how accurate are navionics topo maps 2024
Insanity reply :
Before i buy the sd card for my fish finder i been playing with there mobile app looking at a place I just fished last month. And it's pretty far off a couple of areas. The water drops far faster in some places then it shows.
At another place I can see sticks and logs sticking out of the water where it says there's 11 ft of water at summer pool. Theres at best three ft.
Im assuming there mobile app is just like all other apps and just crap.
So is there card worth the money? Or are they the same maps?
Wayne P. reply :
You have to use some common sense when using mapping.
Maps are created at a certain water level, when the water level is not at that point, the depths cannot be the same.
The Navionics Mobile App, their website's Web App, and their map cards have the exact same maps if updated the same day.
The Navionics Mobile App has a water level offset setting, use it to adjust the lake level to the current conditions.
Most sonar/GPS units do not have that adjustment using Navionics or another digital map product, again use common sense.
If you have a Humminbird unit and your water of interest is covered by Lakemaster mapping in HD, then you would have the lake level offset choice with that product.
Wayne P. reply :
Additional comment.
Every digital mapping product has locations that are done by their own survey team, and they have maps that they purchase from other sources to have more content in their mapping products. ONLY the locations that they do themselves will be the most accurate. Locations on the map products that are their surveys are typically identified as HD.
Additionally no mapping company collects data for every square foot of terrain. Contour lines between surveyed data points are filled in (interpolated) either using software or manually. It is up to the user of those map products to confirm the accuracy of the data with their sonar.
Insanity reply :
My point was even at flood stage the water can't get to 11 ft at the one spot it showed. It doesn't exist ever. The other is steper then it showed.
However I noticed after I posted. I was using a link someone gave to there site direct to a map you could use. There pay app my be much better.
It's for a Larance.
Next question can yo use the sd card in a lap top to see and maybe set way points from home.
Wayne P. reply :
No unless you purchase a software that can read a map card. Navionics used to have a software that would ---NavPlanner II
Garmin has one for their map products. Lowrance may have one that works with their Insite maps.
Waypoints are GPS data and mapping is not GPS data. You can have waypoints without any map product.
I had about 75 waypoints for this lake and there was no contour mapping for it at the time:
I later surveyed it myself to collect the data to have a HD contour map for it using Navionics Sonar Charts. It looked like this after many hours of collecting data:
There are incorrect contours at all the places I did not pass directly over. I fix those errors as I take the time to do more data collection if a particular location would be better represented by more accurate data.
IntroC reply :
The Navionics app I have for my phone is horrendous.
Insanity reply :
On 12/26/2015 at 11:21 AM, IntroC said:The Navionics app I have for my phone is horrendous.
I just bought it. (Before i seen your post.) It has the same mistakes as the free Web app. That's what I was viewing earlier the Web app.
Anyway I can get more then my money's worth from it on just the satellite view of the land. I'm always using Google Earth. Hump now the areas im enterested in are downloaded permently to my SD card on my phone. Hopefully some of the water is correct. Most of the areas Ive been fishing are impoundments that arnt covered. So I can't tell more till I put the boat on some new spots.
FloridaFishinFool reply :
On 12/26/2015 at 7:51 AM, Wayne P. said:Additional comment.
Every digital mapping product has locations that are done by their own survey team, and they have maps that they purchase from other sources to have more content in their mapping products. ONLY the locations that they do themselves will be the most accurate.
A lot of the paid for bathymetric maps are done by satellite imaging.
The state of Florida has various government agencies at the state level, county level, even city and town level who produce their own bathymetric maps from direct surveys of the lakes and then combine that info with satellite image info to produce some really accurate maps that I can download for free from the various government agencies.
When I compare the bathymetric maps made by government agencies and then compare it to satellite only made maps I find huge discrepancies. For example, in Kingsley lake is a second deep hole. It is clearly shown on man-made maps, but the satellite maps I have seen do not even show that second hole.
