OCC Forums

Using iPad and Navionics as Chart Plotter


By mina - 15 Mar 2013

Many people are being woo 'ed by the cheap Navionics (and Garmin I believe) apps for iPhones and iPads. I have been experimenting with using an Ipad as my principal chart plotter and have concluded that the concept is a non-starter.

I have been cruising the east coast of South America over the last three years from top to bottom (and back). The C-Map coverage on my chart plotter for many of the places I have been to has been non-existent. The Navionics cartography was infinitely more comprehensive. So I decided to experiment with using an iPad in a waterproof housing as my principal chart plotter, using iNavX chart plotting software and downloading Navionics charts. I also have a Vesper XB8000 WiFi AIS transponder that streams AIS data as well as all the boat 's NMEA 0183 or 200 data to the chart. In theory this gives you almost everything a dedicated chart plotter provides, but for a fraction of the cost (and you have all the other functionality of the iPad to boot). However, I have found that it is unusable as a principal chart plotter because:

1.In bright sunlight, the chart can barely be seen
2.In hot climes, just at the point when you need it most, the screen blanks out with a message saying it is too hot, and cannot be rebooted for at least 10 minutes
3.When the screen gets wet from rain or spray, the touch screen doesn 't work - it has to be wiped dry every time you want to do anything like zoom in or out.
4.During the day, even when plugged in to a charger, the draw from the software and the brightest setting causes the battery to slowly drain.

Whilst the arrangement is great as a standby that you can use, for instance, at the helm when conning in or out of anchorages, it is sadly not fit for purpose as a principal chart plotter. So back to the drawing board and the cheque book!

Tim Barker, S/Y Mina2
By DariaBlackwell - 16 Mar 2013

Tim, thank you so much for this post. We have been discussing this issue at length, deliberating which way to go. What you have said makes great sense. At least you can use your iPad for reading books and email!
By David.Tyler - 16 Mar 2013

"Different ships, different long splice", I guess. My experience is very different, anyway. However, I see any type of chartplotter as not being the principal means of navigation until you get up to the full-on ECDIS big ship nav systems, with built in redundancy and backup. Until you get to that stage, paper chart and GPS is the principal means, and a chartplotter is a great means of adding another layer of information, even if it 's not 100% reliable. Even the big ships carry paper charts.

Anyway, back to the iPad. I 've just sailed up through the tropics, Tahiti to Hawai 'i. I kept the iPad running all the way, plugged into the 12v socket. I read some novels in iBooks, listened to some music. No problems with keeping it charged. I don 't need to keep it out in bright sunlight. If I need to see it from the helm, I put it on the companionway step. If there 's any moisture about, I put it in a Ziploc bag, and have found no problem with the touchscreen. The screen is much, much better for daylight viewing than my Macbook, and Ive given up on OpenCPN and the like for navigation.

No, the iPad is great for those times when you actually need a chartplotter for info in real time, such as entering a strange port at night, and weaving between hidden dangers when the visibility is poor and landmarks not abundant. Other than that, when you 're offshore, what need of a chartplotter? Only, as far as I can see, to avoid having to buy and carry a shipload of detailed inshore charts. For my trip through the Kenai Peninsula and Prince William Sound this summer, I 've got 1:200,000 paper charts, and will happily be using the iPad, and Transas iSailor and Garmin BlueChart, when the vis is poor, and when I 'm exploring the nooks and crannies.
By the Admiral - 21 Mar 2013

I thought I would add my experience with an iPad. We have a Ship Modul multiplexer that outputs NMEA data inc AIS over wifi. We are able to add waypoints and drive the pilot from the iNavX system. However, if the iPad is set to go to sleep then that function switches off!

We have a Raymarine plotter below and I was keen to be able to switch off the plotter whilst on longer passages and so the iPad is great for a quick check. We also use a waterproof bag that works well in wet conditions.

The other advantage of having a wifi tablet (iPad and Kindle Fire) on board is to be able to connect to the ship 's wireless router that can be connected to wifi (when in range) or satphone (when funds allow)

So, I like it very much and it suits our use perfectly.

