San Francisco Bay and Sacramento-San Joaquin Delta DEM for Modeling, Version 4.2

# SUPERSEDED --> See version 4.3 
https://data.cnra.ca.gov/dataset/san-francisco-bay-and-sacramento-san-joaquin-delta-dem-for-modeling-version-4-3

## Citation and Main Description:
This product is described in Chapter 5 of the 2018 DWR Delta Modeling Section annual report, produced jointly with USGS.

 https://data.cnra.ca.gov/dataset/methodology-for-flow-and-salinity-estimates-in-the-sacramento-san-joaquin-delta-and-suisun-marsh/resource/84d4fd29-c839-4efa-82be-b58f7ed176db

##Domain and Product
This product is a mutually compatible suite of DEMs covering most of the aquatic and terrestrial areas of the Bay-Delta. The product was derived from original point data collections, lidar and other DEMs. Also included in the resources are images and shapefiles describing the source data. 

Changes between 4.1 and 4.2 are documented in the change log below. Changes prior to that are recorded in the 4.1 web page.

Changes in version 4 relative to prior products are limited to the region east of the Carquinez Strait (starting around Carquinez Bridge). To facilitate compatibility between products released by DWR and USGS/NOAA partners, DWR distributes the region west of the active work at 10m resolution but does not actively work in this region. The San Pablo Bay boundary of active revision in the present product in a place where its source data matches that of other Bay elevation models, e.g., the 2m seamless high-resolution bathymetric and topographic DEM of San Francisco Bay by USGS Earth Resources Observation and Science Center (EROS) (https://topotools.cr.usgs.gov/coned/sanfrancisco.php ), the 2010 San Francisco Bay DEM by National Oceanic and Atmospheric Administration (https://www.ngdc.noaa.gov/metaview/page?xml=NOAA/NESDIS/NGDC/MGG/DEM/iso/xml/741.xml&view=getDataView&header=none ) or the prior (version 3) 10m digital elevation model (https://data.cnra.ca.gov/dataset/san-francisco-bay-and-sacramento-san-joaquin-delta-dem-v3 ).The 10m DEM for the Bay-Delta is based on the first on the list, i.e. EROS’ 2m DEM for the Bay



###Version: 4.2
* Time Completed: December 2020
* Horizontal Datum: NAD83
* Spheroid:GRS1980
* Projection:UTM_Zone_10N (meters)
* Vertical Datum:NAVD88 (meters)

###Changes since 4.1
* Incorporate 1m DEMs from Cache Slough Complex (USGS, 2020) into 2m DEMs for Yolo and North Delta.
* Develop 1m DEM for Lindsey Slough Restoration area based on Handley DEM (UCD, 2015) and Lindsey Slough, Cache Sough, Liberty Island DEM (USGS, 2020) and and merge it into 2m Yolo DEM.
* Develop 2m DEM for Tom Paine Slough based on 2018 Bathymetry Survey (DWR, NCRO) and 2017 LiDAR (DWR) and merge it with 2m DEM for South Delta.
* Develop 2m DEM for Suisun Slough based on 2018 Bathymetry Survey (DWR, NCRO) and 2017 LiDAR (DWR) and merge it with 2m DEM for Montezuma Slough.
* Develop 2m DEM for Georgiana Slough based on 2019 Bathymetry Survey (DWR, NCRO) and 2017 LiDAR (DWR) and merge it with 2m DEM for North Delta.
* Develop 2m DEM for Sacramento River between its junctions with American River and Sutter Slough based on 2019 Bathymetry Survey (DWR, NCRO) and 2017 LiDAR (DWR) and merge it with 2m DEM for North Delta.
* Incorporate all the 2m additions and modifications done for Yolo, North Delta, Montezuma Slough and South Delta into the 10m DEM for Delta and Bay-Delta.