On Tue, 18 Jan 2005 17:59:40 GMT, otnmbrd
wrote:

Jack Dale wrote:


My lack of faith in GPS was reinforced when the chartplotter showed
my boat on land while safely anchored stern-to in Princess Bay on
Wallace Island.

On the other hand, I did navigate through the rocks in Race Passage in
last year's Swiftsure using GPS. I had a paper chart in front of me
while I did it.

Jack



This is the problem/situation that many are noting, especially those
using chart plotters.
During most piloting exercises where we're underway, many minor
discrepancies between the chart plotter position and actual will not be
readily apparent as they are relatively small and due to the fact you
are normally giving a "safe berth" to most points you are passing, of
little consequence.
However, once you are anchored or moored or even working around a tight
docking situation, these discrepancies DO become readily apparent.
In most cases, I'm dealing with chart plotters on different vessels (all
gyro stabilized) that are using same/different/similar electronic
packages and unknown chart data (some charts I know to be older versions).
Depending on the vessel, I've noted errors of from @10' - 100' of a
variable nature (sometimes between trips, sometimes between vessels).
in this particular port. The most obvious being when alongside the dock.
Personally, when piloting, naturally my first choice is eyeball, but if
I have a GPS readout handy to where I'm standing I use it to confirm
speed and get a backup to my sense of set and drift, and where I have a
chart plotter to look at, I glance at it for a "birdseye" view, though I
put more weight on the "birdseye" view from the radar where accuracy is
concerned, as long as the particular radar picture is clear.
Naturally, what I'm discussing is for a particular port. Each port and
set-up will vary/differ .... my main point is that you should use
everything at hand, be aware of possible drawbacks to each and make
maximum use of the positives.

It would seem interesting to investigate what caused the errors in the
charting systems. My experience with non-charting WAAS receivers is
much tighter. At the slip we have used for the past few years, the GPS
not only tells us we are in our own slip, and not either adjacent, but
whether we are bow or stern in.

You did say the source for chart data was unknown.

I haven't purchased a charting system because I would still have to
keep paper charts even if I did. I am interested to read of your
experiences, and thank everyone for this thread.



Rodney Myrvaagnes NYC J36 Gjo/a


"Be careful. The toe you stepped on yesterday may be connected to the ass you have to kiss today." --Former mayor Ciancia

Rodney Myrvaagnes wrote:


It would seem interesting to investigate what caused the errors in the
charting systems. My experience with non-charting WAAS receivers is
much tighter. At the slip we have used for the past few years, the GPS
not only tells us we are in our own slip, and not either adjacent, but
whether we are bow or stern in.

You did say the source for chart data was unknown.

I haven't purchased a charting system because I would still have to
keep paper charts even if I did. I am interested to read of your
experiences, and thank everyone for this thread.



Rodney Myrvaagnes

I have a strong feeling that much the the information we all gather as
to possible anomalies in GPS fixes versus plotted positions/chart
plotter positions/actual positions will for the most part end up as very
case specific.
We will also need to know who's charts the plotter data is based on
(NOAA/British Admiralty) and is it up to date; who created the plotter
program; are all the components matched and compatible; is the error
consistent; etc. (much of this need some tech types to rule out or
confirm system problems versus charting problems).
Nowadays, all of what I'm seeing is very Port specific and not of much
help to the average boater, other than to say the possibilities exist.
I do note that I've seen a great improvement over the years that I've
been using chart plotters for this port, to the point that in some cases
I consider the units "right on", G with reservations.
Again, and as always on this subject ..... never rely exclusively on one
system, especially in confined waters.

otn

On Wed, 19 Jan 2005 17:24:31 GMT, otnmbrd
wrote:

Rodney Myrvaagnes wrote:


It would seem interesting to investigate what caused the errors in the
charting systems. My experience with non-charting WAAS receivers is
much tighter. At the slip we have used for the past few years, the GPS
not only tells us we are in our own slip, and not either adjacent, but
whether we are bow or stern in.

You did say the source for chart data was unknown.

I haven't purchased a charting system because I would still have to
keep paper charts even if I did. I am interested to read of your
experiences, and thank everyone for this thread.



