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Old 07-09-2017, 15:21   #1
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Problems with Navionics Sonar Charts.

My friends Neil and Ley on Crystal Bules have recently discovered some serious errors in the Navionics sonar charts--the hard way.

Crystal Blues: Navionics Sonar Charts & The Missing Reef
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Old 07-09-2017, 15:25   #2
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Re: Problems with Navionics Sonar Charts.

This is the event to which I alluded in another thread. Neil's post outlines the problem quite well, and should be required reading for any Navionics user!

Good thing that Crystal Blues is such a tank!

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Old 07-09-2017, 15:30   #3
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Re: Problems with Navionics Sonar Charts.

Yes, Don,

We've been in touch with them, too. You know, I think people should hold Navionics accountable. We have more than one boat lost, as shown in the Tanda Malaita thread, plus if how Navionics is relying on updating their charts is by groundings, somehow, that seems to me, just not right! If hard groundings, it costs the boat owners something for repairs. I do not think their "not for navigation" would hold up in court when compared to their advertising.

Navionics have been lucky so far, that no one has wanted to hold them accountable. The gaps are really scary.

Ann
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Old 07-09-2017, 15:51   #4
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Re: Problems with Navionics Sonar Charts.

I think Navionics' response to Neil was entirely reasonable. Not confidence inspiring, but reasonable. Reasonable from the point of view of what they can actually deliver. And it points to the sonar charts being entirely unreliable.

The charts are likely produced with some algorithm that weaves together several data sets into their final product. Clearly that algorithm is not foolproof, and given the millions of square miles of navigable water that they cover there is no human way of checking the accuracy of the output other than a QA process that selects specific areas at random where they are checked. So maybe 1%, if even that, of output gets checked by human eyes.

Personally, it points to the sonar charts as being unreliable...because it's clearly an inaccuracy that was introduced by the algorithm. No doubt those charts are riddled with them.

Short of a class action lawsuit I can't see them behaving any differently, unfortunately.
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Old 07-09-2017, 19:12   #5
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Re: Problems with Navionics Sonar Charts.

My perspective on this is colored I guess by when and where we have sailed. I do not 'trust' or expect 100% accuracy from ANY chart - even 'official' paper ones. I have always navigated expecting/knowing that there may be errors on the chart.

We very early in our cruising went into the pacific, (in the sextant days) when most of the charts were still several miles out and the french had not yet done their recent surveys. So we 'learned' in a place/time where the main features were in the wrong places and a lot of details were missing and wrong. And later we have cruised in quite a few places where the charts continue to be in error and missing significant details (like Chile).

So, fundamentally, I practice (and think others should) defensive driving, and alert watch keeping, expecting/knowing there may be chart errors. There are many many ways to be 'defensive'. Just for example an important one is to know the local signs for uncharted rocks and reefs - In chile you saw kelp on the water surface (unless there is a fresh water inflow nearby), while in Maine you saw an odd pattern/discontinuity in the lobster pots.

A second comment is that pretty much all the vector charts have 'quality' issues. Vestas for instance was using c-maps, i-sailor has reefs disappearing on zoom in, and Navionics has the problems described. The rasters do tend to have better quality, but still they have errors and cannot be 'trusted', and they are less 'user/process friendly' in several regards.

I'm personally not sure that singling out Navionics is really an accurate representation of the problem/situation (where all the vector providers have issues), and I'v had better success at getting change with honey than with vinegar.

That all said, the commercial chart providers can do better than they are. The technology and processes are available for them to produce much higher quality products than they are. And I do think it is useful for the community to point that out to them, that we want and expect they raise their game.
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Old 08-09-2017, 11:06   #6
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Re: Problems with Navionics Sonar Charts.

I disagree with Evans in this case. When I was sailing in places like the Fiji, the Red Sea or Indonesia, I didn't expect accurate charting. The problem with Navionics is that they have serious errors in their sonar charts in Maine where the underlying data is accurate. The fact that Neil was easily able to find additional discrepancies between the sonar and raster charts tells me that the cause is probably a faulty computer algorithm, rather than isolated human errors.

The Navionics response to the problem is disconcerting-- they say if you find the errors (the hard way) and tell us, we will fix them. Navionics needs to discover their faulty algorithm, fix it, and reissue the charts --without charging their customers for an 'upgrade'. If they think that labeling their products 'Not for Navigational Use' is going to protect them, they are in for a rude awakening.
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Old 08-09-2017, 12:22   #7
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Re: Problems with Navionics Sonar Charts.

Navionics says "Not for Navigational Use?"

Do the other electronic chart providers say the same? (Serious question?)

If so, which ones do?
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Old 08-09-2017, 13:55   #8
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Re: Problems with Navionics Sonar Charts.

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Navionics says "Not for Navigational Use?"

Do the other electronic chart providers say the same? (Serious question?)

If so, which ones do?
They pretty much all have the warning that these electronic charts are not to be relied upon implicitly. This is for several reasons. First, the lawyers for the companies want the companies to protect themselves. It is no different than the hairdryer company issuing a warning that the hairdryer is not to be used in the bathtub.

