I was fishing this is weekend and noticed on the down scan that I fished thru a ditch that was not shown on my chart with the fish n chips mode enabled. When I switched over to regular navionics it showed the ditch. I thought that fish n chips was supposed to be better than the regular. What exactly does the fish n chips mode do?

FishNChip is the setting to display SONAR CHARTS.
Sonar Charts is contour mapping layer created by sonar logs uploaded by those participating in that program. It is not Navionics data and it is not sold, it is a free service for those participating in collecting that data and for those wanting to view it. If is free with an update for Navionics Hotmaps Platinum and Navionics+ card owners. It is also viewed on the Navionics website's WEB APP and a map layer on the Mobile App.
Before anyone did any of that, most all locations got preliminary contours lines to be adjusted by those sonar logs. ONLY a location that has been recorded and uploaded will be close to accurate and only as accurate as the person doing the data recording.

You cannot assume any part of a Sonar Charts map is accurate unless you did the sonar logs yourself or verify with your sonar that the contours are accurate at a particular location.

This is a composite of a lot of sonar log tracks that I did at a particular lake. ONLY what is exactly under the red lines is accurate. Only until that satellite view is solid red will the contour map be accurate everywhere.

An example of fixing a part of the Sonar Charts mapping is this location where the map curser is.
After I did some logs and they were processed, I noticed that location was not accurate since I had not recorded it. The next time on that lake I recorded that area to fix the map.

This is what it looked like with the error:



This is the Google Earth sonar log track I did to collect the data to fix it:



This is the corrected contours for that location--notice the GPS co-ordinates in the two map views.




These examples are at the same lake as the composite sonar log track image above.

Additional note. This map is entirely a result of my sonar logs. Navionics or no other source had any contour mapping or even an outline of that lake. It is fairly new lake. I do some logging about every time I am at that lake to fill in where I have not collected data to fix those errors.
Navionics created the zero line (shoreline) and did a full lake of contours with just a few of the first logs using interpolation. I or anyone else just needs to correct all the areas that need it.
It is a 420 acre electric-only lake and it takes a long time to cover all of it to have an entire accurate contour map. I fished that a few years before the Sonar Charts program started so I know the lake quite well and can tell which areas need correcting.


As Paul Harvey would say "now you know the rest of the story"

Great info Wayne, and nice mapping on your lake!!


Bvon, can you tell me what chip you are using, the last update on the chip and also location of this issue? Welcome to PM that info if you want, I would like to check out something for you. This is not the norm for the Sonar chart layer but could be a glitch of some sort.

Another example of fixing a location with inaccurate contours at that same lake. I usually don't travel between the 6' hump and right shoreline since that is where a lot of bank beaters start fishing after leaving the ramp so I had not collected data there. All that area was interpolated from sonar logs nearby.
I was using some of the adjustments with the Mobile App and noticed the depths don't work that way since water has to flow downhill (towards the top). So I logged that area to fix it and these are the before and after results:

Before:




After:

This will show the value of the Sonar Charts program--- same lake as above.

When I first stated fishing there, this is what my Chart view showed with waypoints:



Then I used Google Earth Paths to draw the shoreline to have a reference for my waypoints. I did not realize that one waypoint was incorrect due to a digit error. Fixed that. Some of those waypoints were created with a hand held GPS unit when the lake was just filling up and I entered them manually in my sonar/GPS unit.

Thanks for the help guys. Corey I will pm you the info when I get back to the house.