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tav
Joined: 05 May 2010
Posts: 49
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 Posted: Fri Oct 11, 2013 11:31 am Post subject: natical charts |
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been looking at some free charts online and just wondering are those
depths on the chart....are they at your typical low tide? trying to understand the map system and identify structures. |
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SeaDog1
Joined: 21 Dec 2009
Posts: 2629
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| Posted: Fri Oct 11, 2013 7:44 pm Post subject: Re: natical charts |
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| tav wrote: | been looking at some free charts online and just wondering are those
depths on the chart....are they at your typical low tide? trying to understand the map system and identify structures. |
Nautical charts are produced by the US NOAA Hydrographic Survey Service in feet and fathoms of depth.
The datum used to list depth is (LAT) "Lowest Astronomical Tide"
In some areas due to tidal flow the datum used to list depth is (MSL) "Mean Sea Level"
Datum used for vertical height is (HAT) "Highest Astronomical Tide" or highest spring tide to top of say a lighthouse or cable strung across a waterway.
Hope this answers your question.
SeaDog1 .... USCG Unlimited Licensed Master Mariner |
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