In article tZRfd.10435$df2.5362@edtnps89,
"Gordon Wedman" wrote:

In " The Radar Book - Effective Navigation and Collision Avoidance " by
Kevin Monahan, he points out that the compass bearing given by a GPS will be
unstable at low speeds. If you want your radar to show proper compass
bearings and work in the North-up/Course-up modes he says you must connect
to some type of fluxgate or gyro compass. So if you just connect your GPS
NMEA output to your radar it seems you may not get correct heading
information while creeping along at low speed, for example, in fog.

That would very much depend on the GPS, its Position Update Rate, and
internal Math Capabilities. I would suspect that any GPS that updates
faster than every .5 Sec, and has a good floating point processor, would
give good resolution down to at least 2 to 3 knots.

Bruce in alaska
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