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post #1 of 10 Old 08-09-2011 Thread Starter
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gps and lake contour maps

I sail on a lake in MN that has a wildly uneven bottom and some dangerously shallow spots. I have a fish finder that helps me stay out of trouble but I need additional gps help. I loaded Navionics on my Droid. Great detail of the lake bottom but I can't read the screen in sunlight and I don't think the GPS is accurate enough to keep me out of trouble. Handhelds are in my price range but the screen is so small I'd have to put my glasses on every time I wanted to read it. Bigger units are way too expensive. Can anyone recommend a system that has accurate gps (WAAS or DGPS) on top of good bottom detail and not a ton of money?
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post #2 of 10 Old 08-09-2011
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Unfortunately most of the electronic charts I tested are not detailed enough. It is best to use paper charts and be very careful when the chart indicates a shallow. It is much better to check the depths with echosounder when you arein a shallow area.
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post #3 of 10 Old 08-09-2011
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I lake sail as well in MN and find it difficult to find decent charts of the lakes. The DNR does have some but, you can't really navigate by them as the lat and long aren't there. Unfortunately I think you are stuck with getting to know your lake very well and using your depth sounder and GPS together. Making notes on landmarks and all that until you can get something with a larger screen. Utilizing something like SeaClear or Open CPN on a laptop won't work as I do not think you can get compatible charts for MN lakes. What lake are you on by the way? I am usually on Minnetonka. Depth not really an issue there, its the power-boaters...... If you find a resource for decent lake charts let me know.

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post #4 of 10 Old 08-09-2011 Thread Starter
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I got to sail MTKA a little this summer before moving to my buoy on Lake Buffalo. MTKA is marked well but Buff is not. I'd like to be able to just glance down and see my boat icon on top of a detailed Lakemaster or Navionics chart and know I was clear of the rocks. I'll let you know if I come up with something.
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post #5 of 10 Old 08-09-2011
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Lowrance has some of the better lake chips from what i have seen BUT of course they only work on Lowrance units

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post #6 of 10 Old 08-09-2011
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I don't know about your particular lake, but if you're happy with the detail level of the Navionics map and just want a better display and better GPS, I'd recommend an iPad for the display with an external bluetooth GPS puck. You can probably get a used 1st generation iPad relatively cheaply. You just need the cheaper WiFi model, not the 3G, since you'll be using an external GPS. And you don't need lots of memory, the 16GB model will do fine. I'm not sure what the external GPS pucks cost, but I don't think they are too expensive.

Overall I think this system will be cheaper than a dedicated large screen GPS unit, and more flexible. Drawbacks will be you might have some difficulty in direct sunlight (although I've used my iPad outside without any trouble), and of course the iPad is not 'marine grade', so if it gets wet, you're in trouble.

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post #7 of 10 Old 08-09-2011
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I use a netbook, downloaded PolarNavy, installed charts, and bought a puck for $39 and a water-resistant cover for $19 or so. Still hard to read in direct sun, but it's well protected and I have a 7-in navigation screen just inside the companionway door, out of the direct glare. Pretty cheap solution. I'm on inland waters. Using the same netbook for internet, watching movies, office applications, etc.

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post #8 of 10 Old 08-10-2011
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Heybuddy,

I think the size of the display you need depends on where you plan to use or install it. If you have wheel steering with a pedestal you can get by with a smaller unit. If you are going to mount it on the cabin bulkhead and you steer with a tiller six feet away, and your eyes are not as good as they used to be, a larger display is called for.

I sail Minnetonka in a 23' boat with tiller steering. I have a RAM mount for my Lowrance Ifinder at the back of the boat on the lazarette. I can turn it to face me no matter what tack I am on. The Lakemaster charts with detailed depth contours are excellent. I don't really need them since I've been sailing this lake for 35 years. But they are cool! I'll have to check if Buffalo Lake is included on my chip the next time I go out.

The Lakemaster SD card I have for my Ifinder is encrypted, copy protected, and cannot be read on a computer or Ipad, at least not legally. For those of you sailing the coasts or the Great Lakes, free NOAA electronic charts are not available for inland lakes. A small number of lakes have electronic charts available for free that have been created by individuals or groups. But for the most part we are stuck with using proprietary charts or chips that are designed for their own specific hardware.

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post #9 of 10 Old 08-10-2011
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heybuddy-
Sunlight readable screens come in two flavors: Small, or damned expensive. Tablets won't be easily readable, neither will cell phones, so you're left with purpose-built GPSes and chartplotters which are going to be expensive.
The alternative is to sail at night. Or wait five years for new screens to come out.

Pretty much all the GPSes today will have WAAS, but DGPS is uncommon in the civilian market. WAAS accuracy is best on the east and west coast, where the corrections are based. In the heartland...I think you'd find the stated 3-meter (+- ten feet, for a 20 foot potential error) accuracy might be stretched simply because you are at the extreme edge of the correction area.

So you're left with buying a marine GPS that suits your prices and has charts for your lake, and you'd probably better put avoidance zones a good 20' outside the spots you want to avoid. Assuming you respond to those alerts instantly.

That's just where it is.

One thing you may want to look at, if you don't wear precription sunglasses, they now sell sunglasses with bifocal reader lenses in them. Small ones in standard diopters, $10-15 in the flea markets and discount stores, just for purposes like this.

If you have rx or favorite sunglasses without a bifocal, look for the "stick on" vinyl bifocal lenses, about $25-35 online and hard to find in stores. They stick on to your glasses and they're incredibly effective for driving or boating, where you need occassional reading vision at arm's length. People think they have to be crap. Nope, they're actually incredibly good. And best of all, you get to position them exactly as high as you want them, or as small and low as you want them.
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post #10 of 10 Old 08-10-2011
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I'm a fellow MN lake sailor and use a Lowrance iFINDER H2Oc handheld GPS with a lake chip that covers MN. You can scroll in very close, or pan out and see the entire lake. I usually take a look at it before entering a new area and mentally note the shallow spots. I don't really use it for depth while sailing, but it would be possible.
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