Consumer GPS is accurate to 8-10ft 95% of the time ...
When the boat speed is less than 0.6mph - the boat is not actually moving far enough on the water (greater than 8-10ft) for the GPS to effectively define that the "boat actually moved" - so the boat icon changes to a circle to indicate that the GPS is "waiting" for more defined information that the boat "actually moved past that 8-10ft barrier" ...
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Now, given the fact above about the inherent accuracy/inaccuracy of GPS systems -- And the fact that the HB Chart Defaults to "North Up" any time that the GPS cannot determine Course (example below 0.6mph as defined above)...:
Thus :: if the Chart Orientation is set to "Course Up" or "Head Up" - and the boat speed decreases below 0.6mph (GPS inherent inaccuracy) = the Chart Defaults (spins) to the "North Up" orientation ...
And once the boat speeds up to 0.6mph (GPS accuracy again) the Chart orients back to the user defined setting of "Course Up" or "Head Up"...
This can be confusing when the boat is travelling right at that 0.5-0.6mph variation in speed because the Chart is spinning from its user selected setting (Course Up or Head Up) to Default North Up ...
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To "fix" the spinning Chart (if the boat is going to be traveling at that 0-5-0.6mph barrier) is set the Chart Orientation to North Up (the same as the default Chart setting when GPS cannot determine course) ...
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The AS GPS HS antenna also "fixes" the spinning Chart issue buts it's not a "plug and play" option for HELIX 7 ... It requires some wire spicing ...
http://www.humminbird.com/Category/S...HELIX_EXT_GPS/
Rickie


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