Bottom contour mapping via a dinghy

[geoffschultz]

I've been taking my 5'5" draft Freedom 40/40 in & out of the Rio Dulce in Guatemala since 2001 and have never had a problem. There's a bar at the entrance that's probably 1/4 mile wide and we always cross at the astronomical highest tides of the month. Last year we bumped very hard multiple times when going out and we had to get pulled across using 2 dinghies with 15 HP motors to make it in. We have a 6' wide wing keel, so heeling the boat doesn't help.


I've been using the same/current waypoints for years, so I suspect that the channel has moved or silted in. My goal is to take a dinghy out with some kind of sounding device to map the bottom contour before trying to take BlueJacket out through it.



Does anyone have suggestions for a reasonably priced solution to this? In the past I've just taken a hand held depth sounder and a handheld GPS and mapped things that way, but I was looking for something more automated.

[Tingum]

Put an inexpensive Hummingbird, transom mounted transducer on your dink. I always had one on mine as I have a habit of going where no man has gone before. Really helpful in cloudy water.

[Dockhead]

Originally Posted by Tingum

Put an inexpensive Hummingbird, transom mounted transducer on your dink. I always had one on mine as I have a habit of going where no man has gone before. Really helpful in cloudy water.

I am also interested in this. Will such a Humminbird record the depths with the GPS coordinates, so that we can display them on a computer or a plotter?


Have you done this?

[night0wl]

The bigger question is what do you do once you gather the data. I am so frustrated with Navionics/Garmin/Active Captain which has collected community depth data and then is now making them harder to use for those that don't pay for their charts.

Please consider a mechanism of collecting this chart/depth data and uploading to openseamap. Perhaps we can break the yoke the commercial co's have on OUR community reported data. https://depth.openseamap.org/

[GordMay]

Every year, over 16 million recreational boats traverse the nation’s coastal waters, compared to NOAA’s fleet of five hydrographic vessels. A high percentage of these boaters, especially among the larger vessels,use GPS and echo sounder systems, and in essence collect new, high quality depth data every time they transit from one place to another. TerraNautical has assembled and tested a device that captures and records
these data and has developed and tested a way to process the data to NOAA specifications utilizing a NOAA-style Quality Assurance review.
➥ https://www.terranautical.com/paper/tndhydro.pdf

Recreational boaters are already “collecting” data. However, just as quickly as their sounding data flashes onto their depth sounder it is, regrettably, lost forever. However, this does not need to be the case. With the advent of small high capacity microelectronic storage devices (CompactFlash), mobile telecommunications, and precise positioning technology such as WAAS GPS, most of these vessels could be recording the sounding data needed to improve nautical charts.
➥ https://www.terranautical.com/paper/...tm#_Toc2911181

Unfortunately, I don’t see any information on the actual “devices” they propose using.

[Jammer]

I use a Vexilar SP300 module connected via WiFi to an Android smartphone running Navionics. The SP300 is inexpensive ($150) and self contained, powered by its own gel-cell battery. Attaches to the survey boat with suction cups. Battery life between charges is longer than I've ever tried to run it, at least 20 hours.


There are other depth finders available that will provide the necessary data feed, but the Vexilar is the least expensive and most portable that I have found.



Any smartphone or tablet will work. I use a Galaxy S8, which is water resistant (IP67), and provides about 4 hours of useful battery life for surveying.



Navionics will collect the data and construct a contour map as you move around. You would then use the same smartphone while navigating the channel with the mother ship, as there is no straightforward way to transfer the data to a chartplotter.


The Navionics software is free to install but there is an annual chart subscription fee charged on a regional basis. It is not expensive.



The navionics application will also upload the data to Navionics' servers once an internet connection is available, and Navionics will then review the data and incorporate it into future chart updates, usually after a few weeks.


I do believe that openseamap is worthy of our support but am not sure that it solves this particular problem.

[Jammer]

Here is an example showing the confluence of the Mississippi with a local stream that forms a little inlet. The just-collected data is shown in red. It is possible to adjust the transparency and color to make an effective chart for your situation. In this example, you can see that the inlet has considerable shoaling.

