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Lack of depth soundings in blue shaded areas in Garmin g2 BlueChart 2010

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Lack of depth soundings in blue shaded areas in Garmin g2 BlueChart 2010

Old 05-19-2010, 06:08 AM
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Default Lack of depth soundings in blue shaded areas in Garmin g2 BlueChart 2010

I'm a long time Garmin user. I've bought two Garmin iQue 3600s, GPSMAP492 and two other Garmin chartplotters plus four handheld GPS. I've been a happy customer and so when the g2 BlueChart update for March 2010 came out, I bought a copy for my 492. Unfortunately, I've found that the spot soundings have been severely cut back ("decluttered" was the term used by the Garmin technician I spent an hour on the phone with last tonight). Fewer spot soundings are fine in the "white" deep areas but Garmin has also cut back severely in the blue, shallow areas! Those are the areas where I anchor and for me it makes the g2 Mar 2010 update unusable. In some cases, all the soundings in a blue shaded area have been deleted (zippo, no depth soundings at all). What do you make of that when you're trying to anchor your boat?

Apparently the Garmin algorithm for "thinning out" the spot soundings needs some fine tuning. Fewer spot soundings in deep areas are fine, fewer spot soundings in shallow areas are not. I've included a pdf file with examples comparing the display of g2 Mar 2010 vs the built-in g2 version 3.50 that came with a the 492. There is a vast difference.

You can look over the attachment and compare the two charts shown side by side. Which one you would want to see when coming into an unfamiliar anchorage? There's no setting in the 492 to turn off the "decluttering" effect.

Is anyone else bothered by this "decluttering" effect?

Last edited by bob423; 05-25-2010 at 04:24 PM. Reason: Fixed broken link to pdf
Old 05-19-2010, 07:56 AM
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Do you get any more detailed soundings when you zoom in?
Old 05-19-2010, 08:14 AM
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marccoop,

No. Even when I zoom in to 120ft, no additional soundings appear. Very disappointing.

I'll also add that the map detail tab is set to "Most". The only change between the two screen shots is deselecting the use of the g2 Mar 2010 card.

Last edited by bob423; 05-19-2010 at 08:36 AM. Reason: more info
Old 05-19-2010, 12:01 PM
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Do you have SPOT SOUNDINGS turned on? And, do you have it in "Fishing Chart" mode or "Navigation mode", if that units has those choices....?

My new 2010 G2 Vision card has the same detail of spot soundings on it.
Old 05-19-2010, 12:10 PM
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that sucks, as little detail as the base map the cheap units come with. I guess I'm lucky I got the Bluechart the year before the G2 edition came out....
Old 05-19-2010, 01:37 PM
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Default Birdman Reply

Birdman,

Yes, spot soundings is turned on. The 492 doesn't have a "fishing mode" or "navigation mode". It's one mode for all.

Questions:
- When you say that your 2010 g2 vision card has the same level of detail does that mean it has the same number of spot soundings as I show in the examples for my g2 2010 card or for the previous g2 version that was built into the 492 (v 3.50)?

- What chartplotter do you have?

- Since the Lat and Long are displayed in the photos, an exact match to the location can be made for comparison, I'd be interested in your results.
Old 05-20-2010, 05:49 AM
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I looked at your pdf. Agree it's annoying to have lost the soundings. But realize that those soundings are 1)probably many years old, 2)subject to an ever changing bottom contour and 3)not the only way to determine depth. I'm not going to justify the change that Garmin made here, and I'd like as much information at my disposal as possible too, but here's the awful truth--all those soundings are fiction. They are not the actual depths, they are an approximation that was true at the time the soundings were taken--perhaps decades ago. The contour lines provide some help, too. With a 10 foot sounding in one contour area, and a 20 foot sounding in another, you can tell what the approximate depth is by observing the contour line boundaries. With no soundings in a contour area, you are left to guess. But your boat has a depth sounder, doesn't it? And you have paper charts on board, right? Use them for the detail reference, as you should never rely on a single source of data for any navigational task.

