Navionics app (Android & iOS)?

[Rebeleye]

Got a question for anyone that uses Navionics app on their mobile device. While fishing Mazaska (near Faribault) on Saturday, we noticed that the depths were not matching between our phones and where we were. Often times it was 15+ feet off. I was using a Droid Razr M and my brother in law had an iPhone 4. Both phones were giving the same depths the entire time.

So, is it a bad survey job of that particular lake? Or, could it be something else? Note: Both phones were updated with latest OS and the apps were updated as well.

Thanks!

[DTro]

Yes, some lakes are much better than others. I suspect its just that lake in your case.

[expl]

I can tell you there is a great difference in contours and depths between the Navionics app and the Lakemaster chip as I have been useing and comparing both,at times I dont know which one to believe.

[Wolffy]

I have not found a local lake that matches the navonics app. All depths are + or - up to 5' off. I have not found any of the breaks to be even similar to what the app has listed. I haven't even found a spot where the depth was the same on the app. I'm using the galaxy s4 and so far do not think this app was worth it when there's a free one out there that gives better contours.

I was on big stone this weekend and even on that lake the depth wasnt that close. Perch were really slow so we tried to find some holes and couldn't do it with the app.

Correction. Looked up the other app I had that was free now the lake maps are $29.99 a year.

[Rebeleye]

Thanks all. It sounds like you get what you pay for with these apps. I have an older Garmin Nuvi that I'm having thoughts about pairing up with a Garmin LakeMaster chip. Might do the trick as a poor mans GPS unit.

[fisherman-andy]

Navionics: Advanced Map Options allows you to control the display of your map including:

Shallow Area.

Depth Shading indicating a depth range.

Depth Contours filtering bathymetry to customize your view.

Water Level adjusting for tide or lake level fluctuations: spot soundings and shorelines automatically update.

Seabed Areas displaying bottom composition detail (available in select areas).

Fishing Mode to set Fishing Range to indicate key fishing areas.

* This is a paid add on feature and must be purchased within the app itself. Also look at the Navionics+ upgrade subscription thar features more detailed lake contours, depths.

[CAMAN]

Navionics can't possibly survey every lake in the state let alone country. Instead, for the lakes they have not surveyed yet they use dnr and other supplied maps that could be 60+ years old. They can be 30+ feet different than the actual depth.

The lakes I have been on that navionics has actually surveyed with 1 foot contours has been pretty dang close. They aren't always perfect but they can usually get you close enough to find what you're looking for. Plus remember you are using a phone's GPS, they aren't designed to be the most accurate, the average user wouldn't need closer than 10-20 foot accuracy.

[Rebeleye]

Navionics can't possibly survey every lake in the state let alone country. Instead, for the lakes they have not surveyed yet they use dnr and other supplied maps that could be 60+ years old. They can be 30+ feet different than the actual depth.

The lakes I have been on that navionics has actually surveyed with 1 foot contours has been pretty dang close. They aren't always perfect but they can usually get you close enough to find what you're looking for. Plus remember you are using a phone's GPS, they aren't designed to be the most accurate, the average user wouldn't need closer than 10-20 foot accuracy.

CAMAN, I agree that Navionics can't possibly survey every body of water. However, I don't see how Navionics can say they're offering a solid product if they're using old DNR maps from 60+ years ago. Yes, there is a disclaimer before you use/open the app. I guess my thought is, if Navionics hasn't truly recently surveyed the lake, they shouldn't be providing inaccurate information, and possibly be putting people in harms way.

[Big A]

Navionics: Advanced Map Options allows you to control the display of your map including:

Shallow Area.

Depth Shading indicating a depth range.

Depth Contours filtering bathymetry to customize your view.

Water Level adjusting for tide or lake level fluctuations: spot soundings and shorelines automatically update.

Seabed Areas displaying bottom composition detail (available in select areas).

Fishing Mode to set Fishing Range to indicate key fishing areas.

* This is a paid add on feature and must be purchased within the app itself. Also look at the Navionics+ upgrade subscription thar features more detailed lake contours, depths.

SWEET!! Thanks for the Tip! I love this app and use it all the time. works great.

[SDS]

Its not fair to compare Navionics to the Lakemaster Chips in my opinion because of the lack of detail and accuracy. The Navionics app is nice for getting an idea of the lake and quick refeance. The Lakemaster Chip has been 100 times more accurate than the Navionics app. Lakemasters helps to find spot-on-spot locations and the finest details. Lakemasters will also not be 100% accurate for every inch of the lake but still is many teirs above the Navionics app.

Both serve a good purpose and I use both just depends on what im trying to do.

Of course we are all have opinions.

