West of Golden Gate Currents

Our current programs are unique in that we compute current at EVERY point on the Bay. The display runs in real time, refreshed every 5 seconds. The example below shows the region outside the Golden Gate at max flood on the morning of September 18, 2005, at 11:20 a.m. PDT. This display option uses a streamer to show direction and gives the magnitude of the current in knots (in boxes). The blue boxes are default current locations, and the yellow boxes are additional displaypoints added by the user. You can concentrate points to show as much detail as you wish. Alternatively, you can choose the vector display, in which the length of current streamers are proportional to the magnitude of current. As this example shows, there are dramatic changes in current strength and direction in a westerly approach to the Golden Gate, both in a flood (below) and in an ebb.

These variations in current strength and direction have a significant effect on headings, course selection and laylines. In this example the boat is just outside the Gate and is heading upwind to a mark "35" just north of the ship channel. The colored lines joining boat and mark are the result of the routing solution produced by our tactical software. The fastest (optimum) route is shown in red, and comparison routes in other colors. The corresponding times are given in the "Best Course Comparisons" box, indicating that the red course takes a little over 86 minutes, more than 10 minutes faster than the black course, and almost 22 minutes faster than the blue course. Under these circumstances a course which plays the current differences along the north shore is most effective. Our tactical programs factor wind, current and boat polars to determine the optimum route.