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Author Topic:   Chart Data: The Good of the Commons
jimh posted 11-02-2012 10:13 AM ET (US)   Profile for jimh   Send Email to jimh  
As the world wide web has shown us, freely sharing data among a large group tends to work well, and this open exchange of information results in a general good for the commons. In digital chart cartography we are at the beginning of a new era in which we may see the same sort of open sharing of information result in a general benefit or good for the commons.

With modern boat electronics, computers, and communication networks, it is now entirely possible for individual boaters to record depth and position information as they are boating with rather high accuracy, in effect turning thousands of boaters into chart surveyors. The recorded data could be submitted in electronic form to a centralized collection point. If the data from thousands of boaters' on-the-water measurements of depth and position could be collected, organized, and published in a useful manner, it would be possible to produce more detailed and more up-to-date navigation charts, or to create charts for areas where no charts previously were available.

At least one major publisher of digital chart cartography is considering introducing a program or method by which users of their charts could participate in a process of continually updating and improving the chart data by submitting their own survey data from their own boating trips. The data would then be added to the published charts, and provided to owners of the published charts as updates, either for free or for a nominal cost.

NAVIONICS has just recently announced their SonarCharts program. See

for details. This program will implement a system of collection and organization of user SONAR data to update existing Navionics charts.

6992WHALER posted 11-02-2012 04:06 PM ET (US)     Profile for 6992WHALER  Send Email to 6992WHALER     
Interesting, I just glanced at the link.

The first thing that comes to my mind is how much discrepancy there is in transducer placement. No one has a transducer mounted even with the surface. Many are several inches if not feet under water. How do you get accurate data when you do not control the equipment?

K Albus posted 11-02-2012 04:30 PM ET (US)     Profile for K Albus  Send Email to K Albus     
Also, everybody mounts their GPS antenna in a different spot, and the vast majority of them are not mounted directly above the sonar transducer.
David Pendleton posted 11-02-2012 05:59 PM ET (US)     Profile for David Pendleton  Send Email to David Pendleton     
I thought the same thing as well. Maybe they average the data received but that would only work well for heavily-surveyed areas.

I don't get it. Why aren't we using existing bathymetric satellites for this stuff?

Chuck Tribolet posted 11-02-2012 10:19 PM ET (US)     Profile for Chuck Tribolet  Send Email to Chuck Tribolet     
AFAIK, no such thing as a "bathymetric satellite". RADAR
doesn't penetrate water worth a damn. There's no substitute
for "mowing the lawn" with a high resolution SONAR.

In most areas, it won't matter that the GPS is 10' from the
transducer. It's close enough.

And all three of the SONARs I've had have allowed the input
of an offset from surface to transducer.

I suspect this won't generate a lot of new info in the USA,
but in other areas (third world) where there's no NOAA and no
USGS, it could be important.

I hope they find a way flag the areas with NO data. That will
turn to be areas where local knowledge says there's a rock in


David Pendleton posted 11-02-2012 11:11 PM ET (US)     Profile for David Pendleton  Send Email to David Pendleton     

[Please start a new thread to begin discussing aerial or satellite tecniques for depth measurement; thank you--jimh.]

jimh posted 11-03-2012 05:33 AM ET (US)     Profile for jimh  Send Email to jimh     
In the Navionics SonarChart method the user-gathered data about water depth will be presented in a separate chart layer of information. You can suppress that layer of information from being presented, if you wish.

To the issue of the accuracy of the user provided data, I agree with those who have commented about the potential for position errors and depth measurement errors to be present in the data. How this will be handled by the SonarChart program is not clear to me.

At the same time as the Navionics SonarChart program is being launched, Lowrance has announced it will be providing to users of their devices an option to create customized charts from the user's own SONAR data. Lowrance calls their program Insight Genesis. They are offering to convert data collected by an individual into a customized chart for that individual and for a fee. This program has several important differences from SonarChart.

First, Insight Genesis appears to be isolated to individuals. If I happen to collect great data about my favorite watery parts of the world, the conversion of this data to a useful Insight Genesis chart is only going to happen for me, and, I have to pay Lowrance a fee to combine my data into the chart Insight cartography in my Lowrance device. The fee ranges from $20-per-update or annual subscriptions sold in tiers at $100 to $300 per year.