[Fred_Bear]

Its not fair to compare Navionics to the Lakemaster Chips in my opinion because of the lack of detail and accuracy. The Navionics app is nice for getting an idea of the lake and quick refeance. The Lakemaster Chip has been 100 times more accurate than the Navionics app. Lakemasters helps to find spot-on-spot locations and the finest details. Lakemasters will also not be 100% accurate for every inch of the lake but still is many teirs above the Navionics app.

Both serve a good purpose and I use both just depends on what im trying to do.

Of course we are all have opinions.

Great post, took the words right out of my mouth!

I have and use both Lakemaster and the Navionics App.

[cribbageboy]

A buddy and myself had the same problem on Mazaska on Saturday. It was consistently 5 or so feet off. Must be a bad survey on that lake. I have used it so many times and never had a problem, that I actually didn't believe the flasher. Had to dig out the old fashion depth check to verify. lol.

[Raider4ever]

Your phone is nowhere near as accurate as the GPS unit in your FF. I have it on my iphone 5 (with the latest updates in both iOS and app). Had it on a lake in GR MN (with 1' contours) last fall and it was pretty darn close. It got me to the structure I wanted without fail. On my cabin lake in WI it's not as accurate but it's darn close. Is it going to replace your $500-$1200 FF? No of course not. Is it going to put you on that 3' wide "spot within a spot"? No of course not. Would I use it to barrel-arse through a new lake based on what this app tells you, thinking "Well it says there aren't any rocks."? No of course not. But if you are on an unfamiliar lake (or familiar one for that matter) and need to find some starting points, for $10.00 it's hard to beat. If you're biggest complaint is that your $10.00 chart of the United States isn't perfect, lucky you!!!

[CAMAN]

CAMAN, I agree that Navionics can't possibly survey every body of water. However, I don't see how Navionics can say they're offering a solid product if they're using old DNR maps from 60+ years ago. Yes, there is a disclaimer before you use/open the app. I guess my thought is, if Navionics hasn't truly recently surveyed the lake, they shouldn't be providing inaccurate information, and possibly be putting people in harms way.

I haven't bought a Lakemaster product in about 4 or 5 years now but the last time I checked it out they did the same exact thing....

[JoeTC]

Not sure how anyone could expect this to be more accurate than +\-5ft. Lakes can fluctuate a few feet or more, and how far down is your transducer? That's up to five feet right there plus you using a phone gps that could easily be 30' or more off which will really throw things off, especially if you're on a break.

I think it's a great tool and gets me close to the structure I hope to fish. From there you still need to drill some holes and check them with your flasher. It's pretty easy to tell if a lake was surveyed or if it's a dnr overlay. With dnr maps you are obviously going to be way off on the gps but it still gives you the general lay of the lake which gives you a good starting point at least and by no means puts anyone in harms way.

People spend hundreds if not thousands for lake mapping systems on their boats and with handhelds so I think what you get for $15 with this app is a pretty good value.

Joe

[aquafang]

I use the south dakota game fish and parks guide -pocket ranger app. It does not give lake contours but it uses google maps i think and it lets u mark waypoints. Pretty handy for marking spots. And its free.

[Rebeleye]

Not sure how anyone could expect this to be more accurate than +\-5ft. Lakes can fluctuate a few feet or more, and how far down is your transducer? That's up to five feet right there plus you using a phone gps that could easily be 30' or more off which will really throw things off, especially if you're on a break.

I think it's a great tool and gets me close to the structure I hope to fish. From there you still need to drill some holes and check them with your flasher. It's pretty easy to tell if a lake was surveyed or if it's a dnr overlay. With dnr maps you are obviously going to be way off on the gps but it still gives you the general lay of the lake which gives you a good starting point at least and by no means puts anyone in harms way.

People spend hundreds if not thousands for lake mapping systems on their boats and with handhelds so I think what you get for $15 with this app is a pretty good value.

Joe

I never realized until now how far off cellular GPS can be. You're right Joe, these apps really are just designed to put you closer to your ideal fishing spot. Thanks

[graf703]

That's up to five feet right there plus you using a phone gps that could easily be 30' or more off which will really throw things off, especially if you're on a break.

Joe

My understanding from previous disucssion is that the phone gps is just as accurate. I consider my phone to be way superior than my old garmin.

[centralmnguy]

Try downloading a smaller map area (just the lake or lakes you fish)...I know when I first downloaded mine on my phone I did the entire state & it was missing alot of info/contours etc. & took up alot of data/memory.

IMO-lakemaster is more detailed & accurate but its nice to have both to go off of & pinpoint your location. & if your handheld is anything like mine it eats through batteries very fast.

