Navionics - A Childrens Toy?

[carstenb]

hi all,

I just purchased a Raymarine Axiom Pro12 RVX with Navionics charts of all North America bundled in. These are Navionics+ charts and according to Navionics websie - they are a real sailing set of charts not just overview. (es I do know not to trust them for navigation etc). We'll be sailing the Pacific side of North America for the next year or so.

Getting ready to sail from Hilo to Maui - I checked the depth in Lahaina harbor.

Hmm - 0.4 meters

My OPEN CPN says 2.7 meters (basically this is C-Map)
My MaxSea says 2.7 meters (Maxsea is also C-Map)

Go on-line with Navionics support - yeah - you need to load their Sonar charts to get the correct depth.

soSonar charts? Ok I downloaded it - now it says the depth is 0.9 meters and my entire plotter screen is filled with depth contour lines because the Sonar Charts show 1 foot differences

This really isn't on - call Navionics support and spend a loooong time getting their support person to understand.

She says - try looking at the chart viewer - you probably have an old chart that needs updating. Old Chart? Lahaina harbor has been there for a century.

Look at the viewer - this says 1.3 meters
So now we have 3 Navionics products all showing different depths in the same harbor. I ran my dinghy in there and the water is somewhere between 1.5 and 3 meters.

The support person told me that the 0.9 came from a community edit where someone had run their sonar while i the harbor and uploaded the data. The guy who did that probably had the sonar setting set for depth below his keel.

Support finally tells me she will kick this problem up to their chartology department.

BTW - checked on NOAA - their chart says 1.4 meters

So If Navionics gets it this wrong on an old well-established harbor - what else is wrong?

Anybody have have nay suggestions? Or should I just chuck Navionics and buy C-Map?

[mikedefieslife]

From you post Navionics, NOAA, and C-map are all different. Why would you buy C-map over Navionics it is also different from NOAA which you'd like to presume is official?

Also depending on the screens you are looking at Navionics can the current depth for the time of tide, rather than the mean low water depths. Also all community edits can be turned off.

Any way to check what Garmin has for that area, I wonder if that too is different. Which one do you trust?

[El Pinguino]

My 'burgle brand' CM93 shows 2.1 in the entrance, 2.4/2.7 further in.

Now that cartography is what? 20 years old? Has there been silting or shoaling since then? How old is the NOAA data?

[CassidyNZ]

Originally Posted by carstenb

soSonar charts? Ok I downloaded it - now it says the depth is 0.9 meters and my entire plotter screen is filled with depth contour lines because the Sonar Charts show 1 foot differences

Maybe I’m missing something important but . . . .

On my Navionics I click the light blue icon (middle icon, lower left) then select “Sonar chart”. Then click Menu - Map options. Scroll down to SonarChart Density and use the slide to change the density of contour lines.

Perhaps you’ve tried this and it doesn’t work very well?

There are places I’ve sailed (e.g. Fiji) where Navionics was less than adequate but then so where other systems and paper charts. Where I live Navionics is pretty good.

[requiem]

Originally Posted by El Pinguino

My 'burgle brand' CM93 shows 2.1 in the entrance, 2.4/2.7 further in.

Now that cartography is what? 20 years old? Has there been silting or shoaling since then? How old is the NOAA data?

From the NOAA chart I just pulled, the survey was done in the 1960s. The zone of confidence is B, meaning the depths should be accurate to within a meter. Positions should be accurate to within 50 m, but since we're talking about inside the harbor I think they're not that bad.

[carstenb]

Originally Posted by CassidyNZ

Maybe I’m missing something important but . . . .

On my Navionics I click the light blue icon (middle icon, lower left) then select “Sonar chart”. Then click Menu - Map options. Scroll down to SonarChart Density and use the slide to change the density of contour lines.

Perhaps you’ve tried this and it doesn’t work very well?

There are places I’ve sailed (e.g. Fiji) where Navionics was less than adequate but then so where other systems and paper charts. Where I live Navionics is pretty good.

I treid the density option but as soon as you move from High density to medium density the depth goes to 0.4 meters

[carstenb]

Originally Posted by mikedefieslife

From you post Navionics, NOAA, and C-map are all different. Why would you buy C-map over Navionics it is also different from NOAA which you'd like to presume is official?

Also depending on the screens you are looking at Navionics can the current depth for the time of tide, rather than the mean low water depths. Also all community edits can be turned off.

Any way to check what Garmin has for that area, I wonder if that too is different. Which one do you trust?

Navionics show current depth at time of tide? That would be a completely new thing.

But the standard for charts is to show depth at Lowest Astronomical tide so if Navionics is showing it at current tide time - the depth should be higher, not lower than C-Map, MaxSea etc.

