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#121
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Jim Donohue wrote:
So we actually agree? The system was seriously flawed but the Crew should have caught it anyway as there were multiple and pretty obvious indications that competent sailors should have caught. Jim G To a point. I don't think the system was "seriously" flawed, since SOP and good training should have caught it, with the system as is/was. I tend to use "competent" in a stricter sense .... they may well have been competent mariners, but they sure screwed up. If I have a beef, it would be (as expected) with simply doubling up on GPS, especially on approaching Nantucket. Although a 2nd GPS would be nice (and generally standard), I would still prefer that double checks would involve different systems..... Radar, Loran, Fathometer, Visual..... when available. otn |
#122
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Jim Donohue wrote:
As I projected responding will do little good. The way they are fixing this Jeff...is to plug in multi GPS. Don't you think it odd Jeff that the fix for over-reliance on GPS by making the system even more dependent on GPS. Where does it say that? And you do read strangely...multiple independent position receiver inputs...turns automatically in your mind to multiple independent sources...I wonder why this is? Like your use of "form" could it be you can't find the right language so you substitute your own? Two identical GPS's are not "independent". They may help in some failure modes, but certainly not all. However, the recommendations also talk about the need for for techniques other a large pile of GPS units. In particular, the cruise lines were advised to: "ensure that all watch officers adhere to sound watchstanding practices and procedures, including using landmarks, soundings, and navigational aids to verify a vessel’s position, relying on more than one source for position information, and reporting to the master any failure to detect important navigational aids." You seem to keep forgetting about this part. This was the specific advice to the cruise lines, and by implication, their ships' officers. All of the other advice had to do with the design of the hardware, which, while somewhat interesting, is not directly related to the actions of the deck officers. So what lesson can the typical daysailor/coastal cruiser take from this? Is it that they should always run two GPS's and continuously compare the answer? I don't think so, though there may be time when its prudent to have a second one handy. The advice is clearly to not be so over reliant on a single source, and to use traditional piloting techniques: landmarks, soundings, navaids. One of the reviews of this grounding pointed out that weather was in fact a factor. It was so good that the crew was complacent. Given your line of reasoning we could simple claim the good weather made the crew complacent causing all of the other items that you ascribe to over-reliance on GPS. Kind of silly but then so is your interpretation. Why not presume the NTSB people meant what they say? Why do you ignore what they say? Their specific advice to the seamen is to remember to use piloting and not to be so reliant on a a single source for position. |
#123
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There actually was a pretty big error...the technique used by Raytheon to
flag bad data was different then the one the bridge system was using to respond to bad data. In my view as an electronic systems guy that was a very big error...particularly in a system that could lead to a people/property hazard. I agree though that it should not have been so significant because there were multiple other ways to catch it in this case. But I could postulate cases where it could be quite serious quite quick. In the heavy boat business I would have thought two or three GPS receivers would be standard aside from any additions like LORAN. Three is a little magic because it almost always allows you to isolate the mis-behaving unit. I don't think you can integrate radar into such a system. You can show the picture or the picture enhanced but the software to match a view to a map would be very difficult. If however you know where you are (or think you do) it is possible that you might match the patterns. Cross check perhaps...but quite sophisticated software. Of course your people can cross check radar and fathometer. If you can keep them focused to do so. A known hard problem. Jim "otnmbrd" wrote in message ink.net... Jim Donohue wrote: So we actually agree? The system was seriously flawed but the Crew should have caught it anyway as there were multiple and pretty obvious indications that competent sailors should have caught. Jim G To a point. I don't think the system was "seriously" flawed, since SOP and good training should have caught it, with the system as is/was. I tend to use "competent" in a stricter sense .... they may well have been competent mariners, but they sure screwed up. If I have a beef, it would be (as expected) with simply doubling up on GPS, especially on approaching Nantucket. Although a 2nd GPS would be nice (and generally standard), I would still prefer that double checks would involve different systems..... Radar, Loran, Fathometer, Visual..... when available. otn |
#124
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Jim Donohue wrote:
In the heavy boat business I would have thought two or three GPS receivers would be standard aside from any additions like LORAN. Three is a little magic because it almost always allows you to isolate the mis-behaving unit. As stated, two are standard ...... three is overkill. After all, with multiple radar, Loran, fathometer, celestial capabilities, etc., they have any number of proven methods to navigate to their destination with the needed accuracy, and it's not like a GPS unit is all that frequently breaking down. I don't think you can integrate radar into such a system. You can show the picture or the picture enhanced but the software to match a view to a map would be very difficult. If however you know where you are (or think you do) it is possible that you might match the patterns. Cross check perhaps...but quite sophisticated software. All ready being done. I was looking at a chart overlay on a Radar, yesterday. Noted that the plotted position and radar position for the Seabuoy had a significant (to me) difference ( we can all understand the possible problems this could create). I didn't have time to determine if the difference was a plotting, alignment, or off-station problem. Later on I was looking at a chart plotter (Based on Admiralty charts) and noted that a particular Range line showed slightly right of channel centerline. In actuality, it's slightly left. EG In both cases, since I was employing other methods as checks, neither problem (admittedly both were extremely minor and should not have created a problem even for someone unfamiliar with the area) caused me any grief and were filed away as "possible discrepancies to look for". Of course your people can cross check radar and fathometer. If you can keep them focused to do so. A known hard problem. G Not really. If you consider the number of ships at sea on any given day, plus mileage traveled and the overall accident rate (which no doubt has plenty of room for improvement) then the percentage of failures is fairly small, coupled with the fact that for all the cases such as the Royal Majesty that we hear of, are the many cases that the problem was observed and corrected, so consequently, never heard of. otn |
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