Are those up to date charts really up to date?

[brownr377]

Recent thread I was looking at started me thinking on this. I took this excerpt (attached) from NOAA chart 18427, this is a little bit of water that concerns the thread that started me thinking it covers some tricky passes and mud flats from Skagit Bay to up to Padilla Bay including Deception Pass. I downloaded this today it's totally up to date, but the survey data is, well, parts of it are a bit stale you might say.

How do you folks out there deal with this kind of issue on ENC charts? I don't see a way of pulling this kind of info out of them, it's why I prefer to use RNC charts, and look over paper charts, admittedly I'm a bit of a luddite.

It's like streaming music for me, I like to do that cause it's so convenient I miss all the context though. The liner notes gave so much info, like who performed on tracks, producers, songwriters, notes on making the album, hell a lot of my old-time CD's give banjo and fiddle tunings, it's context that gets stripped off of the digital medium. Same thing seems to happen with anything that gets digitized be it maps, music, or nautical charts.

So how do ya'll deal with getting the big picture on ENC charts? I'm really interested in perspectives this thing.

[Paul L]

There's really nothing wrong with those old surveys as long as they have had their datum corrected. You aren't in an area where a lot changes quickly and the cartographers who surveyed the PNW in the late 1800s were amazing.

With vector charts it is often difficult to impossible to see the survey information on a lot of chartplotters. Each new area we go into we assume significant chart error. Then we start verifying by depth and by radar. After we get some experience we learn to trust, or rarely distrust, our charts for that area.

[Adelie]

There are places in the pacific where the charts are based on info from the 1700s.

This is why you use all means of navigation and don’t rely on one source.
Start with you eyes by keeping watch and then use the depthsounder.

As far as the Skagit chart goes, a lot of the areas with old surveys are pretty deep or are mudflats.
The places with traffic that are also subject to change are updated occasionally.

[valhalla360]

Not only are there charts from the 1700-1800's but in areas with shifting bars, a survey from a month ago may be wrong if a storm rolled thru.

Use the best chart available but watch the bouys and locals and if unsure send out a call to see if locals have some advice or will let you follow them in...lots of options instead of assuming the chart is right.

[brownr377]

All good points, well taken. Yes there's not a whole lot of commercial traffic travelling on Saratoga passage, I can get that resurveying a nonnavigable mud flat is not a useful exercise for anyone.

About correcting the datum, do I have it right, so long as the survey data has been corrected or updated, don't know the right term, to WGS1984 things will line up with GPS coordinates? Assuming an accurate survey?

And I am astonished at how good the surveying was in the Sound those folks were something. As a total thread drift, I've been looking for any readable books on Captain Vancouver's expedition but can only find one book with pretty bad amazon reviews, does anybody know of a good source?

[deblen]

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[CaptTom]

Well, that particular chart, 18427, has had 67 changes since its last printing in May of 2013. That's actually one of the fewest changes I've seen in a while.

Some highlights: Lots of adding, deleting, changing and re-configuring of markers, buoys and even a lighthouse. Fish pens being established and moved. A note about a strong current under certain tide conditions. New private aids for a marina. A change to the controlling depth in a channel.

I didn't see any "rock reported," those are the ones that get my attention in our area.

Hey, if these things aren't important to you, then get your charts used, off eBay.