Digital elevation model (DEM) of northern San Francisco Bay, California, created using bathymetry data collected between 1999 and 2016 (NAVD88)

Using ArcGIS, the source DEMs were displayed and areas that would need further interpolation were identified. The lineage, vertical datum, and resolution of each DEM surface were noted for order of precedence when constructing the combined DEM and need for resampling or datum conversions. Using the ArcGIS Mosaic to New Raster tool, the surveys that were from the same sources, and were not continuous surfaces, were assembled into two separate DEMs for areas both north and south of the channel in San Pablo Bay. Elevation contours were digitized across the two DEMs to constrain the interpolation across data gaps in intervals of 20 centimeters across broader shallower areas (generally in water depths less than 4 m), and in intervals of 1 meter in deeper areas. The two sections were converted from raster to points to use as inputs in the interpolation process. Using the ArcGIS Topo to Raster tool (ESRI 2015), the two sections of north and south point data were used, along with the newly drawn contours, to interpolate continuous DEMs at a resolution of 1 meter, using the contour as the primary interpolation constraint. The DEM for Carquinez Strait was one of three DEMs interpolated from single beam data. These DEMs were interpolated using the Topo to Raster method as described in Fregoso and others (2008). The Carquinez Strait section was the only section that was able to make use of topographic lidar for shallower sections adjacent to the shore. The channel data for San Pablo Bay and Suisun Bay are primarily multibeam data with varying resolutions, and in a different vertical datum from the rest of the data used in this project. The data were resampled to 1 meter using the resample tool in ArcGIS, and then converted to NAVD88 using NOAA’s VDATUM tool (https://vdatum.noaa.gov/). There were a few areas with data gaps that were filled using the Topo to Raster method from above. Once all data were in the same horizontal (UTM NAD83) and vertical (NAVD88) datums, the different DEMs were fitted together into a seamless DEM using the ArcGIS Mosaic to new Raster tool. In areas with obvious discrepancies between DEMs, edges were smoothed by clipping out a narrow gap between surveys then using contours and the Topo to Raster tool. The final pieces were all put together using the Mosaic to new Raster tool, and VDATUM was again used to create versions in both Mean Lower Low Water (MLLW) and NAVD88. The VDATUM tool did not have the full extents of the NAVD88 version available for conversion, so the outlines of the San Pablo Bay region do not match in both versions.

Edit was made to correct the Attribute Definition of the 'Value' attribute (from 'Elevation relative to MLLW' to 'Elevation relative to NAVD88'). No data were changed. Users are advised to compare the metadata date of this file to any similar file to ensure they are using the most recent version.

Edited metadata to add keywords section with USGS persistent identifier as theme keyword. No data were changed.