charts vs plotters

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PGFISHER

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We boat on lake mead; and I've been thinking of getting a chart plotter. I know the lake very well and use charts too. I go on line or call to find the water level. as the lake changes daily, and mentally correct the chart to find the new shorelines and shallows. Can I program a chart plotter with the water level to get true readings? If not ; there seems to be no sense in spending that kind of money, as I would have to correct anyway.
 
dingbat

dingbat

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Re: charts vs plotters

PGFISHER said:
We boat on lake mead; and I've been thinking of getting a chart plotter. I know the lake very well and use charts too. I go on line or call to find the water level. as the lake changes daily, and mentally correct the chart to find the new shorelines and shallows. Can I program a chart plotter with the water level to get true readings? If not ; there seems to be no sense in spending that kind of money, as I would have to correct anyway.
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No. A chart plotter only displays what data is embeded in the maps. If you want to know how deep it is, you'll need a depth finder.
 
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PGFISHER

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Re: charts vs plotters

I have a depth finder, but the transducer is on the stern. To be of any real use, I'd have to hang it from a 2000 foot boom on the bow. There needs to be a program that draws a dark or colored line on the map at the chosen depth to find the shore and shallows, or a chart plotter is useless. I don't need to know how deep it is where I've been; but how deep it is where I'm going.
 
dingbat

dingbat

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Re: charts vs plotters

Interphase makes a real nice unit that does exactly what you want to do. At $2,400 its a bargin.
 
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Pez Vela

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Re: charts vs plotters

PGFISHER said:
There needs to be a program that draws a dark or colored line on the map at the chosen depth to find the shore and shallows, or a chart plotter is useless.
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Many charts display a shallow water contour line which delineates the shallows along the shoreline. This shallow area is shaded in a different (usually darker) color so that it is readily apparent when you are entering "short" water. On Raymarine chartplotters, you may adjust the depth setting at which the shallow water contour line is drawn. If the Lake Mead chart you choose incorporates the shallow water contour feature, you would be able to adjust it to allow for water level fluctuations. The chart's "spot" depth readings would not change, but the shallow water contour would be extended further offshore (by your setting) as the water level drops, thus providing the safety margin you seek.
 
bruceb58

bruceb58

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Re: charts vs plotters

Pretty much worthless at Lake Mead. The only time I have messed up a prop there is going into a cove and hitting a rock sticking up right in the center of it. No way that would have been on a chart and it was only an issue because the lake was down a bit.
 
dingbat

dingbat

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Re: charts vs plotters

bruceb58 said:
Pretty much worthless at Lake Mead. The only time I have messed up a prop there is going into a cove and hitting a rock sticking up right in the center of it. No way that would have been on a chart and it was only an issue because the lake was down a bit.
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And that is exactly why using a chart to "confirm" the depth isn't practicable or advisable. Not to mention the chart of Lake Mead (NOAA 18687) was last updated 10 years ago.
 
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themaniam1

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Re: charts vs plotters

I love having my charplotter and it shows me where I am and how to get to places even in the dark. I boat in Powell with is very similar to Mead and I do agree that depth in usually not a concern because it is a deep canyon (500'+) with very few shallows. Lake Powell will drop 35' this winter to help Mead gain some volume with is supposed to raise Mead 20'+ and then Powell will net +10' over all which is a 45' swing. The charts show all the major mounds rocks that could become a hazard but like the chartplotters everything is at max water level so you have to do mental math to figure out how much to subtract of of the charts. If you in put the current water level on the chartplotter that is what would be sweet. I mine does not do this.
 
dingbat

dingbat

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Re: charts vs plotters

like the chartplotters everything is at max water level
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Depths shown on charts are the least depths to be expected under average conditions, not the maximun water level.

The soundings in tidal water are typically MLLW or MLW. The soundings on lakes are usually based off the mean elevation of the lake. The soundings on the Lake Mead chart are based of an elevation of 1160' above mean sea level.
 
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PGFISHER

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Re: charts vs plotters

$2400.00 is a bit expensive; but knowing that the charts ar at 1160' helps as a starting point. I thank everyone for their input, and agree that every rock and shallow isn't shown. I can point out a few hundred that would get you in trouble. I just wanted a good idea as to how deep they are.
 
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