First of all: this is NOT a debate about the merits of keeping c-nav around in the 21st century. I’m pro-c-nav and nothing is going to change my mind. What I do want to talk about is a specific problem with using c-nav as a backup. We all know that c-nav is still around because everyone’s GPS unit craps out once in a while, and there’s still a chance that one day some idiot is going to shoot a satellite down and we’re all going to romping around out there like chickens with our heads cut off. I agree with this line of reasoning and continue to support c-nav because of it.
So here’s the problem: whenever we do c-nav on a ship these days we get our accurate time to do it with FROM THE GPS UNIT. So when the GPS goes down how are we going to do c-nav? I know some ships have carriage requirements for sextants, nautical almanacs, 229 tables, etc… but is there a carriage requirement for marine chronometers? Obviously we need some kind of accurate time keeper but what would the average ship do for accurate time keeping ability without a GPS?
And by the way, if the Navstar + Glonass + the future Galileo is too suddenly fail one day, I would think that the least of our problems would be to know the ships position.
And by the way, if the Navstar + Glonass + the future Galileo is too suddenly fail one day, I would think that the least of our problems would be to know the ships position.[/QUOTE]
Atomic clocks are great but ships do not carry them. Go back to Norway.
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[QUOTE=Robert;132378]Time tick from WWV or WWVH[/QUOTE]
True, for sure, but you won’t be taking a sight by the sound of a time tick. Something needs to carry the time in between. I guess you’d just have to update your quartz watch once a day, annoying and tedious, but I guess it works.
I agree with getting the time tick. You probably don’t even need a fancy marine chronometer, just make sure your watch, or the clock in the chart room, is synced up.
Hey C.Cap, let’s have some pictures of that Hamilton Mark 21 I know you have. Did you ever fit it to the new box you got for it a while ago? How much did you pay for that thing anyway?
True, for sure, but you won’t be taking a sight by the sound of a time tick. Something needs to carry the time in between. I guess you’d just have to update your quartz watch once a day, annoying and tedious, but I guess it works.[/QUOTE]
The daily rate (the amount the watch gains or loses a day) of a inexpensive quartz watch is going to be stable enough to use for navigation. You just need to determine the rate same as was done with the old mechanical chronometers. You would have to get the rate over several days as it is likely very small.
Many years ago we sent one of our bridge chronometers ( a Chelsea I think) to Captains Nautical in Seattle be repaired. They sent us back a battery operated quartz.
[QUOTE=Chief Seadog;132433]Many years ago we sent one of our bridge chronometers ( a Chelsea I think) to Captains Nautical in Seattle be repaired. They sent us back a battery operated quartz.[/QUOTE]
I hope you got a fat wad of cash with it! The Chelsea was probably worth a hundred times what the quartz was worth, and then some!
[QUOTE=PaddyWest2012;132434]I hope you got a fat wad of cash with it! The Chelsea was probably worth a hundred times what the quartz was worth, and then some![/QUOTE]
My $30 Casio wristwatch works just fine. The error over a month is negligible. Cellphones give very accurate time
[QUOTE=PaddyWest2012;132434]I hope you got a fat wad of cash with it! The Chelsea was probably worth a hundred times what the quartz was worth, and then some![/QUOTE]
A $30 Mickey Mouse watch, provided it uses a quartz crystal for timing, is likely going to be both more accurate and more stable then a mechanical chronometer. Both accuracy and stability can be checked and verified using radio time tick at appropriate intervals.
If you want to spend more money buy more $30 watches.
[QUOTE=Kennebec Captain;132442]A $30 Mickey Mouse watch, provided it uses a quartz crystal for timing, is likely going to be both more accurate and more stable then a mechanical chronometer. Both accuracy and stability can be checked and verified using radio time tick at appropriate intervals.
If you want to spend more money buy more $30 watches.[/QUOTE]
I’ve sailed quite a few delivery jobs in the '70s. Each vessel was equipped with a Chelsea chronometer with the rate checked and logged with WWV or CHU. BBC also has time calibration on the hour. The favorite tool of the captains and mates was a large battery powered kitchen clock.(before quartz clocks were available) The clocks were calibrated just before nautical twilight or sun lines.
I was curious about that myself so I looked into it. According to the people who make $30 mikey mouse watches they’re accurate to +/- a second a day. That’s quite an error after just a couple of weeks.
[QUOTE=PaddyWest2012;132450]I was curious about that myself so I looked into it. According to the people who make $30 mikey mouse watches they’re accurate to +/- a second a day. That’s quite an error after just a couple of weeks.[/QUOTE]
A mechanical marine chronometer typically would have a daily rate of at least 0.5 seconds, a daily rate of 3 or 4 seconds was not uncommon. A typical daily rate for a marine chronometer is probably between 1 and 3 seconds. Total accumulated errors would be large, Look up some typical problems in the nav text.
Dutton’s says a quartz chronometer rate is about 0.01 per day.
.The standard for a cheap quartz watch is 15 seconds a month. Most are much better. I set my Casio a couple times a years, it’s usually off by a only few seconds.
But…what matters is not accuracy but the daily rate and stability, the change in the rate. If you know the error on a given day and the daily rate you can compute the current error. Even a Mickey Mouse quartz watch is going to be very stable (daily rate has very small variation), much more so then a mechanical chronometer
As long as you know the error at any given day and the daily rate you can convert from CT to UTC and get a time accurate enough for navigation.
Back in The Day we just got a digital watch and kept it near the radio below. We would tune in WWV once or twice a day and log the error. Seemed to work out fine.
I dare say that any licensed deck officer (especially those standing bridge watches and making regular deck log / bell book entries) who do not wear a watch that is both accurate and precise enough to be used for celestial are probably not the ones to be trusted for position fixing if all the gadgets get shut off.
I would rather have a $30 Casio in a box than one more damn correction log to keep up with for port state control to come looking for.
[QUOTE=PaddyWest2012;132370]First of all: this is NOT a debate about the merits of keeping c-nav around in the 21st century. I’m pro-c-nav and nothing is going to change my mind. What I do want to talk about is a specific problem with using c-nav as a backup. We all know that c-nav is still around because everyone’s GPS unit craps out once in a while, and there’s still a chance that one day some idiot is going to shoot a satellite down and we’re all going to romping around out there like chickens with our heads cut off. I agree with this line of reasoning and continue to support c-nav because of it.[/QUOTE]
The new ship here is fitted according to the reported increase of knowledge among mankind. Namely, she is cumbered end to end, with bells and trumpets and clock and wires, it has been told to me, can call voices out of the air of the waters to con the ship while her crew sleep. But sleep thou lightly. It has not yet been told to me that the Sea has ceased to be the Sea.