Lake Maitland is another one with a nice deep hole shown on man-made government maps, but the satellite maps I have seen have again completely missed the hole all together.
And as stated above, the contour lines from man-made maps can be different than those from satellite only imaging.
How can satellite-only generated maps be accurate when as stated above on well known lakes like Kingsley and Lake Maitland even be considered as "accurate" when they completely miss known holes and don't even show them? That is NOT accurate. That is hit and miss.
Point is, for me here in Florida, I don't even use satellite made maps. I have downloaded hundreds of maps for this state from numerous government agencies and find that for my purposes they are accurate.
One of the lake programs I follow here in Florida called Lakewatch shows on their website how they make the really accurate maps:
http://lakewatch.ifas.ufl.edu/MapList.htm
Satellite-only mapping is not as accurate. Not even close in some instances...
One day satellites may be able to look through the water and produce some accurate 3D images, but technology is not there yet.
KirtH reply :
I will comment on this. If you can find lake mapping that is 100% on every body of in the US please share it with me. I find Navionics with SonarChart to be the most accurate a higher percentage of the time, I use Insight mapping and will compare the 2 and Navionics with SonarChart to be far more accurate and up to date. Yes there are lakes that may not be perfect and I think you will find that among all lake maps. Just to make sure are you looking at the SonarChart layer? There is a huge difference at times between the Nautical chart layer and the SonarChart layer. What Navionics map card are you using? When on the mobile or web app are you looking at the SonarChart layer? Be sure to click on the sonar icon and toggle it on. Water level fluctuations cannot be factored in when creating maps, they use a or normal pool level when creating mapping.
One option depending on sonar you have is to do some SonarChart Live mapping with your sonar and mobile app. for the most exact detail.
FloridaFishinFool reply :
I forgot to mention that another reason I go to government agencies for most of the maps I use is because satellite generated maps never show bottom structure locations.
The Florida FWC has a new program of "planting" plastic trees on lake bottoms all across Florida to improve fish density by giving them artificial cover. They started this new testing program in Lake Griffin.
I want to know where these artificial trees are being planted all across Florida. Satellite map companies will never give me that information. But the FWC does give it to me for free since our tax dollars have already paid for it!
Here is a link to Florida's interactive fish attractor map for the statewide program:
http://atoll.floridamarine.org/fishAttractor/
Here is the PDF list link:
http://myfwc.com/media/2686794/fw_fishattractorlist.pdf
Once I collect this data it can be programmed into GPS and also be added visually to edited digital maps I have archived.
Fish attractors being installed in Lake Griffin
Posted: Tuesday, February 18, 2014 6:00 am
Austin Fuller | Staff Writer austin.fuller@dailycommercial.com | 0 comments
The first large-scale, comprehensive evaluation by the Florida Fish and Wildlife Conservation Commission of artificial, recycled plastic fish attractors in Florida is beginning in Lake Griffin.
According to Florida Fish and Wildlife fisheries biologist Brandon Thompson, the attractors are being assembled and taken into the lake from Leesburg’s Herlong Park.
Thompson said there will be 18 quarter-acre sites in the lake, with 100 structures in each site. Twelve of those sites are regular brush attractors that already have been deployed, while six of those are the recycled plastic attractors.
Thompson said the usual oak brush attractors start to lose their complexity after three to five years, while the plastic attractors could last for 10 to 20 years.
The brush attractors were placed several weeks ago, and Thompson expects to be finished putting in the recycled plastic attractors by next week.
The attractors will be both for research and to help concentrate fish for fishermen. Thompson said in areas that are not over-harvested, the Florida Fish and Wildlife Commission wants to help people catch fish.
“Sometimes people view the FWC as putting in regulations to limit people, but really we work for the anglers and we want to see the highest populations of fish; we want to see them catching the most fish,” he said.
Thompson said any offshore structures and cover help attract fish, and more complex structures attract more fish.
“There’s gonna be a lot of different stuff growing on these, similar to how there would be on oak trees, that attracts the bait fish all the way up the food chain,” Thompson said.