[Jammer]

I had zigzagged around the inlet to try to get as much data as possible. A limitation of this approach is that the software-generated contours can make it look like there's data for areas that are not well sounded.


This survey was via canoe from an access upstream as planning for using the inlet to anchor in the future. It's a pretty little area.


There are some implausibly deep areas that are due to limitations of the sounder. If the depth is less than about 12", it will report over 30'.

[belizesailor]

Originally Posted by Jammer

I use a Vexilar SP300 module connected via WiFi to an Android smartphone running Navionics. The SP300 is inexpensive ($150) and self contained, powered by its own gel-cell battery. Attaches to the survey boat with suction cups. Battery life between charges is longer than I've ever tried to run it, at least 20 hours.


There are other depth finders available that will provide the necessary data feed, but the Vexilar is the least expensive and most portable that I have found.



Any smartphone or tablet will work. I use a Galaxy S8, which is water resistant (IP67), and provides about 4 hours of useful battery life for surveying.



Navionics will collect the data and construct a contour map as you move around. You would then use the same smartphone while navigating the channel with the mother ship, as there is no straightforward way to transfer the data to a chartplotter.


The Navionics software is free to install but there is an annual chart subscription fee charged on a regional basis. It is not expensive.



The navionics application will also upload the data to Navionics' servers once an internet connection is available, and Navionics will then review the data and incorporate it into future chart updates, usually after a few weeks.


I do believe that openseamap is worthy of our support but am not sure that it solves this particular problem.

Ive got a similar Vexilar unit permanenlty installed, but its also intended to be portable so you could put in dink to do exploration.

Integration with Navionics is easy and it saves the data of the track including GPS locations and displays on charts.

To my knowledge Vexilar's phone app is only a fish finder like display which does not store any history.

[mvmojo]

Years ago I and some others had an idea to out fit a remote controlled battery operated boat with a depth sounder. If unsure about a channel, send it out ahead of the big boat. At that time, the bugaboo was getting data back to the big boat. Now, with Wi-Fi, it should be fairly simple. Never did anything with it, but I'm sure there's some smart folks on this forum who could make it happen.

[RobinScurr]

I have a Vexilar SP200 SonarPhone T-Box on my dinghy, but I have an electric start motor, so have a battery. It's meant to be a fish finder, but also can be used to map bottom contours. You use Navionics to record the data via Wi-Fi. Works well....

[Old_Geezer]

Most of the major names have a contour mapping "fish finder" these days.

Saturday morning fishing shows are great for this info. Even my electric motor has a built in GPS.

https://www.westmarine.com/WestAdvis...n-Contour-Maps

https://www.lowrance.com/lowrance/type/mapping/

https://www.youtube.com/watch?v=stDdSkFepf4

[Scaramanga F25]

For this purpose, I use my handheld depth sounder.

Walmart $ 67. oo Price doubles + in marine stores.
Vexilar if I remember.

[Lepke]

I like to anchor in remote places in Alaska and Canada. Some places haven't had new surveys in 100 years. And some places had the bottom raise after the 1964 earthquake. I use a spare Furuno depth sounder in a small boat to sound out entrances and prospective anchorages before I risk the big, wood boat. The sounder along with a gps plugin and my laptop adds the new depth after I've corrected for the tide state. Enough passes and I've found all the rocks and shallow spots. Sometimes I can find a natural range and in a few places I've made rock pile ranges so I can visually stay in safe water and go back year after year.
After that, it's quiet and I have nobody bothering me.

[Dave_S]

Navionics can update your maps as you run around in your dingy if you are in WiFi range or buy a sounder that will take your Navionics chip and update it directly. You can chose to share these maps with Navionics or not.

I assume Navionics will want to see repeated information from multiple sources to use the information.

In areas frequented by boats I would always share but I think in uncharted areas I would only share if there was a danger.

http://www.navionics.com/usa/charts/...onarchart-live