[Nanamuk]

Here in the PNW Navionics has enough errors that I don't trust it for anything important. We have found large areas with big depth discrepancies, small islands that are missing and rocks that either aren't charted or are charted but don't exist. We do use it to monitor course deviation due to current but otherwise rely on paper charts, our eyes, the depth sounder and sail a strong boat that can withstand the occasional bump.

[nortonscove]

Originally Posted by mikedefieslife

From you post Navionics, NOAA, and C-map are all different. Why would you buy C-map over Navionics it is also different from NOAA which you'd like to presume is official?

Also depending on the screens you are looking at Navionics can the current depth for the time of tide, rather than the mean low water depths. Also all community edits can be turned off.

Any way to check what Garmin has for that area, I wonder if that too is different. Which one do you trust?

It's my understanding that they are the same now. This according to my last contact with the company.

[chasmains]

Hi folks,
I’m a lot surprised that someone trusts any info source that predicts depths less than a meter. That’s plus or minus 19 inches to us SAE guys and really a small tolerance in an ocean water environment. The water depth varies continuously everywhere, all day, every day. And with currents, wind and propellers passing by all the time these depths can’t be trusted to be true as shown on any chart or software package. When I’m out there, measured depth beneath the keel is the truth at that moment. Don’t believe anything you read.

[beirutsailor]

You may be forgiven to think that showing less depth is not dangerous. But.
During a force 6 warning in Lakka bay on Paxos, I noticed boats crowding an exposed and weedy part of the anchorage, avoiding a protected one with good sand holding. My, and I suppose, their Navionic maps read 0.4, while my Garmin showed 2.8m, confirmed by actual sounding. So I anchored safely watching the mayhem of dragging anchors during the night.

[requiem]

Originally Posted by El Pinguino

My 'burgle brand' CM93 shows 2.1 in the entrance, 2.4/2.7 further in.

Following up on my other comment, your CM93 shows identical to current NOAA ENC data. I pulled the NOAA raster chart just for kicks, it shows 1 fthm, 2 or 3 feet in the same spot; so effectively the same as well.

Originally Posted by chasmains

I’m a lot surprised that someone trusts any info source that predicts depths less than a meter. That’s plus or minus 19 inches to us SAE guys and really a small tolerance in an ocean water environment.

The charts do indicate the tolerances, but I suspect few actually look.

[chasmains]

Hi Requiem, I know charts and tide tables and other sources provide tolerances,. They only provide average depths and average tolerances at the times of their surveys. But I’m referring to the continuous depth variabilities of dynamic environment action. The bottom moves around all the time in places where waves, currents, winds and the occasional propeller pushes it. In shallow water, charts and software can’t be relied on. Only caution.
Thanks, C

[Breaking Waves]

Originally Posted by carstenb

I treid the density option but as soon as you move from High density to medium density the depth goes to 0.4 meters

This is what I see on Navionics - are you seeing something different?



The noaa chart I have is not much help (I don't see an official harbor chartlet/survey - is there one).



ah, I see this but the details are pretty sketchy

[wrwakefield]

Carstenb,

We primarily use Navionics+ in our two B&G Zeus2 chart plotters plying South-Central and Southeast Alaska waters.

We update when we can [typically every few months] and find the charts to be accurate in most instances. On occasions where someting is missing [or only exists on the chart...] I cross reference against NOAA raster charts and often- but not always- find a similar error.

On edit: I should note we rarely use or trust the Navionics 'SONAR' chart info. Currently there seems to be too much interpolation [in our area anyways...] to trust our boat to it...

We also use C-Map charts, [with our two plotters with 2 SD card slots each, we can currently use 4 seperate chart sources on each...] Sometimes I run Navionics and C-Map splitscreen [side-by-side, same scale] when transiting tricky waters for the first time. [e.g., Keku Straight AKA Rocky Pass...] to determine which is best-of-breed for that area.

The reason for having both Navionics and C-Map is I have found over time that sometimes Navionics has better detail, and other times C-Map excels. Oftimes they are close to the same. [We reinforced this to ourselves while scrutinizing/planning routes and anchorages through the NW Passage— though we have not transited those waters yet...]

Most of the time when one chart source lacks detail, the other makes up for it, so Navionics/ C-Map is a good combimation for us.

As a hedge, we always have NOAA raster charts running in SeaIQ on a tablet, and available on Open CPN on a laptop. We cross compare frequently [there is a tablet next to each chart plotter at both helms...] and feel this is necessary to continue successfully missing the hard bits around the edges up here... [Forwars facing SONAR is very useful in these waters...]

We will truly miss the raster charts should NOAA follow through and deprecate them as currently being discussed.

I hope some of this is useful for you.

Cheers! Bill

PS: We typically overlay RADAR on the chart[s] to confirm chart accuracy. We rarely note any discrepencies.

PPS: It is important for other readers to note we are not talking about the Navionics app running on portable devices. My comments pertain to Navionics+ charts run on a chartplotter. [MFD]