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Old 14-08-2013, 13:17   #1
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Chart Datum Question

I notice my chart datum is off. Is there a way to adjust it correctly? I am using cm93 charts and I honestly didn't sail across the land , I went through the passage...
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Old 14-08-2013, 13:35   #2
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It's just the survey the charts are drawn from being inaccurate in spots.
This is why you shouldn't believe chartplotters as gospel.
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Old 14-08-2013, 14:34   #3
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Re: chart datum question

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Originally Posted by monte View Post
I notice my chart datum is off. Is there a way to adjust it correctly? I am using cm93 charts and I honestly didn't sail across the land , I went through the passage...
Yes there is. it's all explained here -> CM93 Offsets | Official OpenCPN Homepage

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Old 17-08-2013, 18:46   #4
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Re: Chart Datum Question

The cm93 offsets can be easily determined using the GE2KAP program.


The latest GE2KAP is at Download*
A detailed explanation is in the Help section of the GE2KAP program.

Paul Higgins has made this an easy thing to do

Terry
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Old 17-08-2013, 20:38   #5
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Re: Chart Datum Question

Thats just bloody Scary!!
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Old 17-08-2013, 21:07   #6
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That explains the bottom paint on my rose bushes.
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Old 18-08-2013, 00:43   #7
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Re: Chart Datum Question

thanks guys, I see it ust offsets for the current chart in use. I guess you need to adjust them all individually. (after you figure out the correct offset)
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Old 18-08-2013, 00:48   #8
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Re: Chart Datum Question

A little care needs to be used when attempting to use Google Earth to correct CM93 charts as it can have its own errors. See "Imagery resolution and accuracy" at:

Google Earth - Wikipedia, the free encyclopedia

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