San Francisco Bay bathymetry methods

San Francisco Bay bathymetry methods

1. Obtain the most recent published depth soundings and shoreline data
2. Plot soundings and contour soundings. The South Bay figure here contains over 100,000 points and depth-colored contours.
3. On closer examination we can see the individual points and identify inconsistencies. This figure shows depth contours with colored, labeled soundings.
4. Check for errors. Here is an example where incorrect depth codes were assigned to shallow water soundings. A depth code for meters was assigned, the soundings were actually decimeters.
5. Final grid produced using the ArcInfo command Topogrid.
6. Datum adjustments for MSL, MHHW, NGVD. Since the adjustment for various tidal and non-tidal datums is not constant or is a simple function of distance, we use cotidal contours developed by the TRIM model. In this figure the cotidal contours are shown.
7. Based on the tide records at stations around the perimeter of the Bay we can assign adjustment values to these cotidal contours and produce an adjustment grid. The example given here is the adjustment grid for MLLW to MHHW.