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Old 30-07-2008, 11:14   #16
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Heres how I'd do it:

When I come up to an inlet, I'd get parallel to it, note the compass heading, look at the chart and see which inlets point that direction. Walk a set of parallel rules down to each possibility. When you I find the one that looks right...

Drop a lead line, and see if the charted depth matches where I think I am. (I don't have an electric depth sounder anyway...) I always figure the closest ground is whats under the boat... or at least its what I find when I'm not looking for it.

Drop in neutral, or lower the sails... point the bow towards one bank, jot down the bearing. Point towards the other side, jot down the bearing. Plot the lines, and where they intersect... and thats where I might be.

Measure the distance on the chart in nm, cut out a piece of paper the distance from the boat on the radar to the shore, divide it up and you've got a distance scale for the current settings.

With no lead line, and uncertain of how well the radar's displayed heading line is correct I'd run a compass course perpendicular to the inlet and see if the banks of the inlet pass at 90 degrees, or 3/9 o'clock on the radar screen.

With that information, and the assurance that the radar is more accurate than my hand bearing compass abilities... I'd be looking for channel markers or sea buoys to go up and physically lay eyes on them... for belt and suspenders approach. Bonus if theres a gong near by...

Then as I continued poking along, I'd be on the lookout for any big tall pointy things on the chart, or prominent land masses that overlap so I can use them for ranges, and add more more lines of position until I get a fix.

Might not be the fastest way... but I think it'd do the trick.
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Old 30-07-2008, 11:33   #17
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Was going to respond yesterday along the lines of "wait for the fog to clear" - but I see that has been disallowed (and I guess DIY appendix surgery is disallowed for some reason - I'd be game to try )

Have used a Radar, but never on my own boat and never seriously (a 5 minute looksee and "oh look, their's the coast - doesn't look much like the Chart" etc etc).

And of course never been in this part of the world (on a Boat).

So I figure that makes me an "expert"

Sounds like to me that their are shipping lanes around the vicinity, in Heavy fog (or any fog) I would hesitate to cross a major shipping lane (without a radar - I understood!) but lets pretend I can read a radar screen and can tell a Freighter from a wave top I should be able to at least roughly plot a shipping lane from a fairly safe distance by tracking vessels. On it's own won't be a great deal of use, but once the coast appears on screen it may rule out a few places / provide some comfort for the Dead Reckoning.

As temp passé well familiar with closing to a foreign coast that doesn't look very familiar and not being too sure of whether to turn left or right - tended to DR one way or the other, so the choice when seeing (or in this case Radaring the coast) was clear. I guess coming in from the Pacific the room for error is somewhat larger than my past experiances. But notwithstanding the urgency of the appendix stuff I would err on the "slowly slowly catchy monkey" side of things rather than risk heading off in the wrong direction. It is always easy to see what you want to see.........

On the basis that I do have a paper chart (or has that gone in fire as well? ) I would check with a lead and line to see if I can pick up when the water shoals, how much and where and see if I can pick up a contour line (albeit I have vague memory that the Water is deep deep, until it hits the coast - which has plusses as well for navigation ). Radar should hopefully also pick up some coast at a safe distance, no matter not identified. and should be able to use your main compass (I guess if you have found America by DR you do still have one) to plot your course down the coast in relation to the shore at a constant distance. Every little bit helps.

I dunno if you guys still have lighthouses with fog horns in the area, but would be nice if you had! If this is a commercial shipping area I would expect that their would be at least some bouys / marks around before the navigation got too complicated inshore (and with good radar reflectors), be great if I could pick one up on Radar or simply motor up to it to 100% confirm position and then DR from thereon in - with the Radar as backup for Vessels and any coast and any further bouyage. If I could pick up a fixed object should also to check the Radar, no matter what the swell.

Ideally would like to follow someone of a similar speed in or at least use them as a guide - but of course even the locals get stuff wrong, and no guarantee you are following a local........

The above is a long way around of saying a) I know sh#t about maths (albeit am ok enuf with English, hence the "s" in maths ) and b) am not much cop with a Radar....even if working perfectly I would not be capable of relying solely on it - and with a boat that badly damaged with fire, even if I was an expert I can't say I would want to rely solely on it.
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Old 30-07-2008, 12:47   #18
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The only problem is that the track ball and knob for your VRM feels “mushy” so you do not know if the readings are accurate.
Is this a trick question?

The range displayed is calculated according to where the computer put the range marker. It doesn't matter how wobbly the knob/track ball is, except to the extent that an intermittent knob makes it difficult to put the marker in the right place.