The Lowrance method appears to not really contribute to the good of the commons, and can also be expensive. The Navionics method seems to provide for a sharing of data across many users, and does not seem to involve a great deal of fees, other than having to purchase the initial package of the Navionics cartography to use as the base map. It will be interesting to see which approach takes off and becomes more popular.

More sophisticated users of SONAR and digital cartography have already had the option of making their own charts using software such as DrDepth. After a one-time fee to purchase the software, users can collect SONAR data and make their own maps with the software. DrDepth presently has the ability to create maps for viewing on various non-SONAR devices, such as a computer or an iOS device. It appears to also be able to create maps that can be used with certain Lowrance SONAR and chart plotter devices, but I believe the maps are not integrated with other cartography, that is, they become separate charts and not overlays or add-on's to existing charts.

jimh posted 11-03-2012 06:15 AM ET (US)     Profile for jimh  Send Email to jimh     
A concern I have with the adding of data to existing charts is the integrity and preservation of the original chart data file. Typically the chart data on a chart plotter is copy protected and kept in an encrypted file. If the integrity of this file is lost, replacement of the file is usually not a simple, trivial, or free process. In the case of files stored on internal memory, say the file on my Lowrance HDS that provides the Insight base map, the whole unit would probably have to be returned to the factory to have that file reinstalled. This is because Lowrance would most likely not want to send out the data for a user to install. That would let the cat out of the bag, so to say.

If the user-data is to be integrated into the base map of a copy-protected and encrypted file, it seems like a risky process to let the user make this patch. If anything goes wrong, the user is going to be upset and the service provider will have to make a remedy.

I suspect that the user-added data might be segregated to a separate file, and the data combined with the base map in a manner accomplished in some crafty process in software. That would preserve the integrity of the copy-protected base map file.

Jefecinco posted 11-03-2012 09:42 AM ET (US)     Profile for Jefecinco  Send Email to Jefecinco     
I fish uncharted waters for the most part. This is particularly daunting in Little Lagoon in Gulf Shores, Alabama. I tend to watch other boats and make GPS tracks to help me move around the lagoon safely.

It would be highly useful to have software embedded in my MFD that would input sonar data to my chart data on demand and remember it. If that was the case, over time I could have a workable chart of Little Lagoon and several other areas in which I fish. I could share my data with others via a data card if the MFD software was compatible.

Tidal information and time of day is now present in the software so that variable could be included in the "Add Data" feature.

Perhaps the feature is available in upper tier electronics. If so, I hope it trickles down quickly. When my Boston Whaler boat with engine and trailer cost $4000 it seem almost ridiculous to imagine paying $3000 plus for a fully featured MFD.


L H G posted 11-03-2012 01:16 PM ET (US)     Profile for L H G    
Then there are tides, tidal surges based on even light wind, constantly fluctuating Great Lakes seasonal levels, seiche effects, reservoir flowage heights, river flows, rainfall, etc. Sounds like a stupid idea to me.
jimh posted 11-03-2012 03:12 PM ET (US)     Profile for jimh  Send Email to jimh     
Larry--That's what a lot of people said--"sounds like a stupid idea"--about hypertext and the HTTPD protocol when it was first shown to them.
David Pendleton posted 11-03-2012 03:52 PM ET (US)     Profile for David Pendleton  Send Email to David Pendleton     
I wish they'd do something like this for the Mississippi River; USACE charts do not have soundings on them at all.
Jefecinco posted 11-03-2012 06:28 PM ET (US)     Profile for Jefecinco  Send Email to Jefecinco     

My last assignment in the Army was to the Navigation Section of a USACE District. One of my first questions to the staff was why there were no depths indicated on the river charts we sold.

I was told that the only time accurate depths for the rivers were available was immediately after dredging operations. The rivers flow so fast and carry so much dirt which settles where it wants that it would require constant surveys and updates to even approximate accurate readings.



David Pendleton posted 11-03-2012 06:35 PM ET (US)     Profile for David Pendleton  Send Email to David Pendleton     
There are a lot of places I'd like to gunkhole, but I'm afraid to because I have no idea how deep the water. Toss in stump fields and wing-dams (which are charted, sort-of) and it can be a little daunting.