By dcaukill - 16 Apr 2013

I would not dismiss the IPad so quickly.

We use it a lot, particularly where we can also get a phone signal because we cross reference the Navionics against a Google Earth.

I spent about $100 on a purpose built water/ shock proof cover - don 't recall the name - but it works and is pretty much bomb proof. If you don 't have a 3G signal you will need to spend time caching charts before you set off but I have found it in valuable because you can cross check your chart against. Google Earth using the same GPS fix.

Why is that important? Well, it allowed me to get out of the Fiji reefs leaving Musket Cove about A mile earlier than those using charts alone. It allowed me to navigate around Fiji where the Navionics simply gave up, and in Bland Bay, NZ it showed me the rock we were to ground on, some 70 metres from any navigational danger marked on the chart - sadly, after we had hit it!
By dcaukill - 9 Jul 2013

And the IPad proved a great back up when my chart plotter failed ( or more accurately, the SD Card corrupted) in Vanuatu last month.

iPad invaluable.
By igsims - 27 Jul 2013

We use IPad that does not have GPS but with XGPS150 unit connected by Bluetooth. Navionics basic app, UK chart package.. Used it instead of our laptop CMap system during Scottish OCC cruise recently. Accurate, fast, no prob with bright sun but we usually keep it below decks. Big bonus is it uses less power than laptop, good for ships batteries.

Doubt if it is robust enough for long voyaging but I 'm quite happy to use it for coastal cruising with paper chart available.

Ian Sims
By David.Tyler - 1 Aug 2013

I 'm in Prince William Sound, Alaska. I have the paper charts, but they 're difficult to read when I 'm exploring the minor channels and tiny coves where the US Coast Pilot says "not to be entered without local knowledge". The iPad is proving to be totally reliable, and I can zoom right in to see the detail that I can 't make out on the paper chart. However, one app is not enough. I have Garmin Bluechart and iSailor, and frequently have to compare one with the other, and choose the one which has the better detail. Though they 're both based on the NOAA charts, they do vary as to what they choose to include.
By EdKelly - 1 Aug 2013

We have loved the iPad and used it as a strong adjunct to our Raymarine E120 and our Mac MacENC computer when crossing the North Atlantic to good avail in 2011... We use it intermittently inside & out in good wx only. (The 1st non-3G iPads in USA did not have GPS chipset, but that was not a problem with us.) During our circumnavigation of Europe (at least the old Roman Empire part of it) we particularly have liked both the Navionics Charts and the iGrib program. We used it navigating the rivers Rhein, Main, and Danube but found no charts of value on the lower Danube (where they just show the river in a useless solid use blue color). But from the Black Sea, through the Bosporus, Sea of Marmara, Dardanelles and Aegean to the Med, all the way to Gibraltar... where we are now ... it has often been a Godsend. We also have relied on the App from the Cruising Assn with all its Captains Mate for finding good anchorages, which are available when offline! We also are very impressed with upgrades that continue in iNavX program and like the newest WeatherTrack app. You can see the latter in operation on YouTube. Finally, we are today downloading the App for iPad that Iridium and App for XGate that let you do email and wx downloads from our Iridium Sat Phone via WiFi accessory.
By simoncurrin - 1 Aug 2013

Ed I think iPad navigation has really come on in recent months. It 's worth taking a look too at the Garmin charts for iPad (BlueChart) which are also relatively inexpensive (when compared to Chart plotter versions) and integrate with Active Captain as well as GRIBS, weather radar etc.

It won 't be long before we are all wondering how we ever managed without an iPad on board!

