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Old 11-02-2006, 22:23   #31
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Sounds like you ahve a harder time than I do. Nah it's not so bad now I am used to it. But then, I haven't meet one of the really big Mussle Boats yet. These guy's are a little arrogant and don't slow down. Well I'm Ferrocement, so I don't think I will be the only one to come off bad if they hit me. It might give im a wake up.

"Unexploded Munitions" Holy crap Batman. At least they bury that sort of stuff over the shelf here in NZ waters.
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Old 11-02-2006, 22:46   #32
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A little story here about unexploded munitions. They bury them deep now but that wasn't always the case. A few years back I was doing a relief trip as engineer on a trawler up in the Bay of Plenty. We were skirting the edge of an old ammo dump in 400 metres of water. Part way through the trip we picked up an old depth charge in the net and it ended up on deck. The crew had a system of boards ready to get the things back over the side as it had happened before. Well, as they rolled it down the chute and it fell into the water they all ducked down behind the bulwarks. I asked them why they did this and they said it was in case it detonated!! I just about injured myself laughing as I tried to explain to them that these things are designed to rupture pressure hulls on a sub so breaking the back of a fishing boat shouldn't pose too much of a problem and ducking wasn't going to achieve much.
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Old 11-02-2006, 22:52   #33
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They were probably worried about a 5ton motor block flying through the air Pete.
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Old 11-02-2006, 22:59   #34
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Explosives dumping ground, hey ain't that just a "self Policing Marine reserve"?
Mate fishing must have been real bad if you started skirting something like that. Of course, that brings up whole new issues if it's trawling dumping grounds in French Polynesia.
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Old 12-02-2006, 00:24   #35
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Years after World War 2.

Alot of fishing boats have caught mines in their nets. And some of them sunk because of them mines.

Also some of them mines washed ashore in various places. So it makes you wonder how many there might be still out there in the oceans?
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Old 16-02-2006, 17:16   #36
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Only the ENC charts are internationally legal for ships required by law to maintan charts. The US ENC charts are identical to the NOAA raster charts in terms of accuracy PLUS they can be "patched". They are the only legally acceptable electronic charts in US waters. This of course relates to commercial vessels.

The idea that paper charts are more accurate than electronic is false. The idea that you can enlarge a digital chart beyod it's accuracy is clearly correct. Your GPS isn't asured to be that accurate as well. Things move and depth data is not all that reliable depending on where you are. There is a great deal of intangible data to be delt with. The format does not make it better or worse.

Electronics do fail and I do prefer a paper chart entering harbors for the first time. I like to hold it in my hand.
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Old 18-02-2006, 10:22   #37
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Quote:
Zach once whispered in the wind:
They've also turned off the GPS for the area... thats not nice at all. They did it for the week of the Big Rock here in NC last year. Someone must have been betting on folks that use loran cordinates!
Zach - you're going to have to explain this one. GPS uses orbiting satellites, so I don't believe that GPS can be "turned off" in a specific area. Of course satellite geometry and satellite outages can make fixes less reliable in specific areas, but most GPS units have the capacity to rate the quality of the fix.

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Old 18-02-2006, 10:57   #38
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Pblais once whispered in the wind:


Electronics do fail and I do prefer a paper chart entering harbors for the first time. I like to hold it in my hand.
Same here. Because entering a harbor is usually a 360 degree, 2 dimensional visual experience, I also prefer to be able to line up the paper chart with my heading in the cockpit and be able to quickly glance at it. My plan, now that I'm "paperless" is to print out these types of charts (harbor, general overview, etc...) prior to departing. I'm meticulous when it comes to planning my route and putting in fail-safes. I like to be able to just follow the instructions I laid out for myself the night before, and not think while piloting.

Also, if someone else is taking the helm for a watch, it is a good idea to have a regular system in place so they could pick up the helm and know exactly what to do at any given time - even entering a harbor.
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Old 18-02-2006, 10:59   #39
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GPS uses orbiting satellites, under the control of the Interagency GPS Executive Board (IGEB). The IGEB is co-chaired by members of the Departments of Transportation and Defense, and comprised of members of the Departments of State, Agriculture, Commerce, Interior, and Justice as well as members from NASA and the Joint Chiefs of Staff. It allows for both civil and military interests to be included on all decisions related to the management of GPS.
At one time, Selective Availability (SA) was used to protect the security interests of the U.S. and its allies by globally denying the full accuracy of the civil system to potential adversaries, but, by order of the President of the United States, the use of Selective Availability was discontinued on May 1, 2000. It is not the (current) intent of the U.S. to ever use SA again. To ensure that potential adversaries to do not use GPS, the military is dedicated to the development and deployment of regional denial capabilities in lieu of global degradation through SA.