[V-12 Merlin]

Try downloading a smaller map area (just the lake or lakes you fish)...I know when I first downloaded mine on my phone I did the entire state & it was missing alot of info/contours etc. & took up alot of data/memory.

IMO-lakemaster is more detailed & accurate but its nice to have both to go off of & pinpoint your location. & if your handheld is anything like mine it eats through batteries very fast.

That's a good tip. I bought the Navionics app this fall and am anxious to try it. I figured for the money, it was worth a try.

One thing I was wondering is if the iPhone "GPS" uses the cell towers for triangulation to get the phone's location. If it does, then the accuracy could vary widely, depending on cell reception and tower location.

On the other hand, actual GPS receivers use satellites for triangulation, and the accuracy would be more dependent on the quality of the receiver, rather than location of the satellites.

That may explain why some people seem to have rather poor luck getting the depths right when using a cell phone, compared to a GPS receiver. I also think the different map companies can have some lakes mapped better than others, which probably accounts for the other main reason.

[aanderud]

My understanding from previous disucssion is that the phone gps is just as accurate. I consider my phone to be way superior than my old garmin.

Phone GPS position is nowhere near as accurate as a handheld. The phone version of the navionics app won't even zoom in far enough for you to see the difference, but if you've ever tried using a phone for geocaching you'll believe me.

[aanderud]

One thing I was wondering is if the iPhone "GPS" uses the cell towers for triangulation to get the phone's location. If it does, then the accuracy could vary widely, depending on cell reception and tower location.

On the other hand, actual GPS receivers use satellites for triangulation, and the accuracy would be more dependent on the quality of the receiver, rather than location of the satellites.

The mapping apps don't just use cell tower triangulation. Phones have all had GPS chips in them (required by law) for about a decade now.

[Savage Brewer]

Ok lets address the real issue here first.

GPS accuracy.

Most phones use A-GPS (assisted gps) and do not support WAAS (This includes all models of iPhone, and all Android phones that I am aware of).

This means that the phone uses the cell phone towers to get a rough fix until GPS triangulation can happen.

This means at first the accuracy may be off by up to 100 meters in any direction until the phone locks.

Once standard GPS locks, the device will have an accuracy of roughly 10 meters radius(meaning it can be off by 33 feet in any direction).

In most modern phone GPS accuracy is probably closer to 5 meters radius.

In order to achieve better accuracy you need two things, more simultaneous satellites to calculate off of and WAAS.

Most phones may lock onto more than 3 satellites but they can only calculate position off of 3 at a time.

Commercial GPS receivers, Garmin handhelds and our newer chartplotters (lowrance and humminbird) can lock onto up to 12 satellites at a time and calculate position off of 5 or more of them at a time and also use WAAS.

So you ask what the deal is with this WAAS, basically it is a way to provide accuracy down to 1 meter. Solar activity and doppler shift can cause problems with the signal we receive. Doppler shift occurs when a RF signal hits the atmosphere at an angle which causes the frequency to shift and bend for lack of simpler terms.

WAAS uses multiple ground stations at specific locations that read the offset variations of the GPS signals received here on land, then it re-transmits the data to two satellites so WAAS capable receivers can use that data to become extremely accurate.

To test this a person can do it more easily in the summer, set your boat chartplotter, a handheld gps or two, and a couple different phones. Go to a parking lot and set all of them to display the current latitude and longitude in the same format. You will then be able to watch the gps drift a bit and also you will probably notice that they will all show a different location.

So, how do we fix this, well either accept that you magical smartphone is probably not the most accurate navigation device. Or a person could look into an external Bluetooth GPS receiver with WAAS, this will provide better position details and save battery as the internal GPS pulls alot of power.

Another thing is remember how the lake levels can change.

So say at a given spot, the normal depth is 20 feet.

The Navionics mapping occurs during a wet cycle and that spot reads 22 feet at that time.

Now we ware on the same lake during a dry year and the lake is down 2 feet from normal (18 feet).

So with correct offset the current depth is 4 feet different than the maps.

And now to top it off, the ice is 15" thick and you put the transducer bottom 3" below the ice to get a clean shot.

Now your flasher will be reading 15.5 feet deep.

So here is another way that the lake map will show that it is supposed to be almost 6 to 7 feet deeper than your flasher.

My recommendation is that the Navionics app is a great tool to get you in a general area, but then trust your depthfinder to tell you whats going on down there right now.

[Savage Brewer]

I actually am considering either the Garmin GLO or GlobalSat BT-359 external Bluetooth GPS receiver to help my phone with accuracy issues when geocaching with my phone.

[CAMAN]

Excellent Information Savage!