Second, if it is on the Internet it MUST be true. Too many idiots think that electronic charts and navigation is dead on balls accurate. They forget that charts, whether electronic of paper are guides and are not infallible. This results in the companies trying to make people aware that they need to take the results with a grain of salt.

Third, even if the charts and navigation are 100% accurate, electronic devices tend to degrade situational awareness. There was a guy in one of my yacht clubs who used buoys as way points. In this case the navigation was, sadly for him, 100% accurate. His boat sailed into the buoy and sank.

In twenty or forty years perhaps artificial intelligence will be so good that you can flip a switch and the navigation system will take you from A to B without the need for you to pay attention. When this happens however you will no longer be a sailor, you will instead be a passenger who happens to own or charter a boat.

I sell this stuff. They all warn one to not use this as a primary means of navigation and they are correct for doing so. You should navigate and then use this to assist your navigation.
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Old 08-09-2017, 15:33   #9
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Re: Problems with Navionics Sonar Charts.

Quote:
Originally Posted by Steady Hand View Post
Navionics says "Not for Navigational Use?"

Do the other electronic chart providers say the same? (Serious question?)

If so, which ones do?
Raster charts distributed by VisitmyHarbour are officially marked "For Navigation".

No chart is 100% perfect, but I personally take notice and have respect when a publisher is willing to sign up to this. And I always wince when I read the weasel words on my Navionics charts.
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Old 08-09-2017, 16:35   #10
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Re: Problems with Navionics Sonar Charts.

A paper chart that is not fit for navigation (due to age or inaccuracy in data) makes an attractive wall hanging. What use is there for an electronic chart that is unfit for navigation?

Jim
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Old 08-09-2017, 17:23   #11
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Re: Problems with Navionics Sonar Charts.

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A paper chart that is not fit for navigation (due to age or inaccuracy in data) makes an attractive wall hanging. What use is there for an electronic chart that is unfit for navigation?

Jim
Amen.

Especially one which you just spent 100 quid updating
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Old 08-09-2017, 17:39   #12
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Re: Problems with Navionics Sonar Charts.

I just returned from cruising right through there, so I was curious which reef was so poorly represented by Navionics. Here's a screen grab from OCPN, with an arrow to the reef in question.

While Navionics seem to be insanely negligent in how they compile their Sonar Charts, it must be said that Potts Harbor is one of the most well-buoyed you'll ever encounter, and a red nun does mark this reef.

It's a lesson we all have learned over and over.... Don't get lost looking into your screens instead of out at reality.
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Old 08-09-2017, 17:53   #13
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Re: Problems with Navionics Sonar Charts.

Very salutory message. Personally I have not been induced to use the sonar chart display, I prefer the chart presentation. This has been particularly true since Navionics started their user/community input of sonar data. That scared me. How could Navionics validate the data? Sure some new dangers may be identified but also mis-identified.

I have looked at 'user/community' data marks which have been published on the ipad/android chart systems for places I know and I have frequently found them to be inaccurate when I go there myself. Too much room for error to rely on.

As for the sonar community info, it is axiomatic that there will be very little accurate information from users about the MOST shallow spots - 99.9% of boaters don't go there because they are too shallow - so even if you provide valid data to Navionics close by to the shallow reef it does not include the most shallow points.

Maybe the problem is as simple as Navionics getting so much data from user input which indicates sufficient depth (say 5m near the 1m reef) that their algorithm to blend the information just adopts the more frequent deeper readings and earlier shallow data from hydrographic surveys is over-ridden/swamped.

Whatever the root cause, Navionics are certainly tainting their product and brand and need to resolve it.

For me, I'll stay away from the sonar displays and also continue use my C-Map android app as a cross-check to the Navionics on android and my Raymarine E120W.
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Old 08-09-2017, 22:11   #14
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Re: Problems with Navionics Sonar Charts.

Quote:
Originally Posted by Cormorant View Post
I just returned from cruising right through there, so I was curious which reef was so poorly represented by Navionics. Here's a screen grab from OCPN, with an arrow to the reef in question.

While Navionics seem to be insanely negligent in how they compile their Sonar Charts, it must be said that Potts Harbor is one of the most well-buoyed you'll ever encounter, and a red nun does mark this reef.

It's a lesson we all have learned over and over.... Don't get lost looking into your screens instead of out at reality.
The reef is adequately marked, as to the attached map

Which additional caution is needed not to go there!?
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Old 08-09-2017, 22:48   #15
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Re: Problems with Navionics Sonar Charts.

Quote:
Originally Posted by Cormorant View Post
I just returned from cruising right through there, so I was curious which reef was so poorly represented by Navionics. Here's a screen grab from OCPN, with an arrow to the reef in question.

While Navionics seem to be insanely negligent in how they compile their Sonar Charts, it must be said that Potts Harbor is one of the most well-buoyed you'll ever encounter, and a red nun does mark this reef.

It's a lesson we all have learned over and over.... Don't get lost looking into your screens instead of out at reality.
indeed that's a better and adequate representation.

I got it wrong, then l read the article by the unfortunate sailors.

In the Med, navionics platinum+ soundings are to my knowledge pretty accurate. But I use them for anchoring, rather than for navigating in close quarters
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