| Page 1 of 2 | 1 | 2 |
|
|
Use your charts with a grain of salt.
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. |
|
|
"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 |
On Sun, 16 Jan 2005 19:31:22 GMT, "Roger Long"
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. -- Much more recent than that. I kept a copy of the last chart edition before the grounding just to show people. It was surveyed quite promptly after the grounding. THe new edition looks very different. BTW, the previous survey was not 100 years old. It was 1939. WW2 intervened or I expect the job would have been completed. Rodney Myrvaagnes NYC J36 Gjo/a Capsizing under chute, and having the chute rise and fill without tangling, all while Mark and Sally are still behind you |
|
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 |
On Sun, 16 Jan 2005 23:17:11 GMT, "Roger Long"
wrote: 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. Can't tell what you are talking about. Both the QE2 and Nantucket shoals incident are quite recent. The QE2 was a chart problem, since corrected, and had nothing to do with autopilot or any other automated gear. The Nantucket shoals incident was from a system that ran on DR for 600+ miles with the GPS disconnected. Rodney Myrvaagnes NYC J36 Gjo/a Capsizing under chute, and having the chute rise and fill without tangling, all while Mark and Sally are still behind you |
I think that incident occurred several years ago. The QE2 did suffer from a mysterious power
ailment and found itself adrift for several hours in the 1980's while cruising thru an area known as the Bermuda Triangle... but I will leave it at that. The QE2 grounding was also found to be exacerbated by a previously unknown condition the ship had while at speed, it was found to "squat" down 6 feet. "Roger Long" 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. |
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. If I might use an analogy. How many out there are prepared to drive their car using GPS only? Jack __________________________________________________ Jack Dale Swiftsure Sailing Academy Director/ISPA and CYA Instructor http://www.swiftsuresailing.com __________________________________________________ |
What I recall reading about the QE2 hitting the rock there (divers confirmed
that there was recent bottom paint scuffed on the rock, and I don't think there was an indication that the rock had less water than the chart showed) is that she was running at too much speed for that little clearance between hull and sea floor. The hydrodynamic forces from speed in shallow water will pull the stern down. I see this happen frequently, and when it does, besides thinking about QE2, I know I'd better head to deeper water, or slow down. I just couldn't believe the captain didn't think about this when he was steaming along near the rock. "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. -- Roger Long "Glenn Ashmore" wrote in message news:mgwGd.21097$EG1.17828@lakeread04... http://www.goupstate.com/apps/pbcs.d...NYT02/50115036 0/1051/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 |
The Nantucket shoals incident was from a system that ran on DR for
600+ miles with the GPS disconnected. THAT is the story I was remembering. None of the crew noticed. No one was running their own plot. |
When did these incidents happen? I lived on the Cape in the late 70's
so I may be transferring the memory back to that association. When did they start installing GPS on big ships? -- Roger Long "Rodney Myrvaagnes" wrote in message ... On Sun, 16 Jan 2005 23:17:11 GMT, "Roger Long" wrote: 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. Can't tell what you are talking about. Both the QE2 and Nantucket shoals incident are quite recent. The QE2 was a chart problem, since corrected, and had nothing to do with autopilot or any other automated gear. The Nantucket shoals incident was from a system that ran on DR for 600+ miles with the GPS disconnected. Rodney Myrvaagnes NYC J36 Gjo/a Capsizing under chute, and having the chute rise and fill without tangling, all while Mark and Sally are still behind you |
This is a well know effect and you can even see it in something as
easy moving as a kayak. Find a tapered sandbar and a spot where there is two to three inches of clearance over the bottom. Then paddle fast over it. You will stick hard, stop, and then float off. The waves that roll in and break will show you how much water even a kayak moves. It's a very interesting demonstration of hydrodynamics. -- Roger Long "Garland Gray II" wrote in message news:K%HGd.77623$Jk5.65403@lakeread01... What I recall reading about the QE2 hitting the rock there (divers confirmed that there was recent bottom paint scuffed on the rock, and I don't think there was an indication that the rock had less water than the chart showed) is that she was running at too much speed for that little clearance between hull and sea floor. The hydrodynamic forces from speed in shallow water will pull the stern down. I see this happen frequently, and when it does, besides thinking about QE2, I know I'd better head to deeper water, or slow down. I just couldn't believe the captain didn't think about this when he was steaming along near the rock. "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. -- Roger Long "Glenn Ashmore" wrote in message news:mgwGd.21097$EG1.17828@lakeread04... http://www.goupstate.com/apps/pbcs.d...NYT02/50115036 0/1051/NEWS01 Not that any of us will be cruising at 30 knots 500 feet below the surface but navigating soly by GPS you are just as blind. Many of the charts we use are from surveys over 100 years old. -- Glenn Ashmore I'm building a 45' cutter in strip/composite. Watch my progress (or lack there of) at: http://www.rutuonline.com Shameless Commercial Division: http://www.spade-anchor-us.com |