I guess the point is this. Yeah, the loss of data is unappealing. But it's not a hazard to navigation and shouldn't change your responsibility to review the paper chart and your boat's depth sounder to pick an anchorage.
Old 05-20-2010, 07:48 AM
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Bob,
Couple things: First, I jsut realized you are writing "G2 Version", and NOT "G2 Vision", which I had originally thought. So scratch my first post as I was referring and thought you were, to the new G2 VISION charts.

That said, Garmin has nothing to do with those "spot soundings". As the previous postermentioned, most of those are very old anyway. If the US Geo dept feels the spot sounds are no longer valid for whatever reason, they either remove them, or change them, and sometiems just block them out (as is done in fast chaning area's like inlets). So that is probably the case with what you are seeing. An easy way to check this is, find the latest paper charts for the same area, and see if they spot soundings are also gone from that, I bet they are.

That's my best guess anyway.
Old 05-20-2010, 06:43 PM
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Default Buoy Scout

Interesting post:

Your points:
1)probably many years old
I take your meaning to be that if the sounding is old, then it's not accurate? I've spent many summers cruising Maine, anchoring out in many remote coves and I've found the soundings to be very accurate and not subject to change year to year. I've found the same results in Long Island Sound and also in the Caribbean (BVI, St. Vincent, St. Martin) Perhaps in your cruising area the conditions are different. I would prefer to make my own decisions about use or non-use of a bottom sounding and not have it arbitrarily censored by a program algorithm for decluttering the screen.
2)subject to an ever changing bottom contour
See above.
3)not the only way to determine depth
I'll assume your comment is not condescending since we've in a polite forum so I'll explain my setup. I have a Beneteau 423 sailboat with a Spade 45 lb anchor. I spend four months of every year cruising (Maine, Long Island Sound), I anchor out about 80% of the time so I've become very familiar the my anchor and depth readings. I prefer to take into account all information available to me and resent any censoring of information that I could find useful (e.g., depth soundings).

There are additional comments which sure do sound condescending but I'm sure you didn't mean them that way. Do I have paper charts? Yes but the charts I mainly use other than those on the Garmin chartplotter are the digital charts downloaded from the NOAA site since they are kept up to date and are much easier to store.

Let's maintain focus on the subject of the post - lack of depth soundings in the new Garmin g2 Mar 2010 update - and whether you think that's a good idea or not.
Old 05-20-2010, 06:56 PM
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Default Birdman Reply

That said, Garmin has nothing to do with those "spot soundings".
Garmin uses a mapping service. Perhaps it's not Garmin itself but they have a cartography department which I've complained to.

An easy way to check this is, find the latest paper charts for the same area, and see if they spot soundings are also gone from that, I bet they are
This is an excellent idea! As backup for the Garmin 492 charts, I've have a download of all the NOAA charts for the East Coast. The advantage here is that NOAA updates the charts as they change so a download gives you an updated set. I found the identical area for each of the examples I gave in the pdf and, guess what, they all have the same depth soundings as the Garmin g2 V3.50 charts, the internal charts of the 492. The Garmin g2 Mar 2010 charts are censored (my term) or decluttered (their term) for spot soundings by some algorithm. The problem is that the algorithm someone came up with doesn't allow (apparently) for non-decluttered areas of interest (shallows or where you might want to anchor).

I've updated the pdf file to include an excerpt from the NOAA chart of the same area.

Last edited by bob423; 05-25-2010 at 04:24 PM. Reason: fixed broken link
Old 05-21-2010, 04:56 AM
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Originally Posted by bob423 View Post
........ I would prefer to make my own decisions about use or non-use of a bottom sounding and not have it arbitrarily censored by a program algorithm for decluttering the screen.
................
But what about the person who sees that there's supposed to be ten feet of water but finds only three feet and capsizes the boat with loss of life? Who is he going to blame (sue)?

If it's not pretty well guaranteed to be accurate, it's better for it not to be shown.

And yes, I know about all the warnings and the statement you have to agree to, but just like a boat, you don't have to be smart or have common sense to buy a plotter, you just need a credit card.

