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/

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

"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

"otnmbrd" wrote in message
ink.net...
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

Got it...3AM blowing 35...12 foot seas...Check for the disturbed waves and
current swirls...yeah right. Watch the little birds...if they land it
probably is not deep.

Still at the old game otnmbrd? Would you really reverse course under those
conditions? Would you turn the boat across the wind?

Jim Donohue

Jim Donohue wrote:



Got it...3AM blowing 35...12 foot seas...Check for the disturbed waves and
current swirls...yeah right. Watch the little birds...if they land it
probably is not deep.

Still at the old game otnmbrd? Would you really reverse course under those
conditions? Would you turn the boat across the wind?

Jim Donohue

LOL I see you're still looking for the simple cure-all answer to navigation.
Sorry Jim, it doesn't exist.
You'll note I said use ALL means at your disposal. Sometimes those means
are limited due to conditions, be they visibility or sea conditions.
However, frequently there are any number of things you can look for
under many varied conditions which may help you determine that you are
"standing into danger" and your god, GPS will not tell you these things.
So, yes, I'm still up to the old games ..... if in doubt, stop, turn
around, sail across the wind, if those things are possible.
Don't keep going blindly based on a GPS fix ..../ use whatever other
tools may be available to you, be they natural, mechanical, or electronic.
Only a fool relies on one means of navigation and only a bigger fool
discards all the older methods which served and still serve, many of us
well, even if in a limited capacity.
G Maybe someday you'll learn to take your eyes off the GPS and see
what's going on around you.

otn

"otnmbrd" wrote in message
ink.net...
Jim Donohue wrote:



Got it...3AM blowing 35...12 foot seas...Check for the disturbed waves
and current swirls...yeah right. Watch the little birds...if they land
it probably is not deep.

Still at the old game otnmbrd? Would you really reverse course under
those conditions? Would you turn the boat across the wind?

Jim Donohue

LOL I see you're still looking for the simple cure-all answer to
navigation.
Sorry Jim, it doesn't exist.
You'll note I said use ALL means at your disposal. Sometimes those means
are limited due to conditions, be they visibility or sea conditions.
However, frequently there are any number of things you can look for under
many varied conditions which may help you determine that you are "standing
into danger" and your god, GPS will not tell you these things.
So, yes, I'm still up to the old games ..... if in doubt, stop, turn
around, sail across the wind, if those things are possible.
Don't keep going blindly based on a GPS fix ..../ use whatever other tools
may be available to you, be they natural, mechanical, or electronic.
Only a fool relies on one means of navigation and only a bigger fool
discards all the older methods which served and still serve, many of us
well, even if in a limited capacity.
G Maybe someday you'll learn to take your eyes off the GPS and see
what's going on around you.

otn

You are still full of BS otn. I make no suggestions not to use all
techniques...just that under many conditions all you got is the GPS.

Survival at sea is probabilistic. If the Gods are on your case no amount of
deciphering the currents and wave shapes will save you. You really think
you can detect a floating container when you can't see the bow?

In most circumstance it is probably 80 or 90% GPS/chart...10 or 20% to all
of the other things you can do. In heavy weather and deep water it is
pretty close to 100% GPS.

Under any circumstances the chart situation in some places is pretty sad.
For instance of the errors in the Pacific Coast of Mexico have been known
for many years...but we still await a fix. The purveyors deny responsibilty
shifting it to the charting agencies. The charting agencies show no desire
to fix the problems in our lifetime. Mostly Gov at its worst.

And to risk a broach because you feel uneasy? Because the waves don't look
right? Becasue you think you hear something? Sometimes I think you have
never been to sea...the number of people who hear or see things at night is
well known. Had a Captain on one occassion deploy his anchor in a 1000
fathoms because he could hear the freeway and knew we were about to go
aground. Sure he was extreme but virtually everyone has the problem to
some degree. It would take a very clear indicator before I risked my boat
against a GPS/Chart position.

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.

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.