Navionics in S Pacific - beware!

[Albro359]

We have always had C-Map charts and found them to be very good representations of the reality in our area - the South Pacific.
I recently bought a b&G plotter primarily for the Forward Scan function.
The package deal included a chart card so i got Navionics, South Pacific Islands.
When I used it in Fiji I was shocked at the inconsistency of the charts. In some places Navionics was accurate and well detailed. In others, compared to C-Map it was inaccurate and misrepresented channels and reefs to such an extent that I consider it to be dangerous. You certainly would NOT want to navigate the Yasawa Islands with only Navionics, yet i came a cross a number of cruisers who only had Navionics on an iPad, no paper charts, no other alternatives.
I attach a file of screenshots that demonstrate exactly what i found.
I send this message as a warning to those who depend on only one source of navigation information.

[boom23]

I do not know of any accurate Fiji charts. When we were there, 3 years ago, we would only navigate when the sun was overhead or behind us, so that we could see the uncharted reefs.

In SavuSavu, Curly does a seminar and provides more accurate waypoints to navigate tricky/popular areas. Here is his website:

CURLY, in Savusavu, Fiji

[Albro359]

The C-Map charts are an accurate representation of the Yasawas. They are based on the official F5 chart and Pickmeres folio 105 charts and as such they are about 0.25 of a mile out...so GPS positions need to be moved 0.25 of a mile E.
Admiralty charts of the rest of Fiji we have found to be accurate.
Of course we always navigate when the sun is up and we can see. I've been sailing around here for 10 years and I don't trust other people's waypoints

But that's not my point.
My point is that the Navionics charts for this area are a gross misrepresentation of the reality and are dangerous....you can see that looking at the pictures I attached.

[Paul L]

We found up-to-date CMAP charts to be very good in Fiji, from the Yasawas in the west to the Lau in the east. Not perfect, but very good

[estarzinger]

It would be interesting if you go to navionics webapp and see if the chart representation there was the same as what you see on your boat. We discovered a bit ago that in Polynesia they had a translation error from their base world map, which was correct and shown on the webapp, to the plotter and phone files which had errors. When it was pointed out to them they quite quickly corrected it.

If the webapp map is incorrect, then you would do a service to the community contacting them directly showing them what the errors in what their chart shows compared to official charts (they would not be very interested in what cmap shows). If you do that they will make corrections (have every time I have done it).

[Albro359]

I checked the webapp and it is exactly the same .... wrong...

what I don't understand is how it could be SO wrong, when there are official charts available that show the correct detail.

I have sent all the information to them, so we'll see what happens.

[philiosophy]

Unlike Say Tonga, as far as I know Fiji has not been surveyed and charted since in some parts back to WW 2 or even before.This year a day or two after checking in we were boarded by a joint Fiji Kiwi navy training operation. I asked the Seasoned Kiwi officer if they were going to survey and chart Fiji like they did a few years ago in Tonga. He said they were talking about it and it is possible.
There is how ever a very good solution that we now employ especially in Fiji. We have Open CPN with the Goggle Earth charts loaded in the system. This puts your boat Icon right in the Sattelight picture which can be blown up to very good detail. I have cruised Fiji from Savu Savu to Denerau and up into the Yasawas the last two years. I have only found it to be amiss one time.That was a Ship channel marker between Musket Cove and Denerau. Some how the Sattelite imagry missed it. Really takes the sweat out of cruising Fiji.
I can’t imagine not having this Free system aboard. I would be tempted to make it the primary Nav system at the Helm if I could figure out a robust daylight screen. As it is its far and away our most trusted navagation system aboard and the only one I know that will work with Google Earth charts. We have it on both laptops.
I know of a nice boat on the bottom of a reef in Fiji that I understand had only Navionics on a Ipad. I like Navionics just fine and have found it very accurate all over the South Pacific. Not anything like the Garmin Blue Chart system I had before which was not good from Marquesas and increasingly so as we traveled farther west.

[Albro359]

We use OpenCPN extensively as well.
We have MaxSea TZ on the laptop running C-Map, Navionics and raster charts with OpenCPN statellite photo charts on the same screen side by side. That way we can directly see the differences. We have a wireless router connected and use a tablet at the helm as a screen repeater for the laptop.
But again, this is not my point.
My point is that the Navionics charts are so bad and it has nothing to do with surveys. The charts are just plain wrong. They don't reflect the available information.

[Cpt Pat]

Are both your charts and your GPS using the WGS84 datum, or did someone in the middle of the night twiddle your GPS to something else?

https://en.wikipedia.org/wiki/Geodet...m_1984_(WGS_84)


It's happened before: https://www.yachtingworld.com/blogs/...own-reef-60753


There can be huge disagreements between datums (miles). And even with matching WGS84 datums, I always assume a minimum potential error of 1/2 mile between GPS positions and positions depicted on a chart (electronic or paper). You may know your lat and lon to within centimeters, but that's no assurance the rocks and reefs are accurately portrayed to their lats and lons. Relative positions between objects on a paper chart, sighted manually with a sighting compass, are usually quite accurate on a well-surveyed chart. But there may be large errors with regard to their absolute lat and lon on the chart or chart plotter. If the earth were only perfectly spherical, and if "local vertical" always pointed exactly straight down, then charts wouldn't be a compromise between relative positions and absolute (GPS) positions.

[philiosophy]

Hi Alan, how are the Navionics in New Cal and Australia. I see I am entirely misinformed and didn’t look at your provided screen shots. My apologies and now I am wondering if I should get my Old C-80 total world chips updated. It will be good to know if Navionics is playing Silly Bugger like Garmin was. We too are cruising in Vanautu and then Loyalties the 22nd of Sept. I would like very much to have more conversation on this topic in person over a beer if we happen to be in the same place at the same time. Wanting to get up to Luganville tho am concerned about the ash. kimphilley58@gmail.com

[Cloroxbottle]

Originally Posted by Albro359

We have always had C-Map charts and found them to be very good representations of the reality in our area - the South Pacific.
I recently bought a b&G plotter primarily for the Forward Scan function.
The package deal included a chart card so i got Navionics, South Pacific Islands.
When I used it in Fiji I was shocked at the inconsistency of the charts. In some places Navionics was accurate and well detailed. In others, compared to C-Map it was inaccurate and misrepresented channels and reefs to such an extent that I consider it to be dangerous. You certainly would NOT want to navigate the Yasawa Islands with only Navionics, yet i came a cross a number of cruisers who only had Navionics on an iPad, no paper charts, no other alternatives.
I attach a file of screenshots that demonstrate exactly what i found.
I send this message as a warning to those who depend on only one source of navigation information.

You aren't the first person to have made the observation that the further you get from coastal North America, the further Navionics gets from reality. Can't say one way or the other from personal experience.

[Perfect Ride]

Thanks Alan,

Nothing like a quality photo from Google, Bing or Apple to validate the accuracy of someones drawing and nothing like a set of eyes in good light to validate the details of a photograph taken from space. We will see you around Vanuatu, soon on our way north to the Banks ...