Just let me add; While depths may not change in some areas, sections ot the ICW (for example) constantly shoal and are constantly dredged so there's no way a chart (paper or electronic) is going to be accurate.
Old 05-21-2010, 08:04 AM
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Default rwidman

You make some good points:

But what about the person who sees that there's supposed to be ten feet of water but finds only three feet and capsizes the boat with loss of life? Who is he going to blame (sue)?
If the charts are nothing more than reproductions of the NOAA charts for the same area, then it's pretty straightforward - sue the government - which of course you can't. If the charts are altered from the NOAA charts and that alteration causes a boat to run aground, then the boater may have a case, regardless of all the disclaimers in the initial screen of the chartplotter. The version 3.50 g2 charts appears to be just that, a direct copy of the NOAA charts. I believe Garmin may have some risk with their g2 Mar 2010 charts (as they apparently believed they did with the 2009 version which they recalled after several running aground incidents as reported elsewhere in this forum)

If it's not pretty well guaranteed to be accurate, it's better for it not to be shown
If Garmin just repackages the NOAA charts and includes all the information on those charts (e.g., all depth soundings), then how can Garmin be blamed for a problem? If they start deleting info, then that's a slippery slope.

Just let me add; While depths may not change in some areas, sections of the ICW (for example) constantly shoal and are constantly dredged so there's no way a chart (paper or electronic) is going to be accurate.
Very good point. In areas where shoaling occurs, then any paper or electronic chart is of little use in predicting depth on a course. Other resources are required such as Cruisers Net or local sources (Seatow or BoatUS).

However, regardless of the shortcomings of NOAA charts, I would think that the best strategy for Garmin would be to just reproduce them on their chartplotter - without editing out information at zoom levels used for anchoring or navigating narrow channels.

All I want are the NOAA charts on my chartplotter. I want to be the one to make the decision to use or not use depth soundings. I do not want some programmer with a "decluttering" algorithm written to some unknown criteria to make that decision for me. Is this too much to ask?
Old 05-23-2010, 04:54 PM
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No condescension intended. But I see you are sure passionate about this issue. I don't see it as such a big problem, but obviously you do. I guess the solution is to get a different chart plotter with different charts? Or just refer to your paper charts as needed.
Old 05-23-2010, 07:07 PM
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Default Buoy Scout

The passion comes from all the anchoring out I do and the desire to have all the depth information on the NOAA charts available at the helm on my chartplotter as I find a spot for the night. If I didn't anchor out much, I wouldn't care. As to other companies, it's unclear whether they may suffer the same fate if their charting source is the same. Interesting to pursue. Perhaps the other companies have other sources that will bypass this issue.

It just seems a shame to see a fine company such as Garmin take a step backwards. It begs the question, "What were they thinking?"

I can always fall back on my downloaded digital charts from NOAA but the convenience of having them available (via the 492) right at the helm with boat position shown is lost.
Old 05-23-2010, 09:20 PM
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bob

After looking at your .pdf's, I totally agree. This is disgraceful. You have just saved me a few bucks (quite a few) for the upgrade I was getting ready to order. Now I won't without having a look at West or somewhere to see what our local area looks like. I am in the Keys and all the areas where I really need/use the plotter for navigation (as opposed to finding a spot) are very, very shoal. The old Garmin blue chart G2 charts (my built-in) are very good in regard to the number of sounding spots, etc. If the new ones are similar in our area to how they are in yours, no go.

Garmin has been dropping the cartographic ball more and more the past 18 months to two years, IMO, and it will be interesting to see if they can get their mojo back. And if it's their cartography partner, maybe it's time for a new partner.
Old 05-24-2010, 04:55 AM
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Default KeyPineSavage

I'm starting to get some interest out of Garmin judging from a few notes I've received back. Sitting here at my desk with the 492 at my side, I could easily add a few more areas to the pdf. If you're interested, I can add some snapshots around Key West. All I would need would be the Lat, Long or the names of the channels or anchorages.
Old 05-24-2010, 08:23 PM
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bob

Sure. Maybe for everybody, it's best you keep showing the two side by side. For me, I've got a 498 with the same built-ins that your 492 has so I don't really need the older ones, but do either .

