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Old 22-05-2006, 18:17   #1
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How Come

Navigation and weather are the two most important issues on any passage. How come no threads here?
I suspect because they end up in discussions about electronics. I'd like to start this thread with a discussion of celectial navigation, ded reckoning, but heck there's no more dedicated electronic navigator than I. So I thought I would kick this thread off with a discussion of AIS on yachts. For a starter I have published a web page on my implementation of AIS at http://www.svsarah.com/Sarah/Upgrades/AIS.htm

Comments and questions are welcomed.

John
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Old 22-05-2006, 19:04   #2
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There was an argument recently at my club regarding AIS as another intrusion into ... It seems that there is some pressure to implement AIS in North America/Mexico. As for the merits I am personally on the fence.

With that said I am interested more traditional forms of navigation. Also I would like to hear tips for using the sextant in applications other than celestial nav.

I spent this last weekend sailing with a guy new to our bay. Around here we often use the bridge method: Keep that bridge on your right until you see the bridge over the channel. We spent some time working out chart to landmarks.

In any case it seems that a lot of people I know sail as if they are in a constant fog even on a clear day. They go from waypoint to waypoint keeping a lookout with a radar. Which is all OK but I'm with you John let's talk dead reckoning. I need to steal some good ideas.
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Old 22-05-2006, 19:19   #3
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Smile AIS Experience

I just bought an SR-161 AIS package and integrated it with Nobeltec VNS 8.1. Using a VHF antenna on a rail mount works great-although testing it from my house (on hill) got ships at 50nm, still get ships at 10+nm. Being in San Diego Bay, immediate use is identifying Navy ships and cruise ships that are departing and will need to be avoided. When out, provides much better ship tracking than ARPA, plus ability to see ship names gives a real boost to calling them if necessary-USCG and VTS record conversations, and call by name makes sure the "I didn't know it was for me" doesn't work. Great gadget at a very low price-<$250 including antenna (but not VNS, although a copy of Seaclear is included for free). It's nice to see something that works like it's supposed to.
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Old 22-05-2006, 20:04   #4
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AIS Question

I just bought an AIS unit...still in the box.

My next project is mounting and wiring which brings up my question.

Splitter or dedicated antenna for the AIS?

I like the idea of having a backup VHF antenna mounted somewhere other than the masthead and using it for the AIS.

I also like the idea of simple. Wire in a splitter and you are done plus you get great range from the masthead antenna.

And the survey sez??

John
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Old 22-05-2006, 20:24   #5
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John,

Super Web page.. I just received a MUX because my old B&G repeater does not read the NMEA output of the Raymarine C80. Wout programmed it.. I will wire it up and take for a test drive this weekend.

Last weekend I installed the upgraded V3,18 software for the C series. Its a vast improvement in capabilities for the C80. The C80 now accepts AIS input and will display the data on the radar or the chart... or both.

I am NOT using a laptop and I am not very techie.. being more a plug and play electronics person. I do find the C series very awkward and not intuitive to use. Way to much focus on waypoints and routes... and reversing routes and creating routs from tracks and and moving waypoints and so on.

My approach has always been to program a few waypoints in advance ... even underway and set the auto pilot to one at a time and adjust the heading to compensate for the set of the current and leeway. I can't imagine a sailboat "following" a route... what with all the wind shifts, and sail trim required. All this waypoint "libraries" and routes are definitely aimed at the stinkpots and nerds who plan complex trips and sit at the top of the towers smoking cigars as the instruments drive them from dock to dock and hopefully all vessels move aside as they come. I know I usually AVOID power vessels at all cost.

The NASA AIS does seem like a good value for the safety it provides. I imagine in the not too distant future all vessels including yachts over say 30' will have AIS transmit capability at a reasonable cost and then things could get very clutter on your screen! Imagine sorting out all that data!

Which brings me back to standing watch and carefully observing the vessels and LIGHTS they are showing to know where they are going (or not). This means WATCHING from above deck and NOT a screen on an instrument in you Nav Station. Since I sail with myself or my wife, I can't be spending too much time playing with instruments below decks... and when I do..I have to pop up and scan the horizon FREQUENTLY to make sure everything IS okay... INCLUDING sail trim.

