How Does The S10 Calculate VMG?
The S10 calculates the heading from the downwind reference point to the upwind reference
point. This heading is assumed to be the wind direction. Since the only information
derived from the reference points is this heading, the position of the reference points in
absolute terms does not matter. The only thing that matters is the position of the upwind
point relative to the position of the downwind point.
The S10 takes GPS readings every second to get your actual speed as well as the heading
of your course. The device then multiplies your speed with the cosine of the angle between
your heading and the wind direction to extract the component of your speed that is aligned
with the wind direction. This process is repeated every second. Some averaging is then
performed to make the output smoother and easier to interpret. The results are displayed
on the LCD screen.
How accurate is the S10?
In speedometer mode the accuracy of the S10 is better than +/- 0.2 knots (0.36 km/h). In
VMG mode accuracy of the S10 depends on what angle to the wind you are sailing but is
generally better than +/- 1 knot (normally closer to +/- .3 knots).
FCC Compliance Statement
This equipment has been tested and found to comply with the limits of Part 15 of the FCC
Rules. These limits are designed to provide reasonable protection against harmful
interference in a residential installation. This equipment generates, uses and can radiate
radio frequency energy and, if not installed and used in accordance with the instructions,
may cause harmful interference to radio communications. However, there is no guarantee
that interference will not occur in a particular installation. If this equipment does cause
harmful interference to radio or television reception, which can be determined by turning
the equipment off and on, the user is encouraged to try to correct the interference by one
or more of the following measures:
- Reorient or relocate the receiving antenna.
- Increase the separation between the equipment and receiver.
- Connect the equipment into an outlet on a circuit different from that to which the receiver
is connected.
- Consult the dealer or an experienced radio/TV technician for help.
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