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  #21  
Old 03-05-2014
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Re: GPS Accuracy - how much is actually needed

No matter how accurate your GPS lon/lat fix, it will never improve the accuracy of the underlying chart that you use. In some areas (like my home port) that charts seem to be highly accurate. In other areas (BVI) the charts can be off by as much as 0.5 nm, depending on which "chip" you purchase or charts you select (NOAA inaccurate, NGA accurate). I've posted many demonstrations of this before, but don't have time to hunt them down right now.

Quote:
Originally Posted by Alex W View Post
...For about the same price as the external NMEA 2000 GPS sensor you could buy a tablet that would give you a remote display from the A67 that is usable below decks. Any Android or iOS tablet will do it.
...or smartphone or Win8 tablet.

FYI, the Lenovo Miix 8" tablet that I have purchased (with internal GPS chip) has been seeing periodic price drops to $200 on Amazon. Just install OpenCPN, download NOAA's charts (preferably onto a 32GB microSD card), and install/configure GeolocationTCP, and you've got a really nice portable chartplotter for US use:

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  #22  
Old 03-05-2014
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Re: GPS Accuracy - how much is actually needed

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Originally Posted by TakeFive View Post
...or smartphone or Win8 tablet.
Since the OP has a Raymarine A67 I said iOS or Android because the Raymarine remote display app only works on iOS and Android. Sadly there is no Win8 or Winphone version.

The Raymarine remote display app is basically remote desktop (or VNC) for the plotter and gives you a second interactive display anywhere that you want it on the boat. If I'm anchored in an unusual situation I'll leave my cockpit plotter turned on and use the remote display below to keep an eye on our depth and location.
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  #23  
Old 03-05-2014
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Re: GPS Accuracy - how much is actually needed

Quote:
Originally Posted by Alex W View Post
Since the OP has a Raymarine A67 I said iOS or Android because the Raymarine remote display app only works on iOS and Android. Sadly there is no Win8 or Winphone version.

The Raymarine remote display app is basically remote desktop (or VNC) for the plotter and gives you a second interactive display anywhere that you want it on the boat. If I'm anchored in an unusual situation I'll leave my cockpit plotter turned on and use the remote display below to keep an eye on our depth and location.
Sorry, sloppy reading, I didn't realize that you were referring to proprietary repeater software. I thought you were suggesting a second, independent chartplotter on a tablet.
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  #24  
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Re: GPS Accuracy - how much is actually needed

OK, OK, I am almost convinced that chart plotters are nice. After considering the 4-5 times I have been really confused about exactly where i was I can see that a chart plotter would be nice.
Several years ago when we sailed from West End to Freeport, we wanted to go into a narrow channel east of the main Freeport channel and I just couldnt locate it with my binocs and didnt want to get in too close due to reefs. Suddenly, my daughters BF brought up his laptop to which he had a GPS connected and overlaid our track onto google earth. I was effin amazed.

So, do Ipads have built in GPS? I've never used a tablet computer.
That Lenovo Miix, does it run Win 8 or android? Could I get it with Win7 instead of Win8?

All this 21 century stuff is gonna kill me. Next they'll be putting flush toilets on boats.
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Old 03-05-2014
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Re: GPS Accuracy - how much is actually needed

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Originally Posted by Frogwatch View Post
OK, OK, I am almost convinced that chart plotters are nice. After considering the 4-5 times I have been really confused about exactly where i was I can see that a chart plotter would be nice.
Several years ago when we sailed from West End to Freeport, we wanted to go into a narrow channel east of the main Freeport channel and I just couldnt locate it with my binocs and didnt want to get in too close due to reefs. Suddenly, my daughters BF brought up his laptop to which he had a GPS connected and overlaid our track onto google earth. I was effin amazed.

So, do Ipads have built in GPS? I've never used a tablet computer.
That Lenovo Miix, does it run Win 8 or android? Could I get it with Win7 instead of Win8?

All this 21 century stuff is gonna kill me. Next they'll be putting flush toilets on boats.
I resisted chartplotters, too, I thought my Magellen 310, with nothing but Lat Lon's and a course track, and paper charts was all I ever needed. Then I bought a used center console that already had a Garmin chartplotter mounted on it (with an old black and white model screen). I have to admit, it made a believer out of me.

I now have two chartplotters on my sailboat. One just as a back up.
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  #26  
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Re: GPS Accuracy - how much is actually needed

Here's an interesting article on WAAS and GPS accuracy :

The coastguard reported real world performance for Loran-C of 50m (return to position accuracy). WAAS-enhanced GPS guarantees 7.6m, although real-world performance is considerably better. I routinely see accuracy of about 1m.

Sometimes when I record my GPS track with my handheld and paste it into Google Earth, I can see where I walked down the dock, to the restroom, and back. The accuracy looks like about 1m to me.
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  #27  
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Re: GPS Accuracy - how much is actually needed

Quote:
Originally Posted by Frogwatch View Post
So, do Ipads have built in GPS? I've never used a tablet computer.
It's my understanding that the iPads with Wifi+cellular have built in GPS, and you don't need a data plan for it to work. We bought a refurb last year, installed InavX and a few other sailing-related apps, and had no problem with it.
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  #28  
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Re: GPS Accuracy - how much is actually needed

Low-end ipads with wi-fi only don't have GPS. The higher-end ones with cellular, do. It's not that you need cellular to do GPS, just that the GPS uses the antenna in the cellular module.
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  #29  
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Re: GPS Accuracy - how much is actually needed

cthoops:

What if you are out of cell or wifi range? Do you still have GPS?
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  #30  
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Re: GPS Accuracy - how much is actually needed

Yes, the GPS function is entirely separate. But you must have the cellular module for the antenna.
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