http://www.goupstate.com/apps/pbcs.d...60/1051/NEWS01

Not that any of us will be cruising at 30 knots 500 feet below the surface
but navigating soly by GPS you are just as blind. Many of the charts we use
are from surveys over 100 years old.

--
Glenn Ashmore

I'm building a 45' cutter in strip/composite. Watch my progress (or lack
there of) at: http://www.rutuonline.com
Shameless Commercial Division: http://www.spade-anchor-us.com

On Sun, 16 Jan 2005 11:04:38 -0500, "Glenn Ashmore"
wrote:

http://www.goupstate.com/apps/pbcs.d...60/1051/NEWS01

Not that any of us will be cruising at 30 knots 500 feet below the surface
but navigating soly by GPS you are just as blind. Many of the charts we use
are from surveys over 100 years old.

Indeed. I was looking at some Softcharts of SW Carribean last night.
I loaded up some GPS tracks captured in the area and was unsurprised
to see a track pass through the middle of a sizable island.

It's an interesting situation. The government cartographic agencies
trust a century old report from a vessel that may not have gotten a
celestial fix in days, but not a solid GPS fix from a yachtsman.

I've often wondered whether it would be feasible to implement a public
or private program for vessels to have their instrument suites
validated and a way for them to upload the data to a central
authority.

With enough reports from a given area, said authority would then apply
statistical techniques to validate the data. For instance, my
cpRepeater program captures water depth, temp, and position (among
other things) and logs them. I could easily add something like an MD5
algorithm to digitally sign the log, proving that it has not been
altered. That would suffice for soundings. A snapshot of a radar
display would locate shorelines precisely.

The analysis would be tricky: apply celestial tide state, smooth the
results, look for outliers in the data, decide whether the resultant
confidence level in the data is sufficient for navigational use.
__________________________________________________ __________
Glen "Wiley" Wilson usenet1 SPAMNIX at world wide wiley dot com
To reply, lose the capitals and do the obvious.

Take a look at cpRepeater, my NMEA data integrator, repeater, and
logger at http://www.worldwidewiley.com/

"Glenn Ashmore" wrote in message
news:mgwGd.21097$EG1.17828@lakeread04...
http://www.goupstate.com/apps/pbcs.d...60/1051/NEWS01

Not that any of us will be cruising at 30 knots 500 feet below the surface
but navigating soly by GPS you are just as blind. Many of the charts we
use
are from surveys over 100 years old.

--
Glenn Ashmore

I'm building a 45' cutter in strip/composite. Watch my progress (or lack
there of) at: http://www.rutuonline.com
Shameless Commercial Division: http://www.spade-anchor-us.com



What do you recommend instead of GPS Glenn? Postulate a mountain top three
feet below the water surface. Not charted. I doubt that inertial or
celestial would offer any protection. Face it...every once in the while the
Gods **** on our pillar.

Jim Donohue

Yeah, the QEII (I think) ran aground about 20 years ago just off the
Elizabeth Islands on Cape Cod and in one of the most heavily traveled
areas of New England. The chart turned out to be wrong.

--

Roger Long



"Glenn Ashmore" wrote in message
news:mgwGd.21097$EG1.17828@lakeread04...
http://www.goupstate.com/apps/pbcs.d...60/1051/NEWS01

Not that any of us will be cruising at 30 knots 500 feet below the
surface
but navigating soly by GPS you are just as blind. Many of the
charts we use
are from surveys over 100 years old.

--
Glenn Ashmore

I'm building a 45' cutter in strip/composite. Watch my progress (or
lack
there of) at: http://www.rutuonline.com
Shameless Commercial Division: http://www.spade-anchor-us.com

It's not so much you should use your charts with a "grain of salt", as
you need be aware that they are not perfect and if you have any doubts,
you should use ALL means at your disposal, especially the "Mark I eyeball".
If you see discolored water, obvious current swirls, disturbed wave
action, (to name some) in a particular area, or your wake changes and
you bog down ..... these are indications that something may not be as
the chart suggest, and it doesn't matter whether you're using GPS,
celestial, radar, etc., for your navigation, you may want to stop or
reverse direction till you can figure things out or find a better route.

otn

I'd be happy with something simpler: allowing me to update my own maps.
IOW, I'd like to be able to import my own depth soundings into
electronic charts that I use. Does any such thing exist? I'm a big
Chesapeake gunkholer and a record of my soundings, synced with tides
would be very useful.

