Why are commercial charts often so much better detailed than government charts?

[foojin]

It was always my understanding that commercial nautical chart makers licensed the chart data collected by government agencies and produced charts that were interpretations of that data.

However, recently I have used commercial charts in BC and Washington state that are much more detailed than NOAA or CHS charts. In the Broughtons where we are now, there is no comparison. I’m talking vector charts. I haven’t really compared raster charts.

Are government agencies selling enhanced data to commercial vendors that they are not including on the charts they produce, are vendors enhancing their charts in another way or am I out to lunch about where vendors get chart data?

[Dsanduril]

Some commercial charts use additional data sources. Take this from Navionics, for instance:

Continuously expanded with data from numerous highly qualified public and private sources, including our own surveys, Notices to Mariners and data reported by users.

Of course, the devil is in the details, knowing the quality of the private data is a bit more difficult.

[Herreshoff]

Apparently some years ago sailors were given depth sounding units and were asked
To gather data for the big companies.

I’m currently looking for ‘non Navonics’ charts of Australia to apply to some software. The government here doesn’t supply any like the noaa charts in North America.

[seandepagnier]

Originally Posted by foojin

However, recently I have used commercial charts in BC and Washington state that are much more detailed than NOAA or CHS charts. In the Broughtons where we are now, there is no comparison. I’m talking vector charts. I haven’t really compared raster charts.

Which exact charts are you using?

This data might be really nice and accurate 99% of the time, and the rest have incorrect information. It's difficult to verify user sourced data.

[Albro359]

Interesting question....how does it work?
We are in the Yasawa islands in Fiji and there is only one "official" chart Fijian F5 which is not very deatiled There are some hand detailed charts from the '70s by Picmere sold as a set F105, but they have no soundings at all, and that's it.....
We have Navionics in a B&G plotter and C-Map in our Furuno NavNet VX2 system, all up to date and they are quite different.
Navionics in particular in some places has great detail, including soundings, that has never been on official charts but in other places has no detail at all, indicates reefs where there aren't any and worse, doesn't show a lot of the reefs at all, and often the wrong shape and position.
C-map seems to be based on the "officlal" charts but also has detail that's not on the paper versions...in some places.
Overall the C-map charts seem to me to be more reliable here.
I have come across "iPad" cruisers here who only have Navionics on their iPads and nothing else, no paper charts, nothing ...that's dangerous here !

We also have MaxSea TZ on a laptop with both Navionics and C-Map charts, and they are different again !
We also have OpenCPN with GE2KAP satellite pictures for almost everywhere we go...as a reality check.

The variations in all of these products means that you can't trust any of them absolutely and it pays to have as many sources as possible, AND make maximum use of the Mk1 Eyeball !

[bstreep]

My Uncle was a US Navy oceanographer, and captained one of the survey vessels. It's really this simple: The Navy is really only interested in where their ships can go. If the water is too shallow for ships, how shallow it is, doesn't really matter.



With that understanding, most of the rest of the chart areas are from surveys by sailing ships. So, they are old and inaccurate.