GPS Velocity Measurement
Bill Combs (ttursine@gnt.net)
Sun, 22 Nov 98 14:46:48 -0600
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West Wight Potter Website at URL
http://www.lesbois.com/wwpotter/
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>We launched and headed up Redwood Creek, running mainly at 50% power while
>trying to monitor speed with our Garmin GPS II Plus. But the speed varied
>too much, from around 1.5 to 3.4 kn, to get a definitive speed to be
>expected at that setting, probably due to varying currents.
Reiterating a caution: the variance is probably due to Selective
Availability. Commercial GPS cannot be expected to give accurate
speed readings at small sailboat speeds due to this DOD-inspired
farce. I won't burden you with the math, but be aware that slow
updating (if your unit offers a choice) and a *lot* of mental
integration is required to get realistic readings.
Regards,
Bill Combs
WWP 19 #439 (1987), "Ursa Minor"
Fort Walton Beach FL
ttursine@gnt.net