearshore region, otherwise allow only minimal (~10-30 m) overlap to ensure smooth DEM transitions
        B. Clip low-resolution data sets pushed to 2-m resolution, such as Personal Watercraft data and regional DEMs, to minimal overlap
           with adjacent high-resolution data sets (usually multibeam and topographic lidar)
        C. Clip topographic lidar so that only a single dataset is used for the coastal zone.  Where it exists, the USGS lidar is given highest
           preference in the nearshore zone because it was collected in the summer and fall of 2010 when the beach morphology was less likely to
           influenced by winter storm events.  The Golden Gate Lidar Project data are used for all reaches landward of the USGS lidar coverage (roughly
           10-m elevation and higher) and along the coastline where USGS lidar was not collected.  The OPC lidar is present only in two small sections
           that are not covered by USGS or GGLP lidar (within DEM sections 1 and 14).
    7. Fill in data gaps between high-resolution datasets
        A. If no high-resolution data are available between the offshore multibeam bathymetry and coastal topographic lidar in protected
           harbors/embayments, or in other areas where interpolation from surrounding data sets will create a surface unlikely to reflect actual
           bathymetry/topography accurately, fill in gaps with regional DEMs or other low-resolution data sets. Otherwise, interpolate across gaps.
            I.   Filling in harbors or embayments using regional DEMs/other low-resolution data:
                 a) Clip best available regional DEM or bathymetry to gap area, allowing only minimal overlap (~20 m) with adjacent high-resolution
                    data sets
                 b) Export clipped grid as xyz, reimport as points, create TIN, create 2-m grid from TIN, clip to gap extent
            II.  Interpolation across nearshore gaps:
                 a) Create preliminary DEM using Mosaic tool with the following settings:
                    Coordinate System: UTM Zone 10 North
                    Pixel Type: 32 Bit Float
                    Cell Size:  2
                    Mosaic Method: Blend
                    Mosaic Color Map: Last
                 b) Create polygon of data gap(s) to fill within the preliminary DEM surface
                 c) Buffer the data gap polygon with a linear distance of 20 m using the Buffer tool in Arc Toolbox
                 d) Clip preliminary DEM using the buffered polygon, export clipped grid as xyz, reimport as points (fig. 3B), create TIN, create 2-m
                    grid from TIN, clip to buffered gap extent
            III. Interpolation around perimeter of Bolinas Lagoon and Drakes Estero:
                 a) Fill any narrow gaps between bathymetry grids of Bolinas Lagoon and Drakes Estero and the nearest high resolution topography
                    using the same procedure as used above for interpolating across nearshore gaps.
    8. Compile final DEMs
        A. Load all datasets for DEM
        B. Verify all significant data gaps filled (few missing cells OK) in DEM coverage area
        C. Build interim DEM using Mosaic to New Raster tool in ArcGIS with same setting as noted above in Step 7
        D. Build final DEM using Mosaic to New Raster tool in ArcGIS.  Input rasters are the above interim DEM and a grid of small islands or rocky
           outcrops obtained from lidar.  The islands are given top priority in the mosaicking algorithm so that island elevations from the lidar overwrite
           elevations from the nearshore interpolation.
        E. Clip output to DEM coverage area
        F. Create contours and plot cross-shore profiles to verify data quality and consistency
    
  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?
    Refer to the DEM Accuracy and Limitations section in this Data Series for an explanation of the accuracy of the identification of the entities and assignments of values in the dataset and a description of the tests used.
  2. How accurate are the geographic locations?
    Refer to the DEM Accuracy and Limitations section in this Data Series for an explanation of the accuracy of the horizontal coordinate measurements and a description of the tests used.
  3. How accurate are the heights or depths?
    Refer to the DEM Accuracy and Limitations section in this Data Series for an explanation of the accuracy of the vertical coordinate measurements and a description of the tests used.
  4. Where are the gaps in the data? What is missing?
    Refer to the DEM Construction Methods section in this Data Series for information about omissions, selection criteria, generalization, definitions used, and other rules used to derive the dataset.
  5. How consistent are the relationships among the observations, including topology?
    Refer to the DEM Construction Methods section in this Data Series for an explanation of the fidelity of relationships in the dataset and tests used.

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:
Not suitable for navigation. Read and fully comprehend the metadata prior to data use. Acknowledge the U.S. Geological Survey (USGS), the originator, when using the dataset as a source. Any use of trade, firm, or product names is for descriptive purposes only and does not imply endorsement by the U.S. Government. This information is provided with the understanding that it is not guaranteed to be correct or complete and conclusions drawn from such information are the responsibility of the user. Majority of data (that is, lidar, multibeam bathymetry) derived from topographic/bathymetry data collected at 1-2 m horizontal resolution,with vertical uncertainty at time of data collection ranging from 10 cm to 1 m. Use at greater scales not advised. See full Data Series report for more information: Foxgrover, A.C., and Barnard, P.L., 2012, A seamless, high-resolution digital elevation model (DEM) of the north-central California coast: U.S. Geological Survey Data Series 684, 11 p. and datasets, available at http://pubs.usgs.gov/ds/684
  1. Who distributes the data set? (Distributor 1 of 1)
    U.S. Geological Survey (USGS) Coastal and Marine Geology (CMG)
    Attn: Patrick L Barnard
    Research Geologist
    USGS, 400 Natural Bridges Drive
    Santa Cruz, CA
    USA

    (831) 460-7556 (voice)
    (831) 427-4748 (FAX)
    pbarnard@usgs.gov
  2. What's the catalog number I need to order this data set? U.S. Geological Survey Data Series 684
  3. What legal disclaimers am I supposed to read?
    Please recognize the U.S. Geological Survey (USGS) as the source of this information. Although these data have been used by the U.S. Geological Survey, U.S. Department of the Interior, no warranty expressed or implied is made by the U.S. Geological Survey as to the accuracy of the data. The act of distribution shall not constitute any such warranty, and no responsibility is assumed by the U.S. Geological Survey in the use of this data, software, or related materials.
  4. How can I download or order the data?
    • Availability in digital form:
      Data format: Compressed file including Arcinfo grid and metadata. (version 10.0) Arcinfo grid Size: 0.526
      Network links: http://pubs.usgs.gov/ds/684/
    • Cost to order the data: none


Who wrote the metadata?

Dates:
Last modified: 12-Jan-2012
Last Reviewed: 01-Feb-2012
Metadata author:
Amy Foxgrover
Geographer
400 Natural Bridges Drive
Santa Cruz, CA
USA

(831) 460-7561 (voice)
(831) 427-4748 (FAX)
afoxgrover@usgs.gov
Metadata standard:
FGDC Content Standards for Digital Geospatial Metadata (FGDC-STD-001-1998)

This page is <https://cmgds.marine.usgs.gov/catalog/pcmsc/westcoast/cencal/source_data_shp.faq.html>
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