Re: [Paddlewise] GPS Errors

>From: "Dave Kruger" <kdruger_at_pacifier.com>
> Could be your GPS uses a different datum for its altitude determination than
> what is used for the tide book's "sea level."
>
> The tide book uses MLLW (= Mean Lower Low Water) as its zero point, while
> USGS topos use a National Geodetic Vertical Datum, usually the 1929 datum,
> which uses MHHW, I think, as "zero altitude."

Thanks, mystery solved.
Bob
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