By David.Tyler - 11 Sep 2013

Here 's a funny thing - as I was leaving Cordova, some weeks ago, the iPad failed to get a GPS fix. That was OK, I could still refer to the charts and use my trusty Furuno GPS for fixes. It stayed that way until I was in Pelican, when the iPad got an approximate fix from the cellphone system, and then failed to fix when I went out of range again. A few days later, in a remote bay with no cellphone system, the iPad GPS started to fix again. All the time, the Furuno had no difficulty in fixing, so the GPS system itself was operational. I can only put this down to the iPad needing to have an approximate idea of where it was before it could reload its almanac. But why did it fail to fix in the town of Cordova??? And why didn 't it get an immediate GPS fix when I was in Pelican???
By simoncurrin - 12 Sep 2013

Never had this problem with an iPad but I wondered if anyone has had any experience of GLONASS - the Russian sat nav system. I bought a new camera last week (just. £200 compact) but it boasts that it fixes position (for geotagging photos) by both GPS and GLONASS. So can all current gps receivers use both GPS or or just the newer ones? Presumably if the Pentagon throws the switch I 'll be able to still navigate by camera!!
By DariaBlackwell - 12 Sep 2013

We decided to head off for a sail earlier this week when we heard the Azores high was settling back in over Ireland! As we were leaving our inlet, the GPS (no differential) started dropping in and out of the chartplotter. Alex tried to jiggle wires thinking it was a bad connection. We were waiting for our back up GPS to launch when it suddenly came back into action with differential, about a half hour into it. When we looked at satellite acquisition, there were five satellites out of commission. We had heard that the aging satellite system was going to cause problems with GPS this year, and this is the third time we 've had a problem. I 'll post photos of the anomalies we experienced in Scotland in July as well.

But I LOVE your navigation by camera. Point and shoot naavigation. I just picked up a new Samsung android and the Navionics charts are pretty cool as a backup on there, as long as the gps works.

I still love paper charts.
By DariaBlackwell - 24 May 2015

I just read this blog about lightning strikes and wondered if any of you protect your electronics if there are electrical storms around. Any experience with lightning strikes and electronics?

By DariaBlackwell - 24 May 2015

[quote="simoncurrin" post=1109]Never had this problem with an iPad but I wondered if anyone has had any experience of GLONASS - the Russian sat nav system. I bought a new camera last week (just. £200 compact) but it boasts that it fixes position (for geotagging photos) by both GPS and GLONASS. So can all current gps receivers use both GPS or or just the newer ones? Presumably if the Pentagon throws the switch I 'll be able to still navigate by camera!![/quote]

UPDATE: As of 2015 most smartphones now include GLONASS navigation.
By DariaBlackwell - 24 Sep 2017

There is a growing body of evidence that Navionics Sonar Charts, and indeed their regular electronic charts, have major inaccuracies. Two serious accidents have recently been reported. Please read the report from Crystal Blues if you use Navionics charts. They collided with a reef in Maine that was missing on the charts.


Similarly, a family of four sailing Tanda Malaika, a catamaran, collided with a reef in the Pacific. Fortunately, all were rescued unharmed. The yacht was not insured and an expensive salvage operation was required. They had been using Navionics charts.

"[color=rgb(102, 102, 102)][font=Raleway, Helvetica, Arial, sans-serif]When they asked us what happened and we told them that our chart did not show reef, they asked us if we had been using Navionic charts, and I said yes. He then shook his head and said that at least five boats end up on those reefs a year who were using Navionic charts. They walked me over to a large map on the wall and told me to point exactly to where Tanda Malaika was, and I did to the best of my knowledge. They then pointed to two places, our spot being one of them, that all the wrecks seem to happen, then gave us the name of a man who we could call for salvage help. The word ‘salvage’ seemed so cold and final. It sounded to me like death."[/font][/color]


Have you had experience with inaccuracies on Navionics charts?
By simoncurrin - 25 Sep 2017

Yes we noted plenty of inaccuracies in Navionics this summer. This included reefs that weren't marked, shorelines half a mile adrift from their charted position and, of course, plenty of islands that didn't exist. The trouble is these errors were also present in CMAP and Garmin's Blue Chart all of which we carry. I think the problem in remote waters is that the electronics are all based on paper charts drawn from ancient surveys. Not sure where that leaves us other than to recommend greater use of forward looking sonar, KAP charts from Google Earth and, perhaps, drone surveillance. Interesting one of the first boats to transit the NW passage this season (East about) attributed their success to deploying a drone to reconnoiter the ice conditions.
edited by simoncurrin on 9/25/2017
By simoncurrin - 25 Sep 2017