As long as they keep the channel at nine feet...

jimh posted 11-04-2012 03:31 PM ET (US)     Profile for jimh  Send Email to jimh     
I can dismiss all of Larry's arguments in one word: timeliness. Larry would seem to place more faith in data that might be 150-years old than data from a fellow boater who collected it last week. There are plenty of places that I enjoy boating where the official chart data is taken from a survey made more than 100 years ago.

Here is a good example: I have spent many weeks sailing the North Channel of Lake Huron using Canadian Chart 2286. The chart has the following legend:

The portion engraved lightly is taken from a survey by Lieut. H. W. Bayfield, R.N., 1822

OK, OK, that's the old part of the chart. The new part of the chart comes from a more recent survey:

Surveyed by Staff Commander J. G. Boulton, R.N., assisted by W. J. Stewart and D.C. Campbell, 1885

The soundings and positions shown on that chart date from either 190-years ago or the newer survey, only 127-years ago.

I think Larry might not have realized this because he doesn't own a copy of the official charts; he has a reprint in Richardson's Chart Booklet, and it probably doesn't include that information. But he has used Chart 2286 or a reprint in the North Channel. And a lot of the chart cartography translated to digital chart plotters came from those surveys.

You can toss in all the errors that might occur in the collection and organization of position and water depth data with a modern GPS and depth sounder, and I don't think you are going to be especially less accurate than Lt. Bayfield was in 1822.

To be complete, I should mention that just a few years ago most of really old sections of Chart 2286 were replaced by a newer chart, a small scale chart numbered in the 2207 series, and that data was taken in a newer survey, done in the 1990's. But the chart was not published until c.2001. The new soundings and position data only made it into the more recent reprints in the Richardson Chart Book, and only into the more recent digital cartography chart packages.

Another reason that chart data collected by individual boaters might become more useful in the future is the trend in our governments to have little or no interest in updating the official charts in areas that are not directly related to commercial shipping. In case you haven't noticed, you can get a lot more votes by giving out welfare cheese than you can by spending money on aids to navigation in recreational boating waters. If you think the future administrations of the government of the United States of America are going to be sending the Army Corps of Engineers to survey your favorite lake or some shallow backwaters of the coast or Great Lakes, you are probably living in dreamland. The best data for those areas will come from non-government sources.

jimh posted 11-11-2012 01:45 PM ET (US)     Profile for jimh  Send Email to jimh     
I have made some inquiries about the process of collecting and submitting water depth data for incorporation into the Navionics SonarChart program with regard to how certain variables will be handled. Here is what I have found.

With regard to the offset of the transducer from the water surface, Navionics appears to be assuming a default value of 1.5-feet, that is, it will assume that the SONAR transducer is typically mounted 1.5-feet below the waterline of the boat and that no offset value has been used in collecting the data. I don't quite have this nailed down, but I think that Navionics is assuming most people do not have an offset value entered, and when their SONAR tells them they are in 6-feet of water the actual depth is likely to be 7.5-feet. However, at the point of data entry into the system, I believe Navionics will offer users a chance to enter their own offset if they have one. Navionics also expects that they will get a lot of data sets from various individuals that will cover the same water, and they will compare one data set with all the others. In this way they plan to discover variances that are likely to be due to errors, and they can perhaps apply a correction factor to help correlate the variant data with previously submitted data. Or something like that.

In a similar way, Navionics will also provide input for the water level of the lake at the time of measurement so that the user data can be correlated to the standard level or chart datum for the particular body of water. If a user sends in data for soundings made when the water level was 2-feet above chart datum, this should correct for the difference.

I don't see too much worry about the position data. The typical modern GPS receiver with WAAS correction is going to be accurate to about 30-feet. These errors are probably random, so with enough data collected the error should begin to cancel out. In modern data analysis there are scientific methods available for averaging data values and determining the statistical significance from the range of error observed.

The user-collected will always be on a different presentation layer of a chart package, and if you really want to stick to an 1822 survey and the soundings some Royal Navy seaman made with a lead-line and wrote down on some parchment paper with a feather quill pen, you can turn off the user-collected data layer.

jimh posted 11-13-2012 10:20 AM ET (US)     Profile for jimh  Send Email to jimh     
Navionics has a short presentation that gives an overview of the SonarChart program. See

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