Thompson added there are short- and long-term goals for the project, with an initial goal being to see how the plastic attractors compete with brush attractors in concentrating fish, and a long-term goal of seeing how the plastic attractors compete with brush once brush starts to break down.
Twelve members of the Hawthorne Fishing Club volunteered to put together the artificial attractors on Monday.
“I think it’s really, really important to involve the stakeholders, the people that are going to take advantage of these attractors and the people that are gonna be out there catching the fish on them,” Thompson said.
Bill Connelly, a member of the fishing club, said the group of fishermen wanted to do what they could to help Fish and Wildlife improve fishing and the lakes.
The artificial attractors have 30 limbs on each.
The plastic attractors have been used in other states and, from what Thompson has seen of those results, they look promising, he said.
Wayne P. reply :
On 12/26/2015 at 11:28 PM, KirtH said:I will comment on this. If you can find lake mapping that is 100% on every body of in the US please share it with me. I find Navionics with SonarChart to be the most accurate a higher percentage of the time, I use Insight mapping and will compare the 2 and Navionics with SonarChart to be far more accurate and up to date. Yes there are lakes that may not be perfect and I think you will find that among all lake maps. Just to make sure are you looking at the SonarChart layer? There is a huge difference at times between the Nautical chart layer and the SonarChart layer. What Navionics map card are you using? When on the mobile or web app are you looking at the SonarChart layer? Be sure to click on the sonar icon and toggle it on. Water level fluctuations cannot be factored in when creating maps, they use a or normal pool level when creating mapping.
One option depending on sonar you have is to do some SonarChart Live mapping with your sonar and mobile app. for the most exact detail.
When using the Sonar Charts map layer, you need to verify if the contours are user generated or pre-Sonar Chart data with your sonar.
Just like any other map product, only the bottom contours will be accurate where depth and location data was collected.
Most all bodies of water got preliminary contour lines when that program started. Those lines were created to be adjusted by uploaded sonar logs.
If you did not supply that data and know what areas are accurate, you should not assume any part of those maps are accurate.
This is a composite of sonar log tracks that was used to create the Sonar Chart map I posted above. ONLY what is exactly under those red lines is accurate. All other parts of any of the contour lines are interpolated (fake). Only when that lake is solid red from sonar log tracks will the entire lake map be accurate.
Wayne P. reply :
Additional info about Sonar Charts to show why you need to verify with your sonar if any mapping is accurate.
This is the same lake as above.
This location indicated by the map curser has a 30'+ depth error that was interpolated from nearby sonar logs:
After the map was generated, I saw what needed to be corrected and did this sonar log track:
This was the fix as the result of the sonar log track. Note the waypoint coordinates at the top left of both map examples:
FloridaFishinFool reply :
Wayne, your maps show a lot more details than what I find on the Navionics webapp.
Would you please post some map images of a Florida lake Maitland in Orange County (Winter Park) and post what your maps "see" around the Isle of Sicily for deep holes and bottom contour? Or, Kingsley Lake in Clay County?
I'd be curious to see the difference from the webapp I am looking at. Thanks in advance if you can post the bathymetry images...
Wayne P. reply :
That map I did is on the Web App and Mobile App and my map cards. I check the Web App to verify that my data has been processed before I do an update.
You know where those locations are, you can look at the Web App to see what is current. The Web App looks the same to anyone that views it.
If no one has supplied any data for your locations, it is what it is. You can fix it yourself if you care to.
FloridaFishinFool reply :
I think your maps show more detail and I was wondering if this might be the difference between what Navionics provides for free with limited detail and a paid for amount of detail that might be better than the webapp I looked at, but I will show what I found anyways...
Here is a government made map of a portion of Kingsley lake using sonar- made by humans on the water. It very clearly shows 2 distinct deep holes. Very clear in the image below.
