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Navionics accuracy...


Thunderfoot

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I downloaded the Navionics app for my iPhone last weekend and used it for the first time on Monday night. It doesn't seem all that accurate. I was set up on 26' and according to the app I was at like 16'. Anyone else notice this? I opened google maps right after I looked at that and that app was exact for my position looking at satellite view. I still like the app as the maps seem more accurate than the DNR lake maps but I was hoping to use it as a GPS and find some features under the ice. Your thoughts?

Joe

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I marked a spot on a lake for later fishing because fishing was good and it put me 50-100 yards away from where I was sitting. I was in 20 fow and it said I was in like 10. I then tried it on another lake and again when we were in what should have been 10 fow, the map showed we were in closer to 8 and about 50 yards away again. Its a nice app, just needs to be able to be calibrated. I also noticed when looking at it last night, that it showed a church in what would have been my front yard according to my "Home Marker" and actually the church is a block away out my back door.

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I think it matters what lake your on and if it has been recorded as a high definition lake or not. Some lakes seem like they are just using the DNR map. Funny thing is on some of the high def. lakes my iphone with Navionics is more accurate than my Garmin with a Lakemaster Chip.

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I have noticed on the bigger lakes it is pretty good but some of the prairie lakes it is not good the other day i was in the middle of the lake it showed me on the shore. But it is just another tool to help.

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From my experience it is mostly accurate, i have been on a couple of lakes where the hole or hump i was looking for was not exact but it put close enough to narrow it with a couple of holes in the ice. One thing you have to remember also is the GPS as in all GPS units is only as accurate as the satelites its able to receive. 4 locked sattelites will be more accurate than 2 due to triangulation. i have used this app in fog and total darkness and it has guided me easily to a destination. Does it replace a dedicated GPS...NO does it work tremendously well for the $10-$15 ABSOLUTELY

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It seemed to be about 20 feet or so off when I used it which when you think about it isn't all that bad. I don't have any means of transportation on the ice so I walk and drag my equipment. There's a hump that I want to find on a lake that is already a half mile walk so once I get there I don't want to have to do a ton more walking to find it. I think I will be able to make it work though. I figured with my phone it would triangulate pretty accurately since I can use google maps and the marker on there showing my position is hovering over exactly where my couch is in my house! It's also handy when packing up at night with no moon to light my way. There's no lights or anything to make the access I park at readily visible at night and it's a new lake to me so having this to point me in the right direction is worth the $10 alone! Great app just wanted to get other peoples input on the accuracy. Thanks!

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Chips/apps are only as good as the reciver they are being used in... My HDS units are more accurate than my Expedition is...

+1

Cell phones were not meant to be dedicated GPS units so you will see variances sometimes. I've been on a hump with a buddy and on each phone the Navionics shows us on different sides of the hump, about 50ft apart while standing in the exact same spot. If you want consistent accuracy gotta buy a dedicated unit, but heck, can't beat $15 to get you pretty close most of the time!

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Yea like Clayton said, the lake could have dropped do to low water level. Example like Whitebear it may say 15 ft on app but your finder says 8-10 ft. As long as your gps/app position you on where you are, then you're good.

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My method to find the "perfect spot" is as follows:

1. Go to DNR site print a map, mark 5-10 spots

2. Bust out my cell phone get to said location using Navionics

3. Bust out my Garmin Etrex 30 and also go out to said location, try to find GPS coordinates with longitude and latitude.

Narrow it down using the tools on hand. And start popping some holes.

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If you are getting within 20 feet of a known spot using a GPS regardless of whether its a smartphone, handheld or dedictated large unit like HDS, or whatever that is pretty accurate.

If you look at the format for location on the app you are only going to TWO decimal places on the phone, while on a true GPS you will go to 3 or more. This allows much more accuracy in itself.

No map chip should be used as Navigation because unless it is from the government, military or some mapping company they are not able to be as precise as you would need.

If getting within 20 feet or even 100 feet of a known spot isnt good enough why bother with a GPS of any type?

Folks never had these devices 15 years ago and fish were still caught. Drill some holes and be thankful you dont have to go based on landmarks nearly as much and figure it out.

You can make cell phones more accurate by enabling GPS and Cell location services. This way it would use cell towers to triangulate and satellites.

The other thing is you cannot zoom in as far on a phone so what may appear as "your spot" may really not be it because you are at least two zoom levels higher than a handheld or large GPS unit.

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CaptainMusky....

I agree with you 100%.

GPS was first used for navigation to get you to home / landing.

If the GPS gets you to with 20-100 feet from the landing and you are not happy with that, maybe you should not be on the lake in the first place.

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I don't think he is referring to the GPS accuracy. If I take the map itself my Navionics on my cell and the map on my Lakemaster it's just not always 100% correct. Sometimes one map is better than the other.

As for referring to High Def, I considered is to be the space between contour lines. High Def would be 1ft contour lines.

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I see what you mean Lawrence, but say you drill a hole on a hump and mark it with a flag to return to that spot. You mark the spot with your GPS or smartphone. Then go across the lake and intend to come back to the spot knowing full well where it is.

Your GPS could say you are on the spot when you are a good distance away from it. Is this the map's fault or the GPS? Its the position of the GPS, not the map necessarily.

I agree the maps themselves can be terribly inaccurate, but if you are intending to return to a known spot regardless of what the map detail says, you are depending on the accuracy of the GPS, which at best is 20 feet.

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If it can bring me within 20 feet heck even 50 feet then in the grand scheme of things thats pinpoint accuracy to me. If i need help at that point to find something 20 feet away well then i need help that electronics cant give me wink

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On my Galaxy S III I have not noticed huge differences. Occasionally I could be about 10 yrd difference from what the maps show but really it's not far off at all. Water depths in lakes change too (granted not drastically) but I find a foot here and there off due to this as well. For me, the app gets me to the right location, then I drill holes and test with the humminbird. I always drill multiple holes to check depths against what I see on the map. It basically validates I'm on the right drop/point/hump.

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Format

Here is a sample how the different format reads. These are the same Latitude waypoint, you can see how they differ.

DMS reads deg, min, sec - 45deg 8min 28.2sec

DM reads deg, min - 45deg 8.470min

DD reads deg - 45.14177deg

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I never said I couldn't find what I needed at 20 ft off, which was just a guess, I just wanted to know if I was the only one experiencing this, I wasn't even complaining, at $10 what's there to complain about? I know a lot of lakes are low but as far as depth the app said 16' and vex said 26', that seemed pretty drastic. It's a fairly steep drop but it just seemed to be a lot. Comparing the navionics map to the DNR map it seems accurate, I think it was just my phone. I have no experience with GPS, unless it's in a car, so it's fairly new to me. Yes I am a novice angler and if you don't think I belong out there that's fine, won't slow me down a bit.

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If it can bring me within 20 feet heck even 50 feet then in the grand scheme of things thats pinpoint accuracy to me. If i need help at that point to find something 20 feet away well then i need help that electronics cant give me wink

When I was in Eagan after Christmas, I marked a spot on my Navionics app and it showed I was on a point when in reality, I was 50 to 100 yards from the point. According to the way point, I was in 15 fow instead of 20.

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