[color=rgb(144, 148, 156)][font=inherit][font=inherit]Daria Blackwell[/font] shared a link.[/font][/color]
[font=inherit][/font][font=inherit][font=inherit]24 September at 11:46[/font][/font]
OCC Members Neil & Ley Langford have written an important blog post about their grounding experience while using Navionics Sonar Charts in Maine. I have added it and other reports to an OCC Forum post about Navionics charts on iPad. Please contribute your experience there.
[font=inherit][font=inherit][font=inherit]Daria Blackwell[/font] [font=inherit][font=inherit][font=inherit][font=inherit][font=inherit]The original report from Crystal Blues. [/font]http://svcrystalblues.blogspot.ie/.../urgent-boat-repair[/font][/font][/font][/font][/font][/font][/font][/font][font=inherit][font=inherit]

[font=inherit][font=inherit]Neil Langford[/font] [font=inherit][font=inherit][font=inherit][font=inherit][font=inherit]Daria, the actual original report is here : [/font]http://svcrystalblues.blogspot.com/.../navionics-sonar...[/font][/font][/font][/font][/font]
[font=inherit][font=inherit][font=inherit][font=inherit][font=inherit][font=Georgia, serif]Navionics Sonar Charts & The Missing Reef[/font]
[font=inherit]Travel, sailing and cruising aboard sailboats,…[/font]
[/font][/font][font=inherit][font=inherit][font=inherit]Anne Lloyd[/font] [font=inherit][font=inherit][font=inherit][font=inherit][font=inherit][font=inherit]We also went on a reef in Fiji that was not marked on either Navionics or open Cpn CM93[/font]
[font=inherit]We knew however that in Fiji there are massive inaccuracies in all charts in relation to reefs and indeed whole islands in the Lau[/font]
[font=inherit]I do not however particularly Bla[/font][/font]...See more[/font][/font][/font][/font][/font][/font][font=inherit][font=inherit]

[font=inherit][font=inherit]Sherry Day[/font] [font=inherit][font=inherit][font=inherit][font=inherit][font=inherit]We discovered an uncharted Reef in Fiji also. Fortunately, it was a light bump before we turned quickly to port.[/font][/font][/font][/font][/font][/font][font=inherit][/font]
[/font][/font][font=inherit][font=inherit][font=inherit][font=inherit]Anne Lloyd[/font] [font=inherit][font=inherit][font=inherit][font=inherit][font=inherit]we were stuck for 12 hours[/font]
[font=inherit]Near run thing I can tell you[/font][/font][/font][/font][/font][/font][font=inherit][/font]
[font=inherit][font=inherit][font=inherit][font=inherit][font=inherit]Linda Lane Thornton[/font] [font=inherit][font=inherit][font=inherit][font=inherit][font=inherit]One of the cafes in Neiafu in Tonga used to issue a list of uncharted reefs to yachts heading west and south, most of them known only because people had hit them.[/font][/font][/font][/font][/font][/font][font=inherit][/font]
[/font][/font][/font][font=inherit][font=inherit][font=inherit][font=inherit][font=inherit]Julia Freeland[/font] [font=inherit][font=inherit][font=inherit][font=inherit][font=inherit]Tanda Malika just ran into the reef in Huahini. The reef is not unchartered. It was nothing to do with Navionics.[/font][/font][/font][/font][/font][/font][font=inherit][/font]
[/font][/font][font=inherit][font=inherit][font=inherit][font=inherit]Neil Langford[/font] [font=inherit][font=inherit][font=inherit][font=inherit][font=inherit]Julia, please read the complete analysis - on Navionics Sonar charts the reef was well out of place and completely mis-represented. True, I would not have been there at night, so close, but the Navionics Sonar Charts were completely wrong. That is what this tory is about.[/font][/font][/font][/font][/font][/font][font=inherit][/font]
[/font][/font][font=inherit][font=inherit][font=inherit][font=inherit]Julia Freeland[/font] [font=inherit][font=inherit][font=inherit][font=inherit][font=inherit]Neil...we are in the place they hit the reef!!!! It's a mile wide and on every chart...look at Charlie's Charts![/font][/font][/font][/font][/font][/font][font=inherit][/font]
[/font][font=inherit][font=inherit][font=inherit][font=inherit][font=inherit]Julia Freeland[/font] [font=inherit][font=inherit][font=inherit][font=inherit][font=inherit][font=inherit]We are currently in the lagoon where Tanda Malika hit...the boat is stripped and sitting in someone's garden after been dragged off the reef. Huahini has a fringing reef that is easily seen on all charts. The pass is 6 miles north of where they hit. Th[/font][/font]...See more[/font][/font][/font][/font][/font][font=inherit][/font]
[/font][/font][/font][font=inherit][font=inherit][font=inherit][font=inherit][font=inherit]Alan Leslie[/font] [font=inherit][font=inherit][font=inherit][font=inherit][font=inherit]And a sensible seaman would time the passage so as not to arrive in the dark. Its hard to understand why he chose to arrive at night. The reef is huge and he should have known it was there, some things don;t add up in this story.[/font][/font][/font][/font][/font][/font][/font][/font][/font][font=inherit][font=inherit]

