Raster charts now free
 

Here's what I think the OP is getting at:

http://home.maine.rr.com/rlma/Vector.jpg

CAD, which I also use a lot is vector based so lines are mathematically
thin. They don't get thicker as you zoom in. The view on the left, drawn
with CAD, is true scale so the boat is a comfortable distance from the
sounding line.

In the view on the right, the line is zoomed 1000 times. If the system
generated icon showing your boat doesn't scale at the same time as the view,
you get an image which makes it look like you are still a comfortable
distance off. But, it this view, the distance to the sounding line is only
a few inches. Throw in normal chart inaccuracy and, THUNK!

--
Roger Long

Raster charts now free
 

Wayne.B wrote:

In Maine, except for the Portland Harbor channels, I use charts just as much
in waters I'm familiar with as in new areas. It's pretty much mandatory in
our complex geography.

If I had a powerboat or a larger sailboat with a pilothouse, dedicated nav
station, and crew to do a lot of the other tasks, I would certainly have a
full electronic set up with electronic charts, chart plotters, etc. Setting
up and using something like that was a primary reason for thinking about
getting a powerboat when we first decided to get back into boating. On the
sailboat however, it's a different dynamic, a different mindset, keeping it
simple is part of the charm.

I actually find that I prefer the chartbooks more in unfamiliar areas.
Maybe it's just being old enough to have run fog clock and compass back in
the days when only a few boats had Loran and they had cathode ray displays
where you had to turn knobs to match pulse rates. Budgets and the physical
realities of small sailboat life dictate a small GPS. I use the chartbook
for overall situational awareness and the GPS for the close in view and
position. It's a nice compromise that doesn't make me feel I'm getting too
far from my roots.

If I were cruising in a boat like yours, I'm sure I would have and greatly
enjoy using pretty much the same set up you have.

You ought to open up those chart books though. It's a lot more enjoyable
anticipating and planning the next day's cruising with those nice paper
graphics in your hand than looking at a LCD display.

--
Roger Long

Raster charts now free
 

Oops. Wayne B. didn't write that, I did. That little header slipped up out
of the window when I erased the quote.

--
Roger Long

Raster charts now free
 

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.

Raster charts now free
 

Being in the business of drawing stuff, it makes sense to me.

Raster charts are machine images of the "gold standard" the NOAA paper
charts. Conversion to vector is a massive process that requires tracing
every feature. It's too large a job for incorporating human judgement on
every detail but requires too much human judgement and pattern recognition
for a machine to be entrusted with the whole task. The result is an
overwhelming number of places for errors to creep in.

I've tried several methods of converting raster scans of my old hand drawn
plans into vector CAD. It takes almost as long to clean them up as to have
just traced them from scratch. Until NOAA starts drawing the charts in
vector form from the get go, I don't see any way that vector charts are
going to be as reliable in any probable economic scenario.


Jeff wrote:
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.

--
Roger Long

Raster charts now free
 

On Fri, 15 Dec 2006 13:32:51 GMT, "Roger Long"
wrote:

You ought to open up those chart books though. It's a lot more enjoyable
anticipating and planning the next day's cruising with those nice paper
graphics in your hand than looking at a LCD display.

Actually I've gotten very used to doing my "next day" plan on the PC
using raster charts. They look exactly like the paper charts, and the
utility/convenience of electronic course plotting is not to be
believed unless you've tried it. Plotting across chart boundries is a
non-issue and you end up with a complete list of waypoints, courses
and distances which can be saved for backup purposes. Everything gets
copied to a backup PC at the lower helm, and the previous night's work
gets taken up to the flybridge. Underway the PC, a "Toughbook", sits
side by side with the Furuno course plotter and provides different but
redundant information.

Like you say, the problem with sailboats is where to put all the
"stuff". Down below at the nav station is not too handy unless you've
got a full time navigator in the crew, and the space top side is never
enough even with a wheel pedestel.

Raster charts now free
 

Comments to several msg's in this thread without attribution:
1. The greatest advantage to paper charts over either vector or raster is
the zoom & pan speed.
2. Not disputing the definition of a vector, which indeed has no thickness.
But, every cad system that I've used, and there are quite a few, are capable
of drawing lines with thickness and the thickness does scale.
3. The NOAA ENC charts do seem to have thickness for their lines.
4. Fugawi limits the zoom scale on vector charts to 1000, whatever that
number means with respect to vectors. So, I can't fully test my line
thickness hypotheses.
5. Not 100% sure, more like 10%, but I'm of the impression that NOAA is
creating / recreating / updating the ENC charts from satellite surveys.
BF

"Roger Long" wrote in message
...
Being in the business of drawing stuff, it makes sense to me.

Raster charts are machine images of the "gold standard" the NOAA paper
charts. Conversion to vector is a massive process that requires tracing
every feature. It's too large a job for incorporating human judgement on
every detail but requires too much human judgement and pattern recognition
for a machine to be entrusted with the whole task. The result is an
overwhelming number of places for errors to creep in.

I've tried several methods of converting raster scans of my old hand drawn
plans into vector CAD. It takes almost as long to clean them up as to
have
just traced them from scratch. Until NOAA starts drawing the charts in
vector form from the get go, I don't see any way that vector charts are
going to be as reliable in any probable economic scenario.


Jeff wrote:
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.

--
Roger Long

Raster charts now free
 

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.

Raster charts now free
 

BF wrote:

2. Not disputing the definition of a vector, which indeed has no
thickness. But, every cad system that I've used, and there are quite
a few, are capable of drawing lines with thickness and the thickness
does scale.

Certainly, you can always draw or convert to a polyline and assign thickness
but this wasn't meant to be a discussion about CAD.
If vector chart systems use something similar, which would increase the data
storage file sizes significantly, then the OP must be talking about
something different than what I demonstrated.

--
Roger Long

Raster charts now free
 

On Thu, 14 Dec 2006 21:19:35 -0500, Wayne.B wrote:

On Thu, 14 Dec 2006 18:58:45 GMT, "Roger Long"
wrote:

Actually, you're agreeing with my friend. I'm still using paper myself
although with the GPS as an adjunct.

Olde school, very olde.

If you sail in one general area that you come to know, love and have all
of the paper charts for, it's not so bad. I sailed like that on Long
Island Sound and points east for many years.

These days however when we are cruising thousands of miles per year, to
many different areas, the idea of navigating only it with paper charts
would be daunting indeed. I carry chart books for backup but most of
them never get opened.

After awhile, storage for all those paper charts becomes an issue!

All those charts can be expensive too.

I'm partly old-school too -- I usually have a paper chart in front of me
as well as an electronic one running on a laptop.

If I were cruising long distance, I'd be relying on electronic charts
rather than buying paper ones all the time. Some may worry about
relying on electronic equipment. But if an F16 needs reliable software to
stay in the air, then surely we can figure out a reliable system for our
silly little boats.

Matt O.