But if I relied on the Navionics webapp info posted on their website, I see this image below, and it does not show the second deep hole. Maybe I don't have the Navionics set up correctly, but this is as good as it gets for me with the free non-paid webapp info I accessed off their website.
Another example is Lake Maitland. The sonar produced maps show a lot of detail:
Now look at the Navionics webapp map I see online:
No comparison really.
Same thing in the best part of this lake:
The above image is DEP produced. It is very accurate. Now take a look at what Navionics shows me of this same area:
The deep hole locations are just not shown the same. The Navionics mapping completely misses some of the holes and does not show contour bottom details anywhere close to reality based on more accurate government maps.
Is it possible to get the same level of detail as Wayne's maps show without paying for the Navionics chip or maps? I'd like to see if paying Navionics produces better quality, with higher accuracy and more detail.
Wayne P. reply :
Pay attention !!!!!!!!!!!!
The Web App has the CURRENT maps for both the Navionics maps (Nautical Charts) and Sonar Charts (user generated maps).
If you have the Mobile App and have updated it recently, it would have the exact same data as the Web App.
If detail you want is not there, it won't be there no matter where or when you look or if someone in China looks at those locations. Your examples are maps purchased from "other sources" and are NOT Navionics created maps.
Navionics adds about 2000 edits per day "somewhere" around the world.
The lakes you are interested in are not the same as the ones I fish and navigate on. Every single location is different.
The Navionics published map for this location was a scanned paper map. There was no other map and Navionics would probably never survey there. I and maybe some others uploaded sonar logs to get a better map in HD with the Sonar Charts program.
This is the original scanned paper map that shows an island that is not an island, it is a submerged hump:
This is the result of those sonar logs:
In that example, Navionics had no part in collecting the data to create the HD contours. They processed the sonar logs that were uploaded to their map server as a FREE service. That HD map is NOT Navionics data and you cannot purchase it. It is FREE.
Ohio Archer reply :
FloridaFishinFool, I have the Navionics mobile app and it shows your two lakes with much more detail although the second hole you referred to and is shown in the DEP images not there. There is a big gap between depth lines that could hold that hole. On Lake Kingsley, there is a ledge where the "30" is shown below the "65". It is almost a straight drop, not the slope on your picture. The Navionics map of Maitland also shows more detail.
But I have "Sonarchart" selected, not "Navionics" under the little sonar symbol. Under the sonar symbol there are three choices...Gov't Chart, Navionics and Sonarchart. Select whichever one gives you more detail.
I don't have the Lakemaster card for the SE so I can't tell you what it looks like.
Insanity reply :
Great info guys.
And Il have to eat crow on the hole i said i didn't think existed. I ask someone that would no today. He said there was a pond there before they flooded it. Duh I never thought of a pond.
Yea I said flooded you should see the road beds, bridges, culverts, creek channels and such. And yea lots of holes/ponds. Thinking these two lakes should be mapped to the hilt because it used to just be two rivers and dry land. Aka Land Between the Lakes ky and barkey lake.
Wayne P. reply :
The Web App has the exact same maps as the Mobile App for Nautical Charts and Sonar Charts. It is up-to-date as of the day Navionics closed for Christmas.
To check Lakemaster coverage, download the .pdf lakelist from the Humminbird Lakemaster website.
THIS is the Sonar Charts map on the Web App that anyone in the world can view if they will just look. You change the map views by clicking on the circle at the lower left of the panel.
Ohio Archer reply :
That is what I see as well. Looks like a sinkhole that got stopped up. Or an old quarry pit. FL has a lot of these almost perfectly round lakes.
Wayne P. reply :
On 12/27/2015 at 9:37 AM, Ohio Archer said:That is what I see as well. Looks like a sinkhole that got stopped up. Or an old quarry pit. FL has a lot of these almost perfectly round lakes.
The Mobile App has seven Community Edits around the lake. One is titled "Camp Blanding Ramp".