|
|
When cruising in The Bahamas, our chartplotter showed us
sailing over land on a fairly regular basis. Doug s/v Callista "Glenn Ashmore" wrote in message news:mgwGd.21097$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 |
Roger Long wrote:
When did these incidents happen? I lived on the Cape in the late 70's so I may be transferring the memory back to that association. When did they start installing GPS on big ships? As systems developed they were installed on ships. "Sat Nav" in the 70's, "GPS" in the 80's. Nowadays you are seeing a greater usage of integrated systems (GPS, radar, chart plotter, AIS, Doppler). The biggest problem (aside from the mistaken total reliance) is that the chart display and GPS don't always match exactly. BTW, squat has been known about for many, many years .... it just hasn't been given as much attention as it needed by those in "open water" conditions. Since the QE2 incident you see far more ships with "squat tables". 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 |
On Mon, 17 Jan 2005 10:59:01 GMT, "Roger Long"
wrote: When did these incidents happen? I lived on the Cape in the late 70's so I may be transferring the memory back to that association. When did they start installing GPS on big ships? Much more recent. The NTSB hearings report from the Nantucket Shoals grounding just appeared in Professional Mariner last fall. The QE2 grounding was in the early 90s, and the course was agreed on by the skipper and the pilot. If the chart had been correct, squat would not have made the ship hit anything. With the actual reef that was(is) there, the ship would have hit no matter how slowly it was moving. It was an incomplete survey, pure and simple. 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 |
On Mon, 17 Jan 2005 18:06:21 -0500, Rodney Myrvaagnes
wrote: It was an incomplete survey, pure and simple. ==================================== And it happened right down the road, so to speak, from the Woods Hole Oceanographic Institute. Fortunately I've never ownned a boat that draws as much as the QE2, otherwise I would have surely left my mark in many more places. |
Jim Donohue wrote:
You are still full of BS otn. LOL Of course I am, I'm a career seaman. The difference between us is, I know when I'm BSing, but you have neither the experience or knowledge to know when I am, else you'd know I never BS about navigation safety. I make no suggestions not to use all techniques...just that under many conditions all you got is the GPS. ...... and as just as many conditions, all you got is the "old" methods..... i.e., it's a rare case when you can't make helpful use of the natural conditions occurring around you, if you know what they are and how to use them. Survival at sea is probabilistic. If the Gods are on your case no amount of deciphering the currents and wave shapes will save you. Not always true .... often true, but not always. You really think you can detect a floating container when you can't see the bow? You want to explain what that has to do with navigation? The discussion is navigation, not collision/allision avoidance. 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. Depending on the vessel and navigational equipment available, there's a good chance that if you were in charge of a watch, for me, you would change your ways real quick or find a new berth at the first port. 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. G I can't disagree with any of this. However, from involvement in creating a new chart, I do know that many cartographers are trying with limited resources to correct and upgrade our charts, with results that could indeed be better, but their failure has more to do with idiot politicians, than dipsquat beauracrats. 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. LOL I think I said this once before ..... you must be a lawyer. Go back and read what I said again. I said "if it's possible". You do what is right for the conditions and vessel you are on .... and this MAY involve risking a broach. YES, if the waves don't look right, you weigh your options and proceed. YES, if you think you hear something you shouldn't, you weigh your options and proceed ("proceed" may mean "stop"). One thing I've learned from reading your post.... you may know celestial, you may know radar, you may have some deep sea time, etc.. BUT, the only thing you MAY be any GOOD at, is reading a GPS, and I'm not too sure of that. BG As to having been to sea ..... EG "I've wrung more salt water out of my socks than you've ever floated on", to quote an old Bosn I knew. otn |