The fixed rings on the screen are placed according to the current range setting, so even if you can't move the range marker, you can still interpolate between the rings. e.g. On my radar, the rings are spaced every 0.5 nm when on the 2 nm setting, so something half way between the second and third ring is about 1.25 nm away.
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Old 30-07-2008, 12:52   #19
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Chase down two marks, like ODAS 46026 (16-18 miles offshore) and Amphitrite Point, where you can sail between the two marks. When you have them both abeam, note the range to the one and the range to the other. Add 'em up, and if it totals the same as the charted spread between the two points, your radar ranges are probably correct.


If the radar is fubar, try sailing in a triangle pattern (120 degree turns with reasonable size legs of same time/distance between each) and hope that someone at vessel traffic control or another radar operator recognizes the aviation distress pattern used by aircraft with no communications systems. The "odd behavior" might get assistance from any government or SAR assets watching over the area as well, any military types watching the approaches should spot it.
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Old 30-07-2008, 12:54   #20
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Like some others my acquaintance with radar is limited and I have no knowledge of the location selected for the problem, therefore didn’t contribute, however I thought the ‘running fix” solutions by most were viable, but omitted an important item which Zach and David provided, the depth/underwater feature which, with the other available information, would allow a pretty good DR, to begin the process of safely reaching port

Regards

Alan

PS The idea of providing these nautical brain teasers is a good one.
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Old 30-07-2008, 12:55   #21
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and I guess DIY appendix surgery is disallowed for some reason - I'd be game to try
The appendix has no known function except to get infected, burst and line your surgeon's pockets for removing it.

As the pain of a burst appendix is awful, it's best to prevent it getting infected entirely.

Drink a glass of Easy-Off Oven Cleaner (caustic) each morning to kill any germs that may be in your gut, keeping your appendix healthy and happy.
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Old 30-07-2008, 13:10   #22
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As the pain of a burst appendix is awful, it's best to prevent it getting infected entirely.
I was around 10 years old when mine was removed (before it burst). I recall that it hurt like fook even without bursting


PS I also like the teaser idea (even though I strongly suspect I won't understand the answer to this one ).
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Old 30-07-2008, 14:15   #23
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OK, again forget the VRM business. Let's try something else (lateral thinking!)

Head down the coast, standing off a safe distance, and use your radar to look for a RACON buoy, such as the RACON buoy near Swiftsure Bank, at the entrance to Juan de Fuca Strait: [Y “J” Fl Y 2.5s RACON (.---)]

RACONs transmit their identifying letter in Morse Code, so the one above would show as a bright Morse "J"( .--- ) on the radar screen. If you've ever seen one of these things light up your screen, you know there's no mistaking it for anything else!

Wha da ya say, Pelagic?
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Old 30-07-2008, 14:42   #24
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Wow! A couple of you guys got a bit hot, just remember this is only a game and it is supposed to be fun….. but challenging.

In the PNW…. commercial and pleasure boats ply the inside passage for days in zero visibility thru narrow passes with strong currents. They perform blind pilotage, using radar alone and a technique called “parallel indexing,” which relies on running courses that keep you a safe distance from charted dangers by using offsets from strong Radar targets (your CPA’s). All of this is prepared on the paper chart and you often use radar transits to confirm your position and equipment.

For it to work well you need very accurate VRM’s and the ability to float your EBL’s to a precise distance in tight quarters. Also it helps if you have a mountainous coastline as BC does which gives you sharp targets.

Many experienced answers especially Zach who understood the first challenge was to find out where you are by comparing and measuring inlets, but that wasn’t the question!

The question was: So how do you prove that your VRM is correct?

David M’s first answer was the closest and was actually how they did it before VRM’s were installed in Radars.

Coot, you are right about the Fixed rings but wrong about the VRM knob which is like a potentiometer that paints a sliding ring on any radar display scale. They do fail with rough use which I have confirmed at boat shows where kids or Joe Public have twirled them to death.

The answer to how you verify the VRM is actually very simple.

As Coot explained the Fixed rings are painted on by the radar’s processor and are not subject to mechanical failure.

You turn up the brilliance on the Fixed rings then on different scales confirm that the VRM matches the Fixed Ring reading exactly when the leading edge of the VRM just touches the inside of the Fixed Ring.

Experienced masters make that a standard check for any watchkeeper starting his watch, when operating in reduced visibility and the skipper expects to see it logged.

So who is next with a challenge?
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Old 30-07-2008, 15:50   #25
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Old 30-07-2008, 20:59   #26
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Coot, you are right about the Fixed rings but wrong about the VRM knob which is like a potentiometer that paints a sliding ring on any radar display scale. They do fail with rough use which I have confirmed at boat shows where kids or Joe Public have twirled them to death.

The answer to how you verify the VRM is actually very simple.

