San Francisco Bay and Sacramento-San Joaquin Delta DEM for Modeling, Version 4.1 (SUPERSEDED)

This product is superseded by version 4.2. See:
https://data.cnra.ca.gov/dataset/san-francisco-bay-and-sacramento-san-joaquin-delta-dem-for-modeling-version-4-2

## 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://water.ca.gov/-/media/DWR-Website/Web-Pages/Library/Modeling-And-Analysis/Files/Modeling-and-Analysis-PDFs/FINAL6BayDelta39thProgress-Report071918.pdf

##Domain and Product
Changes between 4.0 and 4.1 are documented in the change log below and are most pronounced in the Suisun Marsh region and in the incorporation of some improvements in the South Delta. 

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

New work reported here was done at 2m resolution, although the improvements have been incorporated into the 10m products as much as possible. Relative to the previous DWR release (https://data.cnra.ca.gov/dataset/san-francisco-bay-and-sacramento-san-joaquin-delta-dem-v3), the 2m DEM product reported here consolidates work at this resolution into a small number of larger surfaces representing approximately one-third of the Delta (link to the Coverage Areas page). Laterally, the 2m models now extend over the levee crest as needed to match well with Delta LiDAR (http://www.atlas.ca.gov/download.html#/casil/imageryBaseMapsLandCover/lidar2009 ), the main terrestrial source of data used in this work. The 10m product (link to the Coverage Areas page) is based on the updated USGS DEM (https://www.sciencebase.gov/catalog/item/58599681e4b01224f329b484 ). In places where updated 2m models overlap the 10 meters, the 10m base elevation model was updated by resampling the new 2m model and adding levee enforcement. At the border between the 2m and 10m models, the two resolutions were locally edge-matched over a small region to maintain smoothness. For more information, please refer to the report: A Revised Continuous Surface Elevation Model for Modeling (link to Chapter 5 in the 2018 Delta Modeling Section Annual Report (https://water.ca.gov/-/media/DWR-Website/Web-Pages/Library/Modeling-And-Analysis/Files/Modeling-and-Analysis-PDFs/FINAL6BayDelta39thProgress-Report071918.pdf).
Please note that by agreement with our data providers we distribute only our own integrated maps, not the original source point data.
(https://water.ca.gov/-/media/DWR-Website/Web-Pages/Library/Modeling-And-Analysis/Files/Modeling-and-Analysis-PDFs/FINAL6BayDelta39thProgress-Report071918.pdf 

###Version: 4.1
* Time Completed: December 2018
* Horizontal Datum: NAD83
* Spheroid:GRS1980
* Projection:UTM_Zone_10N (meters)
* Vertical Datum:NAVD88 (meters)

##Data Sources
https://data.cnra.ca.gov/dataset/san-francisco-bay-and-sacramento-san-joaquin-delta-dem-for-modeling-version-4/resource/981a57b5-e16f-4632-b7e0-4a533534a79c
##Coverage Areas
https://data.cnra.ca.gov/dataset/san-francisco-bay-and-sacramento-san-joaquin-delta-dem-for-modeling-version-4/resource/2e3f2b6e-9f0d-4719-b32a-dff449be18af

###Changes since 4.0
* correct the year of survey for COE single-beam (OBJECTID 25) from 1988 to 1988
* update 2m DEM for Montezuma Slough based on newly connected multibean data by NCRO (August 2018 for Montezuma Slough and Hunter Cut)
* cut the portion of DEM for Calaveras from v3 2m San Joaquin River (dem_calaveras_river_2m_20120902 
* Changes only occurs in part 1 of "dem_north_delta_2m_v4_20171220" (v4 final):
1.apply patch at the intersection of Sacramento River and Feather River;
2.add Fremont Weir from the 2m Yolo DEM
* The following modifications are applied to "dem_yolo_merge3_mod_20161202" (v4 final; D:\dem_list_review\yolo_bypass):
* Improved merge with Sacramento River on the north:
* Improved merge with 2m Shag/Stairstep dem (dem_shag_stairstep_toe_drain_2m_v4_beta_20150518.tif ) which goes beyond multibeam data, derived based on mixed single-beam datasets using GAM
* Improved patching and compatibility with USGS 10m release
* Create 2m DEM for the Old River between SWP/CVP to Five points based on new bathymetry data collected in June 2018
* Add the newly developed 2m Montazuma Slough DEM as part of v4 release. Update 10m Delta DEM to be consistent with this addition and update data source polygon accordingly.
*  Create 2m DEM for the Old River near Coney Island based on new bathymetry data collected in June 2018 
*  Incorporate modifications done for Yolo and North Delta into 10m DEM for Delta and Bay-Delta.
*  The 20181120 version of the 2m South Delta DEM missed a small region that is included in the old version
*  Add LiDAR to Shag Slough in 2m Yolo DEM (dem_yolo_2m_20181012), The existing DEM for Shag Slough did not extend sufficiently over banks.