Imperial Beach Mapped Sand Elevations

Mapped sand elevations at Imperial Beach. Elevation maps are created on the same grid as the binned observations, but are smoothed and fill in small data gaps. For each survey, bins containing less than 3 data points are considered unsampled and are discarded. Map boundaries are defined as grid points that are regularly sampled during unnourished quarterly full surveys (must be populated at least 25\% of the time as the most frequently full surveyed grid point, during times without nourishment). Grid points with an unnourished average depth greater than 8m are not mapped because speed of sound errors due to stratification may contaminate jet ski sonar measurements. When the estimated interpolation (or extrapolation) error is large (NMSE>0.2), the map bin elevation is considered missing and filled with the value -99999.