As Coot explained the Fixed rings are painted on by the radar’s processor and are not subject to mechanical failure.
This may have been the case with old-school radars, but I think with most of the radars manufactured in the last 30 years, the VRM and range rings are both plotted "synthetically" and as Coot said a sloppy knob would not affect the range. Seems to me if you consider a very accurate VRM to be necessary for plotting your PIs, then your biggest concern should be radar range error, which will affect VRM, cursor, and range rings. There are limited options for checking this in the scenario you suggested - that's why I asked about the double echoes.

BTW, I wouldn't consider the Strait of Juan de Fuca to require pinpoint accuracy. From the position where you lose your instruments, you should be able to DR to Vancouver Is, then follow the coastline SE to JDF at a safe distance, say 10 NM.

JMO,

Kevin
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Old 30-07-2008, 22:25   #27
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Sorry Keven it actually does happen (albeit rarely) and I have discussed this with Manufacturer’s service managers at Trade shows (back in 95) where they explained that the knob is a potentiometer and subject to misalignment if heavily abused.

I made a mistake in making this challenge too convoluted with my wounded landfall scenario in the fog, so everybody forgot the real question. But in reality you might find yourself feeling your way into Tofino, Uclelet or even to the dock at Neah Bay and the VRM would be needed in zero visibility for that scenario.

I had been doing that for years prior to GPS so it does not worry me if I can trust my radar.

I’m ready to be stumped and learn something…whose next?
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Old 31-07-2008, 05:54   #28
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Sorry Keven it actually does happen (albeit rarely) and I have discussed this with Manufacturer’s service managers at Trade shows (back in 95) where they explained that the knob is a potentiometer and subject to misalignment if heavily abused.
Okay - but obviously not the case where the VRM is controlled with a trackball, pushbuttons or a toggle switch. Anyway, it's been a good discussion with a lot of good opinions - perhaps we should dissect some of those points too, if we are to maximize the opportunity to learn. For example, Hellosailer did an excellent job of describing the "two-mark" method of determining range error - although I would refrain from using any buoy for this purpose as they are not truly in a fixed position. Hud's idea was pretty good too, but the transponder-pulse of a RACON buoy doesn't necessarily correspond with its alphanumeric identifier. Buoy "J" a cautionary buoy marking the TSS in Juan de Fuca actually has morse "O"(---) as its RACON.

Kevin
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Old 31-07-2008, 06:40   #29
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Agreed Kevin, many good points which in a way does favour describing a humanistic scenario… to get our problem solving juices and immagination flowing.

I think when the Radar showed that you were closing in on the mountain ranges you would start hunting for a really distinctive radar return from the shore and make a determination from a safe distance.

At the same time hoping you encounter a stationary fishing boat that you could safely approach in the fog and confirm your position.

As you are probably being tracked by Vessel Traffic Management” as a suspicious offshore unknown vessel, the fishboat could also inform say “Toffino Traffic” of your situation and let other vessels know that you have no communications. Traffic would also keep a close eye on you via their powerful radars

Better than the Coast guard coming out to meet you with a suspicious attitude.

I would like to hear someone else give us a different challenge on this thread just to see how this game evolves.
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Old 31-07-2008, 08:01   #30
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This one will be easy for many I think, and may have a few different answers. I hope it is at least a worthwhile exercise for new sailors.


You’re sailing south from Bermuda on a delivery of a 40’ sailboat in late July, because the owner of the boat is anxious to have it in Antigua for Aug. 1. Your crew is a group of 3 Swedish swimsuit models, looking for adventure on the high seas and eager to get to Antigua for an upcoming photo shoot. You’re halfway between Bermuda and Tortola steering 170 degrees. You’re enjoying your daily check of the weather while sailing through a small rain squall.
Your ears perk up when you hear, “All mariners be advised, there is a strong low pressure south and East of Bermuda intensifying rapidly, and expected to reach hurricane status at any time. It’s currently located at….” Crack!! Boom!! Lightning just took out all of your electronics. (ok, a little far fetched, but we have to get the instruments and electronics out of the equation) One of the girls was baking a quiche and had taken the handheld vhf and gps out of the oven, so even they are toasted. Being the calm Captain that you are, you take a closer look at the conditions outside. You see a large long swell from the SE at a rate of 4 per minute. The girls marvel at the cool looking ‘Mares tails’ in the sky, long windswept cirrus clouds. The wind is very light from the NE at about 5kts.
12 hours later the wind has started to pick up, still from the NE, to about 15-20 kts. You notice that the clouds are starting to come in bands. You tap the glass of the barometer and notice that it has started a precipitous drop.
Several hours later the wind has increased to 35kts, and only shifted slightly to the ENE. The clouds still come at you in heavy bands, the seas are starting to become confused. You are still sailing south. The girls are beginning to get nervous, and even more disconcerting, they are starting to layer on heavy amounts of weather gear">foul weather gear over their bikinis. What’s going on? Where is the storm? Should you change course? If so, what direction?
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