GSL Bathymetry
David Tarboton 11/6/15

Files
gsldembiowest. Bathymetry grid obtained from Biowest.  This is with respect to NGVD29 vertical datum.
GSLDEM.tif  Elevation DEM Extended from the biowest DEM to include areas in the west desert that the lake may extend into at high elevation. This is also with respect to the NGVD29 vertical datum.
GB_Bathy.zip.  Zip file with contour source data from Glen Busch used by biowest in developing bathymetry.

Details
The Biowest bathymetry DEM was created by mosaicing these multiple elevation datasets into one contiguous elevation dataset for the entire Great Salt Lake Area. In general, elevations above 4200 are derived from the 10-meter NED DEM downloaded from the AGRC in the summer of 2010. NED Heights were converted from their native NAVD 1988 elevations to NGVD prior to merging with the bathymetric DEM. Elevations at and below 4200' are derived from various bathymetric data. Both the North and South arm are from USGS (Baskin, 2005 & 2006). Farmington Bay is from Baskin (unpublished, 2009) and modified by BIO-WEST in 2010. Modifications include minor contour manipulation and the introduction of a 4200 contour at the south end of the bay. Bear River Bay was surveyed by Hansen & Associates in 2009 under a contract with BIO-WEST, Inc. Trapezoid area is from BIO-WEST survey in May 2011. DEMs were created from bathymetric contours by first creating TIN from the contours utilizing vertices as mass points. Mosaic to New Raster was used to merge bathymetric DEMs with the upland DEM. It was done such that bathymetric values would replace the upland values at and below 4200. Finally, another mosaic was performed to fill minor imperfections at the edges of adjoining DEM's to fill in the no data values of GSL DEM.  

Baskin, R. L., (2005), "Calculation of Area and Volume for the South Part of Great Salt Lake, Utah," Open-File Report 20051327, USGS, Salt Lake City, http://pubs.water.usgs.gov/ofr20051327

Baskin, R. L., (2006), "Calculation of Area and Volume for the North Part of Great Salt Lake, Utah," Open-File Report 20061359, USGS, Salt Lake City, http://pubs.water.usgs.gov/ofr20061359.

The GSLDEM.tif file was created by 
(1) Obtaining a 10 m national elevation dataset (NED) DEM for this area.
(2)  Subtracting 0.97 m from this DEM to convert to NGVD29 vertical datum, for consistency with gsldembiowest.
(3) Mosaicing the two DEM's together giving priority to gsldembiowest.  This means that the NED DEM was only used to extend beyond the area covered by gsldembiowest.
(4) Clipping the resulting DEM to approximately 5 km beyond the 4225 ft contour.