"otnmbrd" wrote in message ink.net... Jim Donohue wrote: You are still full of BS otn. LOL Of course I am, I'm a career seaman. The difference between us is, I know when I'm BSing, but you have neither the experience or knowledge to know when I am, else you'd know I never BS about navigation safety. I make no suggestions not to use all techniques...just that under many conditions all you got is the GPS. ..... and as just as many conditions, all you got is the "old" methods..... i.e., it's a rare case when you can't make helpful use of the natural conditions occurring around you, if you know what they are and how to use them. Survival at sea is probabilistic. If the Gods are on your case no amount of deciphering the currents and wave shapes will save you. Not always true .... often true, but not always. You really think you can detect a floating container when you can't see the bow? You want to explain what that has to do with navigation? The discussion is navigation, not collision/allision avoidance. 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. Depending on the vessel and navigational equipment available, there's a good chance that if you were in charge of a watch, for me, you would change your ways real quick or find a new berth at the first port. 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. G I can't disagree with any of this. However, from involvement in creating a new chart, I do know that many cartographers are trying with limited resources to correct and upgrade our charts, with results that could indeed be better, but their failure has more to do with idiot politicians, than dipsquat beauracrats. 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. LOL I think I said this once before ..... you must be a lawyer. Go back and read what I said again. I said "if it's possible". You do what is right for the conditions and vessel you are on .... and this MAY involve risking a broach. YES, if the waves don't look right, you weigh your options and proceed. YES, if you think you hear something you shouldn't, you weigh your options and proceed ("proceed" may mean "stop"). One thing I've learned from reading your post.... you may know celestial, you may know radar, you may have some deep sea time, etc.. BUT, the only thing you MAY be any GOOD at, is reading a GPS, and I'm not too sure of that. BG As to having been to sea ..... EG "I've wrung more salt water out of my socks than you've ever floated on", to quote an old Bosn I knew. otn Actually I am by training and a long career an engineer. It is what seperates us OTN...you react I go for understanding. Sure your socks are soaked in salt...so perhaps is your brain. I think with your long time frame at mis-understanding this stuff you are very well qualifled for say Chief Officer on the Royal Majesty. He did a truly fine job of successfully identifying the unidentifyable...as I am sure you would. But he was really salty. Wish you could have been on our little trip with the "freeway" Captain...you could have helped him set the anchor. I prefer to navigate around floating objects as well as fixed ones. If you ignore the floaters I assure you something you would rather avoid is likely to occur. Jim |
On Sun, 16 Jan 2005 23:34:23 -0500, Rodney Myrvaagnes
wrote: On Sun, 16 Jan 2005 23:17:11 GMT, "Roger Long" wrote: 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. Can't tell what you are talking about. Both the QE2 and Nantucket shoals incident are quite recent. The QE2 was a chart problem, since corrected, and had nothing to do with autopilot or any other automated gear. I heard they had more of a squat problem. As in they forgot to figure in the ship's squat at their speed over the shoal. Mark E. Williams snip |
Jim Donohue wrote:
Actually I am by training and a long career an engineer. It is what seperates us OTN...you react I go for understanding. No. I reason, while you go for understanding based solely on science and engineering. Your problem is you don't understand how to use or make use of the science and engineering you know, within the real world that exist around us. Sure your socks are soaked in salt...so perhaps is your brain. I think with your long time frame at mis-understanding this stuff you are very well qualifled for say Chief Officer on the Royal Majesty. He did a truly fine job of successfully identifying the unidentifyable...as I am sure you would. But he was really salty. LOL I don't mis-understand this "stuff". If I had been Master or Chief Officer on that ship, I would have realized early that "WE" had a problem. "Salty" is not saying you have such and such a license or you have made such and such trips. Salty is saying you've always made them safely, taking into consideration the various conditions and noting the possible errors in your systems and actions. Wish you could have been on our little trip with the "freeway" Captain...you could have helped him set the anchor. LOL would have probably sat back and had a good laugh, as long as his actions didn't endanger anyones safety. I prefer to navigate around floating objects as well as fixed ones. If you ignore the floaters I assure you something you would rather avoid is likely to occur. Jim I try to ignore nothing ( not always successful), but I also try to learn something new, every time I'm on the water, no matter how insignificant, and unlike you, I'm still learning, not hung up on the god, GPS. The recent rains in S. Ca. have shown all of us, not only ways to see currents, but the need to see the possibilities of way we can avoid many of those dangerous floating hazards. otn |