Rodney Myrvaagnes

I have a strong feeling that much the the information we all gather as
to possible anomalies in GPS fixes versus plotted positions/chart
plotter positions/actual positions will for the most part end up as very
case specific.
We will also need to know who's charts the plotter data is based on
(NOAA/British Admiralty) and is it up to date; who created the plotter
program; are all the components matched and compatible; is the error
consistent; etc. (much of this need some tech types to rule out or
confirm system problems versus charting problems).
Nowadays, all of what I'm seeing is very Port specific and not of much
help to the average boater, other than to say the possibilities exist.
I do note that I've seen a great improvement over the years that I've
been using chart plotters for this port, to the point that in some cases
I consider the units "right on", G with reservations.
Again, and as always on this subject ..... never rely exclusively on one
system, especially in confined waters.

otn
In this connection I should say where I got these tight results. It is
a marina just south of the Holland Tunnel on the NJ side of the North
(Hudson) River. The chart survey is new, since it shows the floating
docks that were only built in 1989.

I use charts in Maine that use 18th and 19th Century surveys, and will
probably never get redone. The situation there is not the same as in
NY Harbor, where many charts are sold every year.

In Maine, I use the GPS the way I formerly used Loran C, for
repeatibility, in places I have already visited.



Rodney Myrvaagnes NYC J36 Gjo/a


"Be careful. The toe you stepped on yesterday may be connected to the ass you have to kiss today." --Former mayor Ciancia

It was a 39 foot Ericson by the name of Pneuma. Went aground coming out of
Minerva in November of 2003. Still has a web site. The details of the
grounding do not appear to have been made public. Conditions were close to
perfect.

I suspect Pneuma crew is not talking about what happened as the site is
silent on the subject. There is lots of discussion of the incident and the
rescue but little of the causals. Word at the time however was that they
were operating visually in almost perfect conditions.

Jim


"Jofra" wrote in message
...
Year before last we had a 38 foot sailboat enter Minerva reef by GPS.
After a couple of days decided to go out the other side via
visual...Guess what...Well they salvaged much of the equipment I
understand. Seems to me visual shortened their cruise and cost a lot of
money.

Jim Donohue

Jim

Thanks for comments Jim but not sure what point you are making. Are you
suggesting that if they had gone out of the Minerva Reef using GPS they
would still have their yacht? Possibly they would. I would like to know
more about the case. What were the conditions like, time of day, position
of the sun, cloud cover, sea conditions? Also when they went inside the
reef using GPS did they know the accuracy of the chart in relation to the
GPS?

cheers

jofra

Thanks for the info. Jim.

I can understand the crew not wanting to talk about what must have been a
devastating experience. However we all can learn from other people's
misfortunes.

Last year I attended a Power Point talk by the skipper who had lost his
yacht a month before. He explained what he had done leading up to the
grounding what he believed he had done correctly and the mis-calculations he
had made. He also answered questions. We all learned from the loss but it
must have taken considerable courage to talk to experienced yachties and
commercial fishermen on the loss.

You mentioned "Pneuma" and it is worth looking at web-site
http://www.latitude38.com/LectronicL...v21/Nov21.html

I quote in part:-

"Pneuma, Seattle-Based Ericson 39, Lost on South Minerva Reef
November 21 - Minerva Reef, South Pacific

Pneuma, the Ericson 39 from Seattle being cruised by Guy and Melissa
(no last name available) was lost Tuesday night while at anchor at South
Minerva Reef. The couple are safe. Minerva Reef is located about 250 miles
from Tonga on the way to New Zealand. It consists of two open ocean reefs,
which only fully break the surface at low tide."





Regards

Jofra








"Jim Donohue" wrote in message
news:lNEId.6837$ry.3578@fed1read05...
It was a 39 foot Ericson by the name of Pneuma. Went aground coming out
of Minerva in November of 2003. Still has a web site. The details of the
grounding do not appear to have been made public. Conditions were close
to perfect.

I suspect Pneuma crew is not talking about what happened as the site is
silent on the subject. There is lots of discussion of the incident and
the rescue but little of the causals. Word at the time however was that
they were operating visually in almost perfect conditions.

Jim


"Jofra" wrote in message
...
Year before last we had a 38 foot sailboat enter Minerva reef by GPS.
After a couple of days decided to go out the other side via
visual...Guess what...Well they salvaged much of the equipment I
understand. Seems to me visual shortened their cruise and cost a lot
of money.

Jim Donohue

Jim

Thanks for comments Jim but not sure what point you are making. Are you
suggesting that if they had gone out of the Minerva Reef using GPS they
would still have their yacht? Possibly they would. I would like to know
more about the case. What were the conditions like, time of day,
position of the sun, cloud cover, sea conditions? Also when they went
inside the reef using GPS did they know the accuracy of the chart in
relation to the GPS?

cheers

jofra

They had been at anchor but were moving. Or at least that was the story
from the rescuers. Never talked to Pneuma after the strike but there were a
number of conversation with the other boats at Minerva including those that
took part in the rescue..