[font=inherit][font=inherit][font=inherit]Neil Langford[/font] [font=inherit][font=inherit][font=inherit][font=inherit][font=inherit]It's fair to say that most of us would not have planned a close pass by that reef at night, hoever[/font][/font][/font][/font][/font][/font][/font][/font][/font][font=inherit][font=inherit]

[font=inherit][font=inherit][font=inherit]Neil Langford[/font] [font=inherit][font=inherit][font=inherit][font=inherit][font=inherit][font=inherit]Oops finger trouble ..... however, if you follow that sad story all the way through you'll see that very large (gross) errors in the Navionics Sonar charts were identified by Evans Starzinger. If they used those bad charts then they simply had to hit t[/font][/font][font=inherit][font=inherit][font=inherit]he reef. Our own little collision was related to an entire reef being missing on the Sonar Charts, then later we (and other OCC [/font][/font][/font][/font][/font][/font][/font][/font][/font][/font][/font][font=inherit]
[font=inherit][font=inherit]Julia Freeland[/font] [font=inherit][font=inherit][font=inherit][font=inherit][font=inherit]Neil the reef around Huahini is obvious and we'll charted...it's even shown on tourist maps. We are on Huahini now and it couldn't be any more obvious![/font][/font][/font][/font][/font][/font][font=inherit][/font]
[/font][/font][font=inherit][font=inherit][font=inherit][font=inherit]Linda Lane Thornton[/font] [font=inherit][font=inherit][font=inherit][font=inherit][font=inherit]Lucky you! We spent nearly three weeks in the deep bay down on the south west corner of the island - all by ourselves.[/font][/font][/font][/font][/font][/font][font=inherit][/font]
[font=inherit][font=inherit][font=inherit][font=inherit][font=inherit]Anne Lloyd[/font] [font=inherit][font=inherit][font=inherit][font=inherit][font=inherit][font=inherit]I do not have experience of the sonar charts[/font]
[font=inherit]Huahine was quite well charted I thought like most if the French Empire[/font][/font]...See more[/font][/font][/font][/font][/font][font=inherit][/font]
[/font][/font][/font][font=inherit][font=inherit][font=inherit][font=inherit][font=inherit]Odette Hasbun[/font] [font=inherit][font=inherit][font=inherit][font=inherit][font=inherit]For those interested in digital charts for iPad, MaxSea TZ offers raster (“paper”) charts that strictly come from the official sources (SHOM, UKHO, etc). We always cross-check Navionics against MaxSea.[/font][/font][/font][/font][/font][/font][font=inherit][/font]
[font=inherit][font=inherit][font=inherit][font=inherit]Julia Freeland[/font] [font=inherit][font=inherit][font=inherit][font=inherit][font=inherit]Navionics can be so much on the money though. In the Tuamotu atolls we were surprised to find many of the coral bombies in the atolls on the chart! Go figure! We still travelled in good light with one of us on the bowsprint using visual checks, but it was quite amazing how our sightings corollated with the charts.[/font][/font][/font][/font][/font][/font][font=inherit][/font]