Enjoying your little tiffs you guys. Obviously you both have a certain
amount of sense as you are both still around or else the gods have been particularly kind.... Just come back from Fiji where we stayed for several months. Many of the charts predate GPS's and the result is that they may be out by as much as ..33nm from the GPS position. Also the beacons shown may or may not exist due to cyclonic weather. What does exist still is the reef system and is quite a good idea to avoid. We watched 2 rather expensive yachts have arguments with a reef and heard of a number more. Reefs are not much of a problem on nice sunny days but when overcast it may become impossible to "eyeball". What to do depends upon the circumstances. However using GPS alone would shorten the cruise and you wouldn't have the bother of sailing home. jofra |
"Jofra" wrote in message ... Enjoying your little tiffs you guys. Obviously you both have a certain amount of sense as you are both still around or else the gods have been particularly kind.... Just come back from Fiji where we stayed for several months. Many of the charts predate GPS's and the result is that they may be out by as much as .33nm from the GPS position. Also the beacons shown may or may not exist due to cyclonic weather. What does exist still is the reef system and is quite a good idea to avoid. We watched 2 rather expensive yachts have arguments with a reef and heard of a number more. Reefs are not much of a problem on nice sunny days but when overcast it may become impossible to "eyeball". What to do depends upon the circumstances. However using GPS alone would shorten the cruise and you wouldn't have the bother of sailing home. jofra 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 |
Several students of DeVry Institute of Technology in Calgary, Alberta, Canada did just that with
four GPS receivers, a computer, and some specialized software. Four inch accuracy. **No kidding.** I don't know if they had DGPS units for the experiment. The experiment snowballed from an earlier experiement that won them some sort of international championship in 2001 when they got an automated, computer guided model helicopter to lift off, fly 3 meters and hover over a four inch target, hook onto it and then fly back and land. No manual control what-so-ever. Pretty neat if you ask me! (But I heard they had to drive at only a walking pace). "Jack Dale" wrote: How many out there are prepared to drive their car using GPS only? |
On Mon, 17 Jan 2005 19:45:54 -0600, Maynard G. Krebbs
wrote: On Sun, 16 Jan 2005 23:34:23 -0500, Rodney Myrvaagnes wrote: On Sun, 16 Jan 2005 23:17:11 GMT, "Roger Long" wrote: 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. Can't tell what you are talking about. Both the QE2 and Nantucket shoals incident are quite recent. The QE2 was a chart problem, since corrected, and had nothing to do with autopilot or any other automated gear. I heard they had more of a squat problem. As in they forgot to figure in the ship's squat at their speed over the shoal. Mark E. Williams Right! The pilot and the long-time skipper colluded to make an elementary mistake. Look at the chart, before and after. It is possible that squat may have lengthened the tear in the hull, but if the chart had been correct they wouldn't have touched at all. 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 |
On Tue, 18 Jan 2005 05:13:19 GMT, "Richard P." wrote:
Several students of DeVry Institute of Technology in Calgary, Alberta, Canada did just that with four GPS receivers, a computer, and some specialized software. Four inch accuracy. **No kidding.** I don't know if they had DGPS units for the experiment. The experiment snowballed from an earlier experiement that won them some sort of international championship in 2001 when they got an automated, computer guided model helicopter to lift off, fly 3 meters and hover over a four inch target, hook onto it and then fly back and land. No manual control what-so-ever. Pretty neat if you ask me! (But I heard they had to drive at only a walking pace). "Jack Dale" wrote: How many out there are prepared to drive their car using GPS only? I live in Calgary. I hope they send out a notice to drivers when they do it. 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 |
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. otn |
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 |
On Tue, 18 Jan 2005 17:59:40 GMT, otnmbrd
wrote: 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. ================================ There are fixed errors also. I live on the south side of a 120 foot canal. Four different WAAS GPS units consistently show the boat docked on the north side. Most likely chart error but who knows? |
| All times are GMT +1. The time now is 01:25 AM. |
|
Powered by vBulletin® Copyright ©2000 - 2025, Jelsoft Enterprises Ltd.
Copyright ©2004 - 2014 BoatBanter.com