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Discussion Starter · #1 ·
I was looking at the bluechart today on my new gps and noticed that the water at the entrance to the del bay from bayway is 3ft at low tide but when i checked the tide chart page on the gps it stated at low tide there is less than 1 foot of water in the entrance-can someone help me out here and also on the bluechart for gps are the depths shown in ft or something else and it is always shown as the lowest water for that area?

[ 11-27-2005, 10:07 PM: Message edited by: REELKNOT ]
 

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I've never run aground there. I know it's shallow but quite a few inboard boats use it. On the other hand I heard it's being dredged this winter. :D
 

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Discussion Starter · #3 ·
just wondering-i have an outboard and was just trying to get a feel for the area-only so much you can learn from a gps while sitting at home.
 

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Believe it when it says there's 2 feet of water there. You know when you hear a boat rolled over in the rips? That's the spot! I know. I took one right over the stern some years ago.
 

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Discussion Starter · #5 ·
YEAH BUT WHICH IS MORE ACCURATE THE TIDE CHART ON THE GPS STATING LESS THAN 1 FOOT OF WATER OR THE BLUECHART STATING 3 FEET OF WATER?
 

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What is the low water mark?

Mean Low Water
Lower low water
Lower low water datum
Mean Lower low water?

My guess is either the age of the charts or the actual low water readings are not identical
 

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Originally posted by REELKNOT:
YEAH BUT WHICH IS MORE ACCURATE THE TIDE CHART ON THE GPS STATING LESS THAN 1 FOOT OF WATER OR THE BLUECHART STATING 3 FEET OF WATER?
The "bluechart" gives you mean lower low water as indicated, in feet. The "tide chart on your GPS" as you're referring to it, gives tidal departures from mean lower low water. I think that's where you're getting confused. Recently, I believe the low tide has been above, or deeper, than mean lower low water. I just tried to check on Boatersbox and the graph wouldn't come up.

For example, your SPOT you want to fish says it is 3 feet deep on your chartplotter. You then hit "tides" on your chartplotter menu. It indicates high tide of 4.5 feet for your SPOT for that day. You can expect to find water 7.5 deep at high tide at your SPOT.

[ 11-28-2005, 08:58 PM: Message edited by: TWIN D'S ]
 

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Phil,
Now reading what you said, makes more sense.

I misunderstood what reelknot was saying. I thought he meant that a paper map showed one foot of water.

According to my tide charts, The least change in the tides is during the first quarter and last quarter moon phases.

right now at the last quarter, the low tide is about 1 foot above normal. At full or new moon, the tides are slightly lower than normal for the ebb and slightly higher for the flood tides.
 

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Exactly Jason. I misunderstood what he was saying the first time too.
 

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Discussion Starter · #10 ·
i am confused-are you saying that the graph on my chartplotter(which is a copy of a paper chart put on a bluecard chip)reads 3 foot at the entrance of bidwell creek which is the low mean tide but when i look at the tidal chart on the gps(which is actual time)it shows 1 foot of water.so my question is-which is more accurate-i would think the actual tide perdiction chart.
 

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Discussion Starter · #11 ·
i think i am getting it-too many long hours at work-thanks
 

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Discussion Starter · #12 ·
I AM LOOKING AT MY GPS NOW ON THW CELESTIAL PAGE.IT SHOWS BIDWELL CREEK ENTRANCE AND SHOWS THE TIDES AS FOLLOWED- AT 1:22 AM 0.0FT 7:28 AM HIGH 6.9FT NOW DOES THE 0.0 FT MEAN THAT THERE WILL BE NO CHANGE IN THE WATER DEPTH?
 

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Originally posted by REELKNOT:
I AM LOOKING AT MY GPS NOW ON THW CELESTIAL PAGE.IT SHOWS BIDWELL CREEK ENTRANCE AND SHOWS THE TIDES AS FOLLOWED- AT 1:22 AM 0.0FT 7:28 AM HIGH 6.9FT NOW DOES THE 0.0 FT MEAN THAT THERE WILL BE NO CHANGE IN THE WATER DEPTH?
Yes, it means that the depth indicated on the chart for low tide will be just that. The high tide will be 6.9 feet higher than the depth on the chart. In coming days, you will see low tide look something like -.4 feet etc. This means the water will be .4 feet lower that what's on your chart. Of course, this assumes that both the GPS and chart are using the same reference, MLLW etc.
 

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Discussion Starter · #15 ·
GOT IT-SORRY FOR THE CONFUSION.THANKS GUYS
 

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It is important to know when the survey was done and when the chart was printed. The highs spots and lower holes in the bottom of the water, especially near inlets change every year. Winter does a lot of moving and shaking to the waters and it's bottom. As far as Bidwell creeks entrance, yes there is a shallow spot right at the end of the rocks. Probably less than 2' on an extremely low tide. I personally didn't think it was as shallow this year as it was last year.
Charts are only approximate and not to bet your life on. Always stay on the side of caution.
 

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Discussion Starter · #17 ·
I HEAR YA-I HEARD THEY MIGHT BE DREDGING BIDWELL ENTRANCE.THANKS CAPT
 

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Just remember...weather conditions can cause the astronomical predictions to be off quite a bit...like much higher or lower than expected or the range may be next to nothing in some areas....
 
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