Calibrating a map that is not 'True North' (PathAway 4.x)

Questions and problems regarding map calibration and conversion.

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msjfb
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Calibrating a map that is not 'True North' (PathAway 4.x)

Postby msjfb » Wed Mar 21, 2007 6:30 am

I have scanned maps I have for an upcoming boating trip. North is not 'up' on the maps.
Am I correct in understanding that I can use the scans 'as is' if I calibrate them in Map Manager using the 'known points' method and a minimum of 3 points ?

If not and I have to rotate the maps before calibrating, anyone have any suggestions as to how to do this ?

EDIT: When I say true north, I mean North is not straight up on the map.. Not a question about Magnetic North vs True North.

Thanks,

Frank

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Scott
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Postby Scott » Wed Mar 21, 2007 8:08 pm

When calibrating a map with "Known Points (skewed)", the map does not need to be perfectly "North Up". As long as the top of the map is within 45 degrees of north, then it can be calibrated correctly. If you need to rotate it, you can use any graphics imaging program, or even Windows Explorer to rotate the map in 90 degree increments until North is somewhat facing up.

msjfb
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Postby msjfb » Wed Mar 21, 2007 9:15 pm

That's great, thanks.
Is 3 points really enough : I was thinking of using 4 points (one near each corner) ^

Frank

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Postby Scott » Wed Mar 21, 2007 10:24 pm

The more points the better, as long as they are accurate. 3 will do if there is no curvature to the map.

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Postby Scott » Wed Mar 21, 2007 10:25 pm

Also, the further apart the points are, the more accurate the map calibration will be.

msjfb
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Postby msjfb » Wed Mar 21, 2007 10:35 pm

Your input is much appreciated. Thanks.


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