Got my hands on one of these sonars that wifi into your iPad and update the Navionics charts as you cruise along. Good gear. Here is a screen shot where we went into an uncharted reef and then I set the sonar up in the dinghy to get us safely back out.
Once I had verified where the reef was (not) I was able to take some way points off the iPad and put them on the boat chart plotter to make a safe track back out
Here is a bay I ran the dinghy around in the dinghy to get some more detail. The depth readings are all linked to the local tide station so it records the depth readings correctly for the chart no matter what stage the tide is at.
These depth readings are then uploaded to navionics next time I log on to check for chart updates. And then a couple of weeks later everyone gets my chart readings when they update.
Try this link. I was lucky enough to get mine free from Navionics at a boat show. They are keen (Understandably) to have more people out there using these things so they can get the updates for their charts. Your more appealing to Navionics if you go to out of the way places.
www.vexilar.com/navionics
This technology is a game changer. Imagine if every boat had one. We'd have detailed accurate charts in no time.
Good on navionics for recognising the power of crowdsourcing information.
I have been looking at these for a while and wish I had one when I was in the Kimberly.
Your post has convinced me and I have just ordered one from Marine deals .
Will make it so much easier for next years Kimberly cruise.
Thanks for sharing
Hey Crusoe Ive been looking at this product for ages now. I've verified where the reef is on one too many occasions. The Navionics charts for Fiji are bloody awful though to be fair it does say quite clearly that a lot of the survey was derived from aerial photos.
Anyway having rearranged the coral at night a month or so back I am on the point of purchasing one. I'm particularly taken with the T-pod transducer because I reckon that I will be able to integrate it into an old kite board. I want to do this because I should be able to cover a heap more ground, well water, whilst having a good time using no fuel and basically going where we can see how deep it is.. We often do long down winders, up to 18 ks.
Are you using one of these or are you using the boat mount or portable?
Also Ive not been able to find very much in the way of info on the ease of uploading the info onto Navionics. Any advice on that?
Hello Japie, I was using the boat mounted version but never made it a permanent fixture. I had a pole at the back of the boat I could lower into the water when I wanted to use it on my yacht, but I could take it off and clip it on the back of the dinghy when I wanted to just motor around a bit. Using the dinghy also meant I could go in a lot shallower water without fear of the keel verifying the actual depth for me 
When I was in the dinghy, I would have a backpack with a small battery in it to power the sonar. Doesn't take much. I think the sealed battery was about 12v 6ah. Then I would sit the iPad beside me and watch the chart take shape as I motored around. I had some issues in the end with how fast I was going but I thing the sonar unit may have developed a fault. If I went any faster than about 4knts it didn't read the depth properly. This was not a problem when I first started using it so it may have just been a dud unit. It still works all long as I go slow. The brochure claims it can be used for high speed operation.
When you create a chart you can delete bits you don't want by holding your finger on the screen of the newly drawn chart and a menu pops up. Then you use your finger as if it was a rubber and where you swipe the screen it removes the chart. You then hit a menu button to confirm you want to delete what you just swiped.
As far as downloading charts, this is done automatically when you open the navionics app on your iPad and you have a wifi connection prior to opening the app. There are some menu options you have to select to allow this to happen but once you have selected these options, the upload is automatic.
As far as Navionics updating their charts for Fiji with your new information, you would have to check with them. I did some uploads from Vanuatu and New Caledonia but they never appeared on the charts. I got onto Navionics and they had some excuse like it was going to happen by the end of last year or early this year when they release "Sonar Maps" for the areas. I believe that if I had of done uploads for Australia, they would have only taken a couple of weeks to appear on their charts.
The best way to ask navionics about chart updates, is to send them a message using the Navionics app. Just go to the help menu and send them a message. If you do it this way, Navionics also get information about the device (iPad of android) you are using.
When you first start doing the uploads, you will get a link from Navionics to a web site that shows you if Navionics were successfully able to use your sonar uploads.
Even if Navionics do not update there Fiji charts straight away, the information you recorded is always on your iPad chart. But it would have been great (for me at least) if I could have had this information on my Raymarine chart plotter sooner than later.
Never been to Fiji but everyone say there's lot of uncharted reef in the area. Good luck.
