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The intertidal zone depicted in this feature class (FC) begins at the upper extreme at the shoreline derived from Washington Department of Natural Resources (and accepted into the federal standard USGS National Hydrologic Database). This shoreline is significantly off in places, relative to the accuracy needed to show shellfish beaches. The result is that this FC also contains polygons that fill the gap between the standard and actual shorelines (per more modern aerial imagery), but nowhere do polygons exist to correct for marine waters over depicted land.The low extreme extends as far as could be discovered in the best available photography, meaning comparing and choosing imagery from each of several years and selecting the set that showed the lowest water (most land) for swaths of shoreline. This was also compared to the imagery available from the Washington Department of Ecology’s oblique shoreline imagery web site, where there are also a few years’ of imagery available. Mostly though, the 2002 imagery was found to show the lowest water. It is unknown what classification of tide level (mean low, extreme low, etc.) ends up being shown, but it is the lowest justifiable from imagery. |