--
01/16/05 17:54

Yeah, the QEII (I think) ran aground about 20 years ago just off the
Elizabeth Islands on Cape Cod and in one of the most heavily traveled
areas of New England. The chart turned out to be wrong.

Is that the case? I heard about something similar but not a case of a
chart being wrong. A cruise liner enroute to Boston was under autopilot
but the gps lost lock for an extended period of time. During that period
the course was continued with the unit doing its own dead reckoning. By
the time it regained lock it was well off course and the new course to
the next waypoint took it over some rocks. None of the crew had noticed
the system had lost lock and all were trusting that the "gps referenced
autopilot" was safely steering the ship waypoint to waypoint. They also
did not bother to look and see that their course was now taking them
over the rocks.

That rings a bell and I think you might be right. The shoal being
shallower than charted may have been a secondary factor.

I don't think it would have been GPS in those days. Probably Loran.

--

Roger Long



wrote in message
.. .
Yeah, the QEII (I think) ran aground about 20 years ago just off
the
Elizabeth Islands on Cape Cod and in one of the most heavily
traveled
areas of New England. The chart turned out to be wrong.

Is that the case? I heard about something similar but not a case of
a
chart being wrong. A cruise liner enroute to Boston was under
autopilot
but the gps lost lock for an extended period of time. During that
period
the course was continued with the unit doing its own dead reckoning.
By
the time it regained lock it was well off course and the new course
to
the next waypoint took it over some rocks. None of the crew had
noticed
the system had lost lock and all were trusting that the "gps
referenced
autopilot" was safely steering the ship waypoint to waypoint. They
also
did not bother to look and see that their course was now taking them
over the rocks.

On Sun, 16 Jan 2005 17:02:09 -0600, wrote:

Yeah, the QEII (I think) ran aground about 20 years ago just off the
Elizabeth Islands on Cape Cod and in one of the most heavily traveled
areas of New England. The chart turned out to be wrong.

Is that the case? I heard about something similar but not a case of a
chart being wrong. A cruise liner enroute to Boston was under autopilot
but the gps lost lock for an extended period of time. During that period
the course was continued with the unit doing its own dead reckoning. By
the time it regained lock it was well off course and the new course to
the next waypoint took it over some rocks. None of the crew had noticed
the system had lost lock and all were trusting that the "gps referenced
autopilot" was safely steering the ship waypoint to waypoint. They also
did not bother to look and see that their course was now taking them
over the rocks.


Hmmm...can you spot the pattern?

A Cathay-Pacific jet out of London had an autopilot disengage after
a windshear alert while maneuvering in the terminal area last
October.
The crew saw the jet turning, but figured it was a response to the
wind-shear(??) The jet turned close by a mountain and continued
climbing, while the crew merrily concentrated on clean-up, though the
plane was near stall. When the controllers first queried the altitude
exceedence, the crew STILL thought they were responding appropriately
to a wind-shear (the w/s response CAN mandate holding attitude in a
climb, ignoring transient stall warnings).

When I sent this news report to associates, I heard back that
one of the people in that office had been on a flight with the cockpit
door open ( not a US long-haul, I'd think?) and heard the GPWS
calling "Pull up, Pull up" while the crew were argiung about
something....

Brian Whatcott Altus OK

wrote:
Yeah, the QEII (I think) ran aground about 20 years ago just off the
Elizabeth Islands on Cape Cod and in one of the most heavily traveled
areas of New England. The chart turned out to be wrong.


Is that the case? I heard about something similar but not a case of a
chart being wrong. A cruise liner enroute to Boston was under autopilot
but the gps lost lock for an extended period of time. During that period
the course was continued with the unit doing its own dead reckoning. By
the time it regained lock it was well off course and the new course to
the next waypoint took it over some rocks. None of the crew had noticed
the system had lost lock and all were trusting that the "gps referenced
autopilot" was safely steering the ship waypoint to waypoint. They also
did not bother to look and see that their course was now taking them
over the rocks.


I believe in the case of the QE2, the rock was charted but the depth was
wrong, plus they didn't allow for squat.
In the other case the antenna was disconnected to the GPS which forced
the system to go on DR, which coupled with other procedure errors ended
them on a sandbar.
Overall, the accuracy of existing charts is amazing considering the
equipment available for the original calculations, etc..
However, many need updating and upgrading for accuracy and and content
and this is going to be a slow process.

otn