Ohio Archer reply :
I see that. So someone has been sending in updates. There are several lakes around here in SW Ohio with updates as well. As long as the people sending in updates are as thorough as you when you create your maps, these maps will only get better. But then again if someone found "honey holes" that no one else is aware maybe they wouldn't be submitted. 
Wayne P. reply :
I think in some cases the ones doing the edits do not know their notes are being shared.
RAMBLER reply :
Here, in Florida, it is almost impossible to have accurate maps of bodies of water. The weather changes so much. We have had a year or two that was so hot and dry that many of the small lakes got so low there was no (and I mean none) water at any access point. Then, it started raining and now the water on these lakes is waaaay out in the woods and up in peoples yards. Now, at what level was that map/chart made? There is no way of knowing. I use mine simply to show me where the deeper spots and contour lines are, not as an accurate depth. One lake in particular shows the deepest hole is 9'. Right now that hole is 13' deep.
Now, I talked to a Lorwrance dealer and asked how any of these lakes could all be charted. Some of them were charted by him. He was provided with a recorder on his boat. It recorded the depth of every piece of water he fished and he fished a lot, as will any pro. Now, if he, by some chance missed a small, deep hole it just will not be shown. So be it. You have to understand that to make an accurate map of a lake you have to criss-cross that entire lake in a grid pattern. Who is going to pay the price for that. Be really glad you have what you have.
You could go back to the old depth finders we had when I was a kid. You put the oar over the side of the boat and if you touched bottom, it was shallow, if you didn't, it was deep.
FloridaFishinFool reply :
I agree as far as depth goes. It does fluctuate. But for bodies of water that do not experience the effects of river current, the shape or contour of the bottom can remain consistent for decades.
I still use sonar created maps going back to the 1960's and still find them to be generally accurate.
Rambler said the above quote: " You have to understand that to make an accurate map of a lake you have to criss-cross that entire lake in a grid pattern. Who is going to pay the price for that."
And this was my whole point to my comments above.
Here in Florida we do have someone who pays for accurate lake mapping and they have been my source for more accurate maps for decades. Paid for by the taxpayers. And since the taxpayers are footing the bill, we have access to that public information which I have been accessing for decades. I have no need for any satellite generated mapping. None whatsoever. I don't consider it accurate enough to be of much value to me or my fishing activities.
Florida has 5,444 lakes, not including smaller bodies of water.
The government has a huge interest in keeping a watchful eye on these bodies of water since a lot of our drinking water is directly tied to proper care of all our bodies of water here in Florida. So the government is spending our tax dollars to accurately examine and document more and more of our lakes.
Here is a link to the Florida wateratlas website which describes the method of lake mapping they use. And Rambler, notice that they are mapping by following a grid on each lake mapped. You and I have free access to this already paid for information!
As you said in your comment above, the most accurate method of lake mapping is done by humans on the lake, not satellites. My whole point to all my comments above rests right there.
When they combine the on site grid mapping with satellite, is when we get the best info on a lake in my opinion, but satellite on its own is to me not very accurate and not very useful.
http://www.lake.wateratlas.usf.edu/shared/learnmore.asp?toolsection=lm_bathymetric
"A Bathymetric Map is similar to a contour map. In making a bathymetric map a SONAR depth finder is used along with a Global Positioning System (DGPS). Researchers map a course around the perimeter of a lake and then navigate parallel transects using the depth finder to store various depths of the lake in a consistent pattern. This data is then used to create a map showing the contour of the bottom of the lake. Florida LAKEWATCH, at the University of Florida's Department of Fisheries and Aquatic Sciences, may also provide data."
The great work our various government agencies is doing to map our Florida lakes in person using sonar is already paid for by tax payers. Once the data is collected it is free for us to access.
I have no need to pay Navionics for what they do.
Thanks for helping to make my point Rambler!
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JayKumar reply :
Many historic depth charts -- historic meaning been around for a while -- aren't accurate, as we're all finding out. This is why mapping companies are mapping the lakes with the increasingly better sonar, and while one or two are trying to get fishermen to do that for them.
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