I believe one of the boats was going to find out what happened but if they
relayed it I was not on the air at the time.

Jim

"Steven Shelikoff" wrote in message
...
On Sun, 23 Jan 2005 21:51:54 +1300, "Jofra" wrote:


Year before last we had a 38 foot sailboat enter Minerva reef by GPS.
After a couple of days decided to go out the other side via
visual...Guess what...Well they salvaged much of the equipment I
understand. Seems to me visual shortened their cruise and cost a lot
of money.

Jim Donohue


I quote in part:-

"Pneuma, Seattle-Based Ericson 39, Lost on South Minerva Reef
November 21 - Minerva Reef, South Pacific

Pneuma, the Ericson 39 from Seattle being cruised by Guy and Melissa
(no last name available) was lost Tuesday night while at anchor at South
Minerva Reef. The couple are safe. Minerva Reef is located about 250 miles
from Tonga on the way to New Zealand. It consists of two open ocean reefs,
which only fully break the surface at low tide."

Lost "while at anchor" at South Minerva Reef? That doesn't jibe with
Jim's story.

Steve

I'm surprised not to hear from you Jim.

Do you consider overcast conditions, late in the day and amongst dangerous
reefs "to be almost perfect conditions"?



jofra


Hello Jim

Steve made a valid point and there is another one. You (Jim) stated and I
quote:-
"Word at the time however was that they were operating visually in almost
perfect conditions"

This does not quite tie up with the only written evidence we have at the
moment:"-

" The weather was relatively benign, with overcast and 10-15 knots of
breeze. The wind was very shifty, however, due to the effects of a
stationary front. Three boats remained at North Minerva, which is about 20
miles up from South Minerva.
"At about 2000 local time, we heard Pneuma's Mayday. We had been tuning up
Russell Radio for the evening roll call, but just happened to pause long
enough on the Puddle Jump frequency to hear Guy calling for help. We were
not the first to hear the Mayday, as it was heard over VHF on another
boat."

Presumably the problem occurred close to the time of the mayday being
heard which was 2000hrs local time or 1900hr NZDT. I haven't checked the
time of twilight on 21 November but I would at least expect darkness to
be galloping towards the horizon at the very least. Certainly not "almost
perfect conditions" that you stated.
Further the we know the weather was overcast with 10 - 15 knots of breeze.
No-one with reef experience would state that overcast conditions were
"almost perfect conditions".

Cheers

Jofra

Actually I was trying to dig through the archives to see if I could find any
more pertinent information. PacSeaNet keeps the last two years so I should
be able to find something from the area at the time in question. I actually
have tracks of some of the boats but I have not been able to get at the more
than a year old stuff yet. I have some close area data for the date that
says it was overcast. But nothing actually at or real close to Minerva. I
have nothing that refines the time of the actual incident. Given the small
number of boats in VHF range it could have occurred any time during the day
or even the day before. I am still trying to determine whether he
whacked the reef going out or lost his anchor. At the time it appeared it
was a moving thing...but the report in Latitude 38 contradicts that.

Note that I don't mind it being overcast and visually difficult. That
merely supports my positon that he should have run out on GPS waypoints.

However I think it best in these things that we get as close to what
actually occurred as possible.

Jim


"Jofra" wrote in message
...
I'm surprised not to hear from you Jim.

Do you consider overcast conditions, late in the day and amongst dangerous
reefs "to be almost perfect conditions"?



jofra


Hello Jim

Steve made a valid point and there is another one. You (Jim) stated and I
quote:-
"Word at the time however was that they were operating visually in almost
perfect conditions"

This does not quite tie up with the only written evidence we have at the
moment:"-

" The weather was relatively benign, with overcast and 10-15 knots of
breeze. The wind was very shifty, however, due to the effects of a
stationary front. Three boats remained at North Minerva, which is about
20 miles up from South Minerva.
"At about 2000 local time, we heard Pneuma's Mayday. We had been tuning
up Russell Radio for the evening roll call, but just happened to pause
long enough on the Puddle Jump frequency to hear Guy calling for help. We
were not the first to hear the Mayday, as it was heard over VHF on
another boat."

Presumably the problem occurred close to the time of the mayday being
heard which was 2000hrs local time or 1900hr NZDT. I haven't checked the
time of twilight on 21 November but I would at least expect darkness to
be galloping towards the horizon at the very least. Certainly not "almost
perfect conditions" that you stated.
Further the we know the weather was overcast with 10 - 15 knots of
breeze. No-one with reef experience would state that overcast conditions
were "almost perfect conditions".

Cheers

Jofra