Bathymetry and Acoustic Backscatter—Estero Bay, California

Survey Results

Estero Bay

The Estero Bay survey (Field Activity ID: S-05-12-SC) consisted of 117 survey lines totaling more than 580 linear kilometers of data. Depths ranged from 45 to 250 m relative to NAVD88. The multibeam bathymetry and coregistered acoustic backscatter cover the outer portion of Estero Bay, where the Hosgri and Los Osos faults merge (figs. 5 and 6).

After filtering the data to remove obvious outliers, the standard deviation of the remaining sounding elevations was calculated for each 2 by 2 m and 4 by 4 m cell (containing an average of 5 soundings for each 2 m cell and 12 soundings for each 4 m cell) in CARIS (fig. 7). The mean standard deviation for all cells in the Estero Bay survey is 0.12 m, and 95 percent of the cells in the data set have a standard deviation of less than 0.30 m (fig. 8). There are a few outlier cells with standard deviations as high as 1.09 m that are used in the final product. Most of the outlier cells occur in areas of high relief where high values are common.

Vertical uncertainty increases with depth, and IHO standards account for this in their specifications of survey quality. A comparison of the estimated bathymetric uncertainty (TVU) in this survey against IHO standards can be seen in fig. 9. Most of the elevation uncertainty in the dataset satisfies the IHO standard for special-order surveys (assuming the special-order standards were extrapolated to deep water); however, there are outlier cells that exceed the special-order threshold, but are within the first-order threshold. The TVU map can be used to generate a map of the IHO survey order satisfied by each cell in the DEM, as shown in fig. 10.

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