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post #36 of Old 02-25-2014
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Re: How much do you use your Chartplotter?

Originally Posted by shananchie View Post
...Many years ago, my daughter did a school science project on GPS and nautical charts. We picked a bunch of spots in Biscayne Bay and the Upper Keys. A significant number of locations and channel markers were off, some by many hundreds of feet...
What was the source of the error? Were the NOAA charts incorrect? Or was it just Garmin's (Raymarine's, etc.) translation of the NOAA chart? Or was the GPS fix off by many hundreds of feet (which I've never seen before)?

I ask this because I've always been suspicious of the embedded proprietary charts in electronic devices. Garmin's embedded charts for USVI and BVI can be off by hundreds of feet. Even NOAA's are off in that area, especially #25641 which is off by 1000 feet at Jost, Tortola, and eastern St. John.

But in the coastal US, IMO a chartplotter that uses NOAA's actual charts is more reliable than a proprietary chartplotter that attempts to replicate NOAA's data. The latter can always be susceptible to translation errors. That's one of the reasons I use a computer-based chartplotter that allows me to download NOAA's most up-to-date charts directly from their website.

Here's what I'll have mounted at my helm this year in dry weather. When it's raining, I'll move it down below or put it in my Travelon waterproof pouch:

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1998 Catalina 250WK Take Five (at Anchorage Marina, Essington, on the Delaware River)
1994 Mason 44 Firefly on loan from my BFF (West River, Galesville, MD)
1991 15' Trophy (Lake Wallenpaupack)
1985 14' Phantom (Lake Wallenpaupack)

Last edited by TakeFive; 02-25-2014 at 08:03 PM.
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