[/font][/font][/font][font=inherit][font=inherit][font=inherit][font=inherit]Neil Langford[/font] [font=inherit][font=inherit][font=inherit][font=inherit][font=inherit]Julia, yes I agree it can be onthe money - it was outstanding around Cape May and I went into print about it. However that isn't good enough - it can't simply lose major reefs..... When we pay for nautical charts we are buying knowledge - unfortunately Navionics, with Sonar Charts, have turned that on its head and we pay to give the. Knowledge[/font][/font][/font][/font][/font][/font][font=inherit][/font]
[/font][/font][font=inherit][font=inherit][font=inherit][font=inherit][font=inherit]Alan Leslie[/font] [font=inherit][font=inherit][font=inherit][font=inherit][font=inherit]Its interesting that we hear A LOT of folk talking / complaining about Navionics, but few about C-Map. In any event relying on one source of information is dangerous. We have C-Map on our Furuno Plotters, C-Map, Navionics on Max-Sea laptop and raster, GE2KAP on OpenCPN laptop. I also have Navionics on a tablet but rarely use it. AND I keep my eyes open and look out the window ![/font][/font][/font][/font][/font][/font][font=inherit][/font]
[font=inherit][font=inherit][font=inherit][font=inherit]Odette Hasbun[/font] [font=inherit][font=inherit][font=inherit][font=inherit][font=inherit][font=inherit]We used C-Map from the Guadiana river to the Ionian, i.e., for 18 months. This product is not for us. It is the only charting software we have used that, if you are zoomed out, gives no inkling about numerous obstructions that only show up on large, [/font][/font]...See more[/font][/font][/font][/font][/font][font=inherit][/font]
[font=inherit][font=inherit]Alan Leslie[/font] [font=inherit][font=inherit][font=inherit][font=inherit][font=inherit][font=inherit]My experience is quite the reverse in the South Pacific. I have found C-map to be much better then Navionics in identifying dangers and putting them in view. Maxsea uses either c-map, navionics or raster depending on which chart package you buy...howev[/font][/font]...See more[/font][/font][/font][/font][/font][font=inherit][/font]
[font=inherit][font=inherit][font=inherit][font=inherit]Neil Langford[/font] [font=inherit][font=inherit][font=inherit][font=inherit][font=inherit][font=inherit]Hello Folks, please allow me to (attempt) to bring this discussion back on message. It is about Navionics Sonar Charts. Not C-Map, not the normal Navionics charts. Yes, all the charting systems have errors and gaps around the world, but no others (that[/font][/font]...See more[/font][/font][/font][/font][/font][font=inherit][/font]
[font=inherit][font=inherit]Odette Hasbun[/font] [font=inherit][font=inherit][font=inherit][font=inherit][font=inherit][font=inherit]Neil, we have also come across several errors on Navionics Sonar Charts (NSC). Yet NSC is our primary, because of the wealth of detail and excellent user interface. But because we know of the high error rate on NSC, we do the following:[/font]

[font=inherit]1. Always r[/font][/font][font=inherit][font=inherit][font=inherit]un two other charts to cross-check against Navionics. Currently, MaxSea TZ (raster, official charts) and Imray Navigator (raster, proprietary charts).[/font]

[font=inherit]2. When in doubt, fire up our Garmin Bluechart.[/font]

[font=inherit]3. Avoidance or minimal (i.e., 1 knot or less) speed on any "dotted black line" marked area on Navionics. We understand that "dotted black line" means "questionable." On the Crystal Blues blog, Gangway and Grindstone ledges are shown both inside "dotted black lines."[/font]

