SonarChart questions

CaptButchCaptButch Posts: 10 Greenhorn
I just got my new Humminbird Helix 7 and it came with the Navionics + card. I'm trying to learn how to use the SonarChart feature to map my local lake but not having much luck getting the charts looking good. Anybody have any suggestions on how to effectively map a small lake? Not much info on the Navionics site.


  • mikenavmikenav Posts: 696 Officer
    Hey Butch, I answered you part way in the other post on this forum, but there's a little more information in this post, so I'll give it another shot. And you're right, the Navionics site is woefully unhelpful on this subject. Sorry about that.

    From what it sounds like, you are already recording sonar logs, you just aren't getting the results you want. Are you recording using the Helix 7, saving it to your micro sd card and then uploading through the Navionics website? Or are you pairing your Helix with the Navionics Boating app on your phone and doing it live?

    Also, and this is what I mentioned in the other post, could it be a case of going too fast and maybe not getting as much data a possible? Or is there is a setting which might need to be tweaked in order to get the contours to show up in more density?

    Let me know what you've got going on and we'll figure it out.


  • CaptButchCaptButch Posts: 10 Greenhorn
    Thanks for replying Mike.

    I am using the Helix as well as a Humminbird 385C and uploading from the SD card. I'm using a jon boat and trolling motor so I doubt if I'm going too fast, usually 3 mph or less. I haven't seen any articles about tweaking my units for better density so I would imagine I need some help there. I was under the impression that the sonar logs only contained depth and GPS info.

    I'm looking at the charts using webApp as well as on the helix.

    I also had another question, Is there any way I can get the boundaries of the lake to show up more accurate? I'm trying to map a small 55 acre private lake so the current boundaries are pretty poor.

    thanks again
  • mikenavmikenav Posts: 696 Officer
    The sonar logs that you download from your unit actually contain a ton of data, one of the most important is the timestamp. When they are uploaded, Navionics runs them through this crazy long algorithm that takes into account tides at the time of the scan and a bunch of other things before they develop the contour lines on your chart.

    Speaking of of the problems I've been running into is sometimes the units are set up for low density of the actual sonar charts. Instead of showing you every single contour line, it shows you every few. Some people like this because in areas where they are steep drops, their screen can get pretty black. I know my Raymarine has a setting where I can decide if I want low, medium or high density chart detail. Maybe the Humminbirds do too?

    As for the 55-acre lake...which it sounds like you already mapped. What is the problem with the boundaries? Is it showing them as too smooth? Not jagged enough like in real life?
  • Skinny RunningSkinny Running Posts: 66 Greenhorn
    How does a time stamp work? If it's tied to the time setting on the gps my uploads are wrong? If I reset my gps (which happens sometimes) the time it defaults to when it starts back up is a different zone and needs to be corrected by several hours. Sometimes I just don't change it because I don't really care about it much. I have a phone and watch with the correct time. If it's not set right to the correct local time the contours received back are drawn with the wrong tide assumption? Also, my rig is set with a -1 offset. How does it take that into account? Sometimes I record idling along and sometimes I'm not idling and that could be about a 1' difference at the same spot depending on speed. Not a big deal for most but for where I go, it makes a difference. Are you supposed to not use an offset?
  • CaptButchCaptButch Posts: 10 Greenhorn
    No, the lake outline shown on the navionics chart is not even close to the actual lake and missing a lot of the lake area. I overlay it on the google earth map and it's way off. It's Lake Francis in Central FL just a little SW of Lake Eustis. I've attached a picture of the lake with the areas that need to be included marked in yellow. As you can see, it's a lot of the lake that's not included in the charts and a large area at the south end that used to be lily pads is missing.

    Does tweaking my density on my unit before making my logs affect the charts? and does it matter if I have the RTS window open or not?
  • mikenavmikenav Posts: 696 Officer
    I had to go to the experts for that last question. Here is what I got back: No prob, about the offset and time, doesn’t matter what the user has in there. The log itself contains the GMT and offset values. Navionics uses the raw data and calculates its own. For lakes time won’t matter anyway.

    Density won’t affect logs at all (other than you being able to see them on your screen). Essentially, none of any user settings changing the display will affect the logs, we get all raw data.

    As for the lake image, this is from the app on my phone. It looks like the Navionics procedure corrected the shoreline and added in the sonar charts.
  • CaptButchCaptButch Posts: 10 Greenhorn
    It looks real good there but using webapp or on my unit the outline look like the picture i sent. What you are seeing is google earth with the sonar charts, it doesn't look anything like that on my unit or on webapp. It looks like when the border was drawn for the charts, none of the green area around the lake was seen as lake but most of it is lily pads and tree overhang.

    I know my little lake is too small and insignificant for Navionics to take the time and effort to fix the border so I thought there might be a way to fix it myself. I assume there is not, correct?
  • mikenavmikenav Posts: 696 Officer
    I can see what you're saying. The shoreline looks a little jagged on the webapp.

    They can fix it. And they will. Let me send them the coordinates of the lake (since I know where it is now) and I will relay them the issue with the webapp and the cards. It will probably take a couple weeks to clear it up, but they will get to it.
  • CaptButchCaptButch Posts: 10 Greenhorn
    Thank you so much, you've been a lot of help.
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