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New Toy - Velocitek SC-1

Well, I couldn’t resist any more… I finally succumbed to the temptation and bought a Velocitek SC-1 GPS-based Speedometer/Compass/VMG/Timer.   Made by a little outfit in Hawaii, the SC-1 can display real-time speed, heading, or VMG, all based on a GPS signal.  It also includes a start timer, and can even display proximity to the start line when you’re in the pre-start for a race. The VMG function, which displays your VMG relative to a wind direction that you enter into the unit, will be very useful in figuring out the best angles to sail downwind on the Viper 640.  Being fairly new to the viper, this is an area I really need to work on.  I’ve been playing with GPS on my sailboat for quite a while, and even created a little utility to help set up a “regular” GPS to display VMG relative to a heading, to mimic the functionality of a Velocitek SC-1 (see download page).  However, there’s no substitute for the real thing… The SC-1 has HUGE, easy to read numbers on the display, a much faster display update rate than a “regular” GPS like the old Garmin handheld unit I was using before, and a much simpler user interface.Perhaps most important, it calculates and saves your speed data using the most accurate method: doppler shift measurements off the GPS sattelite signals.  All other “regular” GPS units, like my old Garmin, don’t store doppler information in their track data, so when you analize your speed on your PC, the speed has to be calculated via “time/speed/distance” calculations between individual GPS “breadcrumbs” in your track file.  Given the positional error possible for each track point, this calculated speed can obviously fluctuate quite a bit. I’m working out the best mounting solution for the SC-1 on the Viper 640.  More photos and GPS replays to come once I have the unit in the boat and have had a chance to play with it some more.