[font=inherit]4. ScanForward forward-looking sonar is always on if we enter any questionable grounds. Would not enter any NSC "dotted black line" grounds at any speed without ScanForward, unless with local knowledge.[/font]

[font=inherit]5. Since the last 2 months or so, we also run Ovitalmap for extremely easy, automatic-save satellite imagery to compare against the sources mentioned above when deciding where to anchor.[/font]

[font=inherit]It takes some work to make Navionics Sonar Charts one's primary, but the level of detail and ease of use can't be beat.[/font][/font][/font][/font][/font][/font][/font][/font][font=inherit][/font]

[font=inherit][font=inherit][font=inherit][font=inherit]Neil Langford[/font] [font=inherit][font=inherit][font=inherit][font=inherit][font=inherit]Interesting that you'd go to so much trouble to continue using a faulty product, but good on you for persevering. Your comment about the dashed black line is also interesting, thanks. You may note that the reef / ledge we found and collided with was not circled by a dashed line, so nothing is guaranteed unfortunately.[/font][/font][/font][/font][/font][/font][font=inherit][/font]
[font=inherit][font=inherit][font=inherit]Odette Hasbun[/font] [font=inherit][font=inherit][font=inherit][font=inherit][font=inherit]Well, we have to. We anchor out most of the time, year-round, so the payoff of using the charts with the most detail (Navionics) is being able to anchor in safe, secluded places, often well off the trodden path.[/font][/font][/font][/font][/font][/font][font=inherit][/font]
[font=inherit][font=inherit][font=inherit][font=inherit][font=inherit]Dierdre Atkinson Wogaman[/font] [font=inherit][font=inherit][font=inherit][font=inherit][font=inherit]We used an IPad with governemnt charts in the USA, but purchased Navionics charts for our cruise to the Canadian Maritimes. We have redundant Candian government charts on our laptop. We found good agreement, but don't use the sonar feature, becasue frankly it drives the navigator crazy to look at it. We always treat crowd sourced data with skepticism.[/font][/font][/font][/font][/font][/font][font=inherit][/font]
[/font][/font][/font][font=inherit][font=inherit][font=inherit][font=inherit]Neil Langford[/font] [font=inherit][font=inherit][font=inherit][font=inherit][font=inherit]Hi Dierdre, well put, although in the cases we're discussing here it is not the crowd sourced data that is the problem - its the fact that Navionics simply LOST a ton of perfectly good data that was on the Government charts.[/font][/font][/font][/font][/font][/font][font=inherit][/font]
edited by simoncurrin on 9/27/2017
By Hasbun - 26 Sep 2017

«[font=sans-serif]Have you had experience with inaccuracies on Navionics charts?[/font]»

[ul][li]1. Guadalquivir river, just downstream from Seville: no indication of the overhead power cables existing on the river bypass nor on the city channel into the port.[/li][li]2. Tomás Mestre canal into the Mar Menor near Cartagena: Navionics had a fantasy that the channel was passable only by tender at two separate points. We draw 2.2 meters, went in w/o issue.[/li][li]3. Unnamed cove immediately N of Akra Khondri Pounda, N of Frikes, Ithaca (alternate description: second cove S from Agios Nikólaos Is.). Where Navionics says there are 28 ft., in reality there are 148 ft.[/li][/ul]
The first one, we reported, got a quick reply, and within two weeks our chartset had been updated to accurately include both sets of power cables. The other two, we haven't reported.

Navionics charts are our primary navigation tool because of the richness of detail, wealth of ancillary information, and ease of use. However, we don't trust Navionics more than we need to, and we cross check them against a _minimum_ of two other chartsets (currently, MaxSea TZ and Imray Navigator), sometimes three, plus satellite imagery from Ovitalmap for anchorages, plus forward-looking sonar at very, very slow speed when doubts still remain.
edited by Hasbun on 9/26/2017
edited by Hasbun on 9/26/2017
By simoncurrin - 14 Oct 2017

More on the topic of Navionics inaccuracies
By DariaBlackwell - 7 Dec 2017

More here: http://www.twoatsea.com/navionics-sonarchart-problem/ Nice analysis.