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post #11 of 16 Old 10-01-2016
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Re: Florida Navigation

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Originally Posted by UPHILL View Post
Are charts not in fathoms? -----
Or feet or meters.

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post #12 of 16 Old 10-01-2016
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Re: Florida Navigation

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Originally Posted by aeventyr60 View Post
How about the tidal range in that spot? Might just take a three foot tide to float your boat over that spot...
A big tidal change in that area is about a foot at best. That's why several Florida boat manufacturers came up with a flats boat, one that could skim over 6 inches of water and easily pushed along with a push pole while standing upon a platform over the outboard.



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Originally Posted by killarney_sailor View Post
In Indonesia we passed through an area that was shown as land when in fact the depth sounder could not even find bottom (generally this is >450' deep. Common sense and eyeball navigation works very well.
Dont need to go to Indo to see that! Theres a place on the Fla ICW that shows you clearly over land on the chartplotter while you are in the channel between the markers with 10' under you. With updated chart data.
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post #14 of 16 Old 10-01-2016
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Re: Florida Navigation

Here in the NE we wouldn't call five feet deep draft, we'd call it shoal.(G)

A peek at some online tidal sites says right now "sea level" is about two feet over mean low water in the Keys (with a tidal variation of less than a foot) so if the chart is drawn at mean low water, and right now (moon phase, winds, rain runoff) there's another two feet on top of that, the water depth could be four feet despite the chart.

Assuming the chart is recent, not 1840's. What's the date on it? (Yeah, electronics tend to omit that when they tile charts.) And accurate or certain was your position on the chart, and the position data used to mark that spot?

Charts at Jones Beach (LI, NY) twenty years ago were considered accurate and well accepted--but sometimes were off 1/3 mile compared to GPS.

And then there's the fact that the oceans are living systems, not static. Channels routinely scour out, I've been in a "forty foot" channel and measured over eighty feet to the bottom, courtesy of current scour. Of course if the coral was healthy, the bottom could go the other way as well.

Which is why I'm semi-serious when someone asks me about sufficient depth, and I say, if we don't have enough water to roll the boat without getting the mast stuck in the bottom, we don't have enough water.

If you've ever seen a shopping cart (?!), oil drum, or trashed 16' runabout sitting in ten feet of water and cutting it down to a six foot clearance...Yeah, the Keys and coral heads and all that fine stuff are very different from northern waters and rock ledges.(G)

BTW, NOAA still appreciates chart correction data and survey data being sent in from all vessels, so they can fix these things.
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post #15 of 16 Old 10-01-2016
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Re: Florida Navigation

No coral heads in that area - just turtle grass, sugar white sand, and some chunks of hard substrate in a bit deeper water, but overall, fairly soft bottom. Tarpon tend to forage at the particular location because of it's proximity to the cuts just above Stock Island, which during ebb tide wash out dollar crabs and a host of forage species. It's also a great place to hook up with grunt, which is among the best tasting fish in Florida. The grunt hold along the deeper edges of the cuts and feed on baby shrimp as the tide ebbs and carries them out of the turtle grass.

As for the GPS accuracy in that area, it's actually very, very good, though I'm sure the charts in the GPS are quite dated, probably back to the late 1940s or 50s. Many years ago, when Key West was still pumping out it's treated wastewater into the Ocean, there was an underwater discharge pipe about 1/4 mile from the beach that locals referred to as the Rose Bowel because of it's odoriferous waft when the wind was blowing from the south east. My GPS location of the Rose Bowel was within 20 feet of the actual pipe, which I consider pretty accurate. Also, the GPS found the day markers that marked the entrance to Mule Key Basin and the accuracy there was just a couple feet at most.

I'm fairly confident that the line drawn by the OP was on the money, and I'm also confident that recent storms could have easily washed that sand bar away, thus providing him with deep water to transit the area. The same thing happened at Boca Grande Key, where a popular sailboat anchorage can be found at the end of the Lakes Passage. At one time, back in the 1970s, it was very unusual to see a sailboat at that locations because the entrance had silted in to about 3 feet at high tide. Today, that same entrance is now about 8 feet deep and lots of sailboats utilize the anchorage area on a regular basis. That depth change was attributed to the passage of a powerful storm more than 2 decades ago. Unfortunately, I have not visited this location in more than a decade, and from the Google Earth photo it appears to have filled in once again, though because the water is gin clear in this location, it is difficult to tell.

If you happen to get to the Boca Grande Cut Anchorage, the tide screams through the cut during ebb tide but the bottom holding is pretty good because of the hard substrate. And, when the tide slacks, it's a fantastic location to catch lobster, huge grunts, mangrove snapper, small grouper, and cero mackerel. This location has provided me and others with lots of fantastic seafood dinners.



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Last edited by travlin-easy; 10-01-2016 at 05:12 PM.
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post #16 of 16 Old 10-01-2016
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Re: Florida Navigation

If you haven't noticed whether fathoms,feet or meters maybe the date,scale and compass rose/variation doesn't serve any purpose for you either.
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