As far as where, the area I know best, and would be most interested in, would be along the northeast side of Big Pine Key, about 35 miles ENE of KW. If you look, you will see both the Bogie Channel separating Big Pine and No Name Keys, and NE of that Big Spanish Channel, which runs all the way from the Atlantic near Bahia Honda Key and Bahia Honda Channel northwest to the Gulf. Anywhere in some of the shoal areas in that region or actually also along the Atlantic shores of any of those islands.

As said, I'm sure not liking what I'm seeing in your .pdf's so far.
Old 05-24-2010, 08:43 PM
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Not very good looking maps, before or after

Spot soundings are not "fiction". A small fraction of soundings in areas that shoal will change, but more is always better than less. NOAAs data was put where it is on paper for a reason. Yeah, they can be old, but they are usually pretty accurate.

There are other sources for more accurate and current data that other catrography companies use to improve accuracy.

There is no such thing as too much information on a navigation chart (however, being able to display only what you need should be an option on a vector chart).

I agree, unless there are more zoom levels, they goofed on the de-clutter algorithm.
Old 05-25-2010, 08:58 AM
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Originally Posted by Jeff@Navionics View Post
A small fraction of soundings in areas that shoal will change, but more is always better than less.

I could NOT disagree with that more!! Ask the local LI prop shop Bossler and Sweezy how accurate the charts with Spot soundings I'm using are!!! Last year I ran aground because of faulty old "spot soundings". The sounding showed 6' of water, it ended up being 6" of water. If they had left the spot soundings out, I would not have attempted to make the passing. If you turned spot soundings off in that area, there were no depth markings because they know they change to often. So the spot soundings gave me a false sense of security.

Lesson was learned, and prop re-conditioning costs were figured in.

Keep in mind, I'm not defending Garmin in this case. I'm not sure if the "error" in this case posted above is good or bad. In my area, all the spot sounding are there in the latest chip update, so I don't see that problem at all.

But I do disagree that "more is always better" on charts. That is clearly NOT the case, and the reason NOAA leaves many changing area's blank on all it's charts.
Old 05-25-2010, 09:46 AM
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Default Comments on decluttering

Birdman, I now understand your position much better. Nothing like having a chart tell a lie and cost you lots of money to lose faith in charting.

However, I have no argument with NOAA leaving spot soundings off per their judgment in how reliable they are. I do have an argument with some algorithm censoring spot soundings to less than NOAA standards. NOAA I trust, an algorithm written by some unknown programmer to some unknown criteria I do not trust.

In my view, chart software that reproduces the NOAA chart is the gold standard, at least 500ft to 120ft zoom levels. Where a spot sounding algorithm is really needed is when the lower zoom levels are used (e.g., 1.2nm, 0.5nm, 0.2nm, etc.) where there is just not enough room on a 5" display to show all the chart detail. Even then, the algorithm has to be smart enough to always show the minimum depth spot soundings in the field of view and all hazards - so the algorithm has to be fairly sophisticated. In the case we've been talking about, the algorithm hasn't been debugged properly for high zoom levels in shallow areas.

This problem of too much information to be displayed (and therefore the creation of a decluttering algorithm) is common to all vector charting. This is because displayed information such as spot soundings is kept at a size that can be read (some constant minimum size) and so as the area to be displayed is increased - the display just runs out of LCD pixels and an algorithm has to decide what gets priority for display. Bigger displays just move the problem to a lower zoom level (e.g., 0.8 nm instead of 0.3nm).

What has happened in Garmin's case is they've let the decluttering algorithm operate at zoom levels where it's not needed, e.g., 500 to 120ft. At the very least the density of spot soundings should be a selectable value on the map tab in the chartplotter ("Most, more, normal, etc.) Or, perhaps Garmin is trying to save space on the chip with fewer spot soundings? That's hard to believe in this day of cheap memory but perhaps every cent counts.

Since I'm starting to see some interest out of Garmin, I plan on going back to the pdf and add a section on number of spot soundings in the field of view for each of the examples. I'm trying to help the Garmin techs argue with their cartography department and numbers work better than pictures (pictures are nice for examples but numbers drive the point home).

Finally, I'll also add examples as suggested for the Key West area.

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