Who knows what a government, faced with a rogue nation (with WOMD capabilities), bent on aggression against that government, might decide is in itís national interests ? Not I.
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Old 18-02-2006, 12:06   #40
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regional denial of gps

Gord - you never cease to amaze with your info and insights. I gather from the way you worded it, that it is still in development. Maybe Zach experienced a test run. Given that there are other options (glonass and galileo) I would think the US military/govt would be developing jamming technology that could be deployed in the vicinity of vital potential targets, rather than selectively shutting down satellites. Since it would require shutting down anywhere between five and twelve (guesstimated) satellites to deny a GPS fix in a certain location, the resultant interruption would be over a significant portion of the planet. Given that US and allied forces are so widespread, I would think it unlikely they would deny GPS to them as well. I believe DoD has reserved the right to fire up SA again at will, but given the low-tech solution of DGPS pretty well nullifies the SA dithering, there really would be no advantage. Any other thoughts on the subject?

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Old 18-02-2006, 12:14   #41
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The US government has the right to shut down the GPS satellites. (Considering that this system is a "American Invention." And American owned.)

The Department of Defense (DOD) could make the call to shut down, or simply deny users to access GPS satelites. Due to the nature of certain combat campaigns? Or possibly security issues?

The US government reserve that right. And since they were the ones who put them up in orbit around our planet, can do so. Without warning. Anytime!!
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Old 18-02-2006, 17:04   #42
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the big off switch

CaptainK - you were in the Navy; are you familiar with the term "emcon"? It's short for "emissions control" which was used by most navies for the past half century. It involved a lot of sailing with lights turned off and radars shut off, so that the enemy couldn't see you. The downside, is that you could not see the enemy. But that was the strategy of the day, given the state of technology. I think the USN pioneered the concept of the overt battle force, radiating on absolutely everything, so that if someone shot so much as a BB at them, they could see it and blow it out of the sky somewhere over the horizon. Given that all the US forces are dependant on GPS positioning, as are their cruise missiles, I cannot imagine they will shut it off - it would be like going back to the days of emcon. Worse still, their enemies could be using glonass or hyperfix or somesuch, which would give them the advantage. Imho.

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Old 18-02-2006, 17:17   #43
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I meant to say Lodesman.

That the US could divert the GPS system to their use. And shut down the rest.

But, I'm a little rusty about the most recent GPS technology out there now? But, in the past. I know for a fact that the military had only sole access to the GPS system.

Only within the past decade, have the civilian sector has been getting the privilage. Of being able to use GPS. And that yes, Lodesman. I know all about "emcon." I believe that's the correct term. I never dealt with the ships' bridge, or the ships' CIC (Combat Information Center) operations.

My job never has anything to deal with Bridge operations!!
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Old 18-02-2006, 20:29   #44
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Navigation

Back in 1968 in Honolulu a lot of my neighbours were in the Navy.
They would go out on maneuvers. One boat would go a ways offshore and try and make it back to the Island with out getting caught by other boats. When one of my navy neighbours missed another cracking good piss up and showed up days later, I asked him, " where were your the last few days " " Lost " he said.
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Old 18-02-2006, 21:57   #45
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CapnK - I believe that the US Congress only approved the billions of dollars for GPS on the condition that it would be available to commercial civilian users. Since GPS came into being in the mid 80s, it has been available to the public. The military has had sole access to the PPS (precise positioning system) which uses a second ciphered signal on a different frequency. The second freq allows an actual correction to the atmospheric conditions (ephemeris?) and is therefore more accurate than the standard single freq system which uses tabulated correction values. The ciphered signal used to also carry the correction to the clock dither - the deliberate error input as selective availability(SA). I believe also that the precursor to GPS - Navstar Satnav was military-use only. I can tell you I don't miss that bit of gear - 90 mins to 6 hours between fixes, huge errors, reliance on Omega for the DR...

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