What I have found quite useful in my little Garmin IQue which is a palm device which has BlueCharts and is a WAAS receiver. All it displays is the ship's position, heading line, speed and coarse (SOG and COG)... no waypoints! This little chartplotter is often all I need to confirm what my eyes are telling me... or even remind me to look a bit harder to see something like a buoy which has not yet made its appearance.

As I don't sit behind the helm... the below decks auto pilot steers... I usually am positioned at the forward end of the cockpit under the dodger... where the instruments are arrayed in a "dash" console over the companionway. Keeps me out of the sun... and closer to the radar and plotter in the nav station which I CAN see from the companionway.

Until I got a chartplotter in '01 I ran my fixes on paper charts, transferred from a Loran at first and then a GPS. The two plotters I have are super... a Horizon CP170 an the C80. Offshore passages I always run a plot on paper with fixes ploted each hr.

Lately most of my sailing is in familair waters and navigation is mostly about collision avoidance than it is about figuring our where I am.

I rarely use the radar, except in the evening and in fog which is rare in Long Island... But the new MARPA feature looks interesting... and waypoints are usually "hazards" to keep to one side or the other... since getting there is tacking and gybing... Who ever sails a rhumb line these days? hahaha.

My thoughts...

Jef
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Old 22-05-2006, 20:26   #6
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I just started reviewing my old celestial notes and have ordered and received a new nautical almanac and HO 249 Vol 1. I guess great minds think alike and am glad someone else is looking back to the future (celestial). For other uses for the sextant I have a great recommendation: Shoreline and Sextant: Practical Coastline Navigation by John P. Budlong. The copy I have is published in '77 but there might be a newer version. Have done a couple of noon shots to get the old eye back in the right place and am having a ball. Regards, --John--
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Old 22-05-2006, 21:04   #7
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I found the VHF splitter to be very overpriced-nearly $100 for an automatic switch so you don't accidentally fry your AIS. And they do interrupt the AIS signal while transmitting. Splitters are not "simple" if you eliminate insertion loss, dangers to receiving elements when you transmit. Already had cabling for the redundant VHF antenna-plus liked the idea of the AIS horizon being about the same as the visible and radar horizons.
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Old 22-05-2006, 21:25   #8
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John,

Seems it took quite a while for Jack to get you over here… welcome.
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Old 23-05-2006, 01:39   #9
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Pure Vida - There was a piece in Lat 38 about Mexico wanting all cruisers to have an AIS transceiver (or something equivalent), but that seem to be a still-birth. However I would not be surprised if our protectors at Homeland Security don't pick it up and start running with it.
sded - I'm surprised you can pick up Navy vessels. While in Cascais I monitored a number of Portuguese and NATO warships on VHF, but they never showed up on AIS. In fact I once monitored a cargo ship in the Rio Tejo on the way to the Lisboa docks in conversation with an overtaking French warship. I could monitor both ship's VHF traffic as the warship passed the cargo ship. I also watched the AIS plotted progress of the cargo ship during this period, but no other ship showed up on the AIS plot. I just assumed military vessels do not broadcast on AIS. Maybe the U.S. Navy does in San Diego harbor then turns the transmitter off once out of U.S. waters.
Jemsea - although I used a dedicated VHF antenna on the mizzen, I'm looking to add a splitter to the antenna wire. It would allow me to easily use the AIS antenna and the main antenna as backups to each other. Right now the AIS antenna cable has a BNC connector for attachment to the NASA AIS engine so its either a splitter, BNC-PL259 adapter, or changing connectors when needed. I agree with sded that the splitters are way over priced for what they do. I'll just wait until the price comes down or make an adapter.

Jef - I agree, AIS plotting belongs on a display that can be seen in the cockpit. As soon as my repaired MUX gets here I will be wiring up a separate AIS (38,400 Baud) NMEA bus and connecting the C120 to it. I will likely continue to use the SOB AIS display on my PC as it is more robust than the current Raymarine implementation (although I've only used it in demo mode).
CaptainJeff - Yep, Jack drags in a lot of stray dogs. There goes the neighborhood I