Surveying Anchorages in Uncharted Waters from the Dinghy

[Pete7]

Dockhead, you need another gadget on board, one of these:

The Best Underwater Drones - 2018 | Top 10 Drone

[Uplander]

Is it possible to insert a hand made chart into OpenCPN? If so how?

[myocean]

Use google satellite data - in most regions you can very well identify rocks, shallow areas etc. There is software around which allows to have the relevant data offline on your pc and very accurately display your exactg GPS position on the screen:
"SASPlanet" very comfortable takes the data you need from google, stores it locally and provides it when you have arrived at your destination.

[hellosailor]

Dockhead-
I don't know what the practice in the Baltic is, but if you were in US waters, the LNTM used to say rightup front that the US hydrographic office (whatever they've been Borged into these days) actually encouraged mariners to send that kind of data in, so that it could be added to the official hydrography. That doesn't mean they'll take it on faith right away, but the information is accumulated and in theory eventually used.

[flyingfin]

Your hand will get tired quickly. Try mounting a transducer on the end of a piece of 1" PVC pipe and strap it to the transom of the dingy

[Chuck Hawley]

I surveyed a lake that was 3 mi x 1 mi in the Sierra using a Vexilar sonar, connected to an iPad mini via wifi, and then by sending the data logs to Navionics. Very fun, and very accurate. Some frustrations when you lose the signal and you record very shallow readings when in fact the depths were too great for the little Vexilar transmitter. I did this using a 12' inflatable and a few days of time. If you look at Fallen Leaf Lake, south of Lake Tahoe, this is my data.

It can be done, but my creation of charts was done by sending them to Navionics via the web, and then receiving back updated charts during the refresh process.

Chuck Hawley

[Sojurnr]

Originally Posted by mvmojo

I had a project a number of years ago to outfit a remote controlled small electric boat with a depth sounder, gps module and a wifi transmitter. The idea was to drive the little boat around a potential anchorage or inlet and automatically chart the depths. Unfortunately, it never got out of the planning stages, but I still think it's a cool idea! Looks like the technology exists in a pre-packaged form with Sea-Bee's little chartplotter. Gotta think about putting one of those on an R/C boat....

Just reverse engineer a Roomba to be waterproof and fit on a boat, add the GPS, WiFi emitter and a chart plotter. In business!

[sea-bee]

Originally Posted by Dockhead

OK, that's cool. So you are concretely doing what I asked about, and you do it using the Navionics Sonarcharts technology. Great; I'll look into that. Meanwhile it would be great if you could provide concrete details of how it works and what the procedure is.

System is quite simple. The Dragonfly Pro displays are little fishfinders with chartplotter supporting a number of different chart cards. Luckily, I paid extra for a Navionics card. What is particularly smart and different from other devices with wifi access is that the wifi does not simply mirror the display, but rather transmits data. This means that you can buy the model with the piddly little 4" display real cheap (around the same price as the Sonarphone sounder that I had been considering) and still get a decent image on a remote device like a tablet.

Installation in the dinghy required 12v power. I bought a little battery https://evparts.com.au/12v-lifepo4-b...evh12v7ah.html As I have LiFePO4 house battery on the yacht, I chose the same chemistry for the dinghy. I charge the dinghy battery by plugging it into the house power and equalising. I can either remove the battery from the dinghy and plug it in at the nav station, or when the dinghy is up on davits, it can be plugged in there. Having this little battery means that I can now add LED nav lights to the dinghy too. The setup is new, and I have only used it for a couple of hours, but there was no decrease in battery voltage (typical for Li-ion) so I'm not sure of the range available. Specs of the Dragonfly say 0.8amps so I should get 10 hours.

The sounder came with a proprietry transducer that is mounted onto the dinghy. The displayhead is mounted on a piece of plywood that I spring clamp to the thwart in the dinghy, allowing quick removal. Transducer and power come from one plug on a y-cable that is fitted in the dinghy. The dinghy is currently at home getting sanded down to undercoat and repaired, so I can't offer any photos for a few more days.

Operation is simple. Power on the Dragonfly. My tablet is a cheap Samsung Galaxy. Connect the tablet's wifi to the Dragonfly hotspot. Start Navionics. In the Navionics menus, connect to the Dragonfly. Once it sees the sounder, it starts updating the sonarchart with the new data. Drive around in the dinghy surveying the depth not only under the dinghy, but about 20m wide strip either side of the track. Settle on a route and take some waypoints.

My B&G chartplotter on the yacht has a C-Map card. I think if it was a Navionics card I could transfer the data onto the yacht's display, so the tablet is required to navigate using the newly surveyed data.

I have tried the C-Map card in the Dragonfly, but the Navionics on the tablet does not see the data coming across the wifi. So make sure to pay extra for the Navionics card in the Dragonfly Pro if you want to use it in this manner.

Chris

[JPA Cate]

This will make you laugh, most likely, but we did this, the old fashioned way: sounder was one of these: https://www.whitworths.com.au/hondex...-depth-sounder

Used a hand held Garmin, recorded possies where we took readings, transferred to paper chart, gasp! by hand. An afternoon's project.

Cheers,

Ann

[Dockhead]

Originally Posted by JPA Cate

This will make you laugh, most likely, but we did this, the old fashioned way: sounder was one of these: https://www.whitworths.com.au/hondex...-depth-sounder

Used a hand held Garmin, recorded possies where we took readings, transferred to paper chart, gasp! by hand. An afternoon's project.

Cheers,

Ann

Doesn't make anyone laugh, of course - that's the classical approach and what we might well end up doing anyway. But it's slow, inefficient, and imprecise, so we're thinking about more efficient ways to do it. We will be time limited up there and I don't want to spend whole afternoons surveying anchorages, when I could be scrambling around on glaciers and running away from polar bears.

[RaymondR]

I have done dingy surveys to enter anchorages using both buoys made from light weights, light cord and plastic soft drink bottles which I retrieved on the way back out and GPS information.

Doing them with a handheld GPS(Magellan)

I created start and termination way points then a route,

then switched to the DMG and XTE display and

on finding the deep water with a sounding line(3/8" poly dingy anchor line with flags made from the bristles from a broom with a fold up anchor)

noted the DMG and XTE until the termination waypoint was reached.

I did not try to make a contour chart but made a plot from which I extracted the headings from point to point.

To run the plot I used the DMG from the GPS whilst running the compass courses with an eye on the sounder.

You can get pens and survey books with water proof paper from Surveying supply stores. Very handy in the marine environment.

[Jammer]

Dockhead, here's a related thread I started a while ago:

https://www.cruisersforum.com/forums...ht-194601.html

I have been using the Vexilar Sonarphone setup in my canoe for a couple of years now. They are available in a two form factors. One is the "oversized fishing bobber" described upthread, which is mainly intended for surveying areas inaccessible by boat. The other is a fairly standard suction-cup mount transducer, with a cable that goes over the transom/gunwale to a brick inside the boat that has electronics and a small gel cell battery. I have the latter.

Either way, the devices connect to a smartphone using Wi-Fi. For use in my canoe, I have a wheelbarrow inner tube around the brick to allow recovery in the event of capsize. I presently have a water resistant phone, but previously used a cheap vinyl case around my older phone. I run the Navionics software on my Android phone. It accumulates soundings and builds a chart as it goes. Navionics publishes the data.

All the soundings on the Cannon River and Lyman Lakes that are now available from Navionics were taken by me in this way:

https://webapp.navionics.com/?lang=e...y=i%7BinGpirwP

If you follow the Cannon down to Lake Byllesby, you'll see where the soundings join the exisiting charting along the route I take. This area benefits from data collected by power boats, which are more frequent users of Navionics.

The advantage of this approach is that you don't have to do anything but set up the sonar and run the software. It does the rest, and eventually, you get better charts.

There are some drawbacks.

1. It takes an internet connection, and some time for Navionics to vet and republish the data -- typically about a week. So it's fine for exploring areas you'll come back to, but for situations where you're exploring an area for immediate navigation, you have to use the same phone on the yacht, or figure out how to store the data and transfer it. (It is also possible to move the yacht's chartplotter to the dink.)
2. Navionics smoothes the data and edits it at their discretion using automated tools. The main problem with this is that it is impossible to tell where the data is based on soundings, and where it is interpolated.
3. While it is possible to mark specific locations this way, the process is somewhat cumbersome particularly if trying to record soundings rather than a point of interest (rock, wreck, etc)
4. You have to pay for a subscription.

[Dave_S]

Is this what your after ?

https://youtu.be/aoIONFjYlQs

https://www.navionics.com/aus/charts...onarchart-live

[billdre]

Dockhead, if the primary goal is not spend a lot of time charting an anchorage why use a dingy to do the exploring? I bought a hand held depth finder and plan to sit on the bow of my boat, slowly checking depth as we go. I've only tried it out in our harbor, New Bedford, MA. It works well to check the edges of shallow water. No charting, just get in, check the area for scope and anchor. I don't have the multiple electronic gadgets nor the desire to truly explore uncharted worlds.

[wholybee]

OpenCPN will record NMEA data,and I'm sure lots of other software will also. It might be a bit complex to set up in a dingy, but a depth sounder and GPS connected to a laptop and record the NMEA stream. GPS position and depth at intervals. Then, parse that (would need to write a custom program to do that) to create waypoints with depth data that could be loaded into a chart plotter.