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Guest taybri

2D - 3D question

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Guest taybri

What does the 2d-3d modes do on my Magellan 315? I notice that the lat/lon readings change when I toggle between modes? Is on more accurate, preferred? Any help appreciated.

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Guest Mike_Teague

2d is only giving lat/lon (horizontal), 3d is lat/lon/altitude (horizontal + vertical)

 

Since you need more satellites in view (4 instead of 3) for a 3d fix, 3d would be more accurate..

 

Usually in 2d mode, the unit will allow you to enter an altitude.. It uses that figure to solve for a more accurate horizontal position... If you ever are flying in an aircraft up 5+ thousand feet, turn off the gps, turn it on back on the ground in sub-optimal conditions, you might see a mile-plus horizontal error until it can get a new 3d fix with 4 sats... The gps uses it's "last known" position in figuring out where it is initially.. if you only have a 3 sat position, the altitude it thinks you are at will become part of the error..

 

So, always leave it in "3d mode" unless you're getting REALLY bad reception, and KNOW your altitude...

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