This is a MD iMAP hosted service layer. Find more information at http://imap.maryland.gov. Bathymetry for Chesapeake Bay and Coastal Bays was derived from two hundred ninety-seven surveys containing 3 - 178 - 509 soundings. Thirty-five older - less accurate - overlapping surveys were entirely omitted before tinning. Partial overlap from other older - less accurate surveys was also omitted prior to tinning. The surveys used dated from 1859 to 1993. Thirty-six surveys dated from 1859 to 1918 - thirty-seven from the 1930s - ninety-one from the 1940s - sixty- six from the 1950s - twenty-five from the 1960s - twenty-four from the 1970s - fourteen from the 1980s - and four from the 1990s. The total range of sounding data was 3.7 meters to -50.4 meters at mean low water. Mean high water values between 0.2 and 1.2 meters were assigned to the shoreline. Fifteen points were found that were not consistent with the surrounding data and were removed prior to tinning. DEM grid values outside the shoreline (on land) were assigned null values (-32676). Last Updated: Feature Service Layer Link: https://mdgeodata.md.gov/imap/rest/services/Elevation/MD_Bathymetry/MapServer ADDITIONAL LICENSE TERMS: The Spatial Data and the information therein (collectively "the Data") is provided "as is" without warranty of any kind either expressed implied or statutory. The user assumes the entire risk as to quality and performance of the Data. No guarantee of accuracy is granted nor is any responsibility for reliance thereon assumed. In no event shall the State of Maryland be liable for direct indirect incidental consequential or special damages of any kind. The State of Maryland does not accept liability for any damages or misrepresentation caused by inaccuracies in the Data or as a result to changes to the Data nor is there responsibility assumed to maintain the Data in any manner or form. The Data can be freely distributed as long as the metadata entry is not modified or deleted. Any data derived from the Data must acknowledge the State of Maryland in the metadata.