Submitted for your approval:

Here are two pics taken from Coastal Explorer using raster and vector
charts of Vineyard Haven. The photo is superimposed, merged in about
50%.

http://www.sv-loki.com/VHVectorPhoto.jpg
http://www.sv-loki.com/VHRasterPhoto.jpg

Note that in the Vector version, many of the features are mis-aligned.
In particular, the breakwater falls short about 100 feet, which
could cause an embarrassing situation in the fog.

These charts were what "came" with the system, there was no special
effort to setup certain charts - I simply zoomed on on one of my
favorite spots and selected vector and then raster charts only.

The raster chart is 1:10,000 "HARBOR" type, 4/1/06
The vector chart is also listed as "HARBOR" but is only 1:40,000.
If you click on the correct info panel, it shows the following in red:

"WARNING! The data in this area is incomplete. Dangers to
navigation exist in this area and are not included. The mariner
is advised to use the corresponding largest scale raster or paper
chart to navigate in this area."

So I looked around for another chart of the area and found one that
was also 1:40,000 but included more detail:

http://www.sv-loki.com/VHVector2Photo.jpg

This did not have the same "short breakwater" problem but its hard to
say it was more accurate.

As much as I like reviewing vector charts in the comfort of my home,
or down below, I still happy to use paper as my primary reference in
the cockpit.

Thats precisely the argument.
If your chart is accurate to only 60 ft., if you apply a magnification
of 10X, the accuracy is STILL 60 ft. and not the (apparent) visual 6ft.
that would be the 'new resolution' at an increase of magnification @
10X.


In article , Wayne.B
wrote:

On Thu, 14 Dec 2006 20:53:15 GMT, Rich Hampel
wrote:

ou can do so with graphical magnification .... but the answer is
nearly ALWAYS wrong.

Wrong is relative, and it depends on the chart. Most of my vector
charts for US waters with stable shorelines are accurate to within 50
or 60 feet. If you are 50 feet away from your charted position, is
that wrong? It depends. 99% of the time 50 feet is good enough to
bring you into line with a Mark I eyeball fix, and that's good enough
for me. For those areas with unstable inlets, shorelines and/or 1800s
survey data, the type of chart makes very little difference. They are
no better than a general guideline to get you started.

On Thu, 14 Dec 2006 13:22:14 +0000, Roger Long wrote:

A friend and professional mariner passed this on to me. Maybe it's old news
here, I haven't been following the issue. But, just in case anyone hasn't
heard:

MapTech's agreement with NOAA for raster charts has expired and NOAA has now
made its raster charts available for free online.

This means that you can get entire raster chart collections for free from
NOAA. There 1,016 BSB format charts online at NOAA's website, but the
maximum that can be downloaded at one time is 100. So if you're intent on
suddenly accumulating a complete chart library of the U.S., it may take you
some time and effort. But if you're only looking for a few specific areas,
or for updating your existing library, this is the easy way to do it. The
gov't continues to update these charts electronically as necessary.

Several private firms -- MapTech, Nobeltec, Richardson's, etc. -- are
repackaging these raster charts for sale on CDs and DVDs. Sometimes you can
get such a disk free as a sales premium, if you buy another navigational
product from the same vendor.

For more information and downloads:
http://nauticalcharts.noaa.gov/mcd/Raster/Index.htm

Awesome! I'm glad those Maptech *******s have lost their monopoly!

The gov't is also making vector charts available for free on-line
down-load, but the available number is less, and the vector charts are
for some reason more difficult to download. The vector charts are also
more difficult to use, but that's a personal opinion. To me, vector
charts just don't look real; on my computer console a vector chart
reminds me of a video game.

Eventually the makers of plotter software will figure out better ways to
display these charts.

Matt O.

On Thu, 14 Dec 2006 13:22:14 +0000, Roger Long wrote:

A friend and professional mariner passed this on to me. Maybe it's old news
here, I haven't been following the issue. But, just in case anyone hasn't
heard:

MapTech's agreement with NOAA for raster charts has expired and NOAA has now
made its raster charts available for free online.

Apparently Maptech still owns the BSB file format. I'm not sure how this
affects things in a practical sense, such as the gov't still having to pay
license fees, or other software developers being able to compete freely.

This means that you can get entire raster chart collections for free
from NOAA. There 1,016 BSB format charts online at NOAA's website, but
the maximum that can be downloaded at one time is 100. So if you're
intent on suddenly accumulating a complete chart library of the U.S., it
may take you some time and effort. But if you're only looking for a few
specific areas, or for updating your existing library, this is the easy
way to do it.

Easy, my ass! This website is a disaster. Offhand I can think of several
ways they could have done this much easier, making charts a lot easier and
faster to find and download, with a lot less load on their servers. NOAA
needs better web developers.

I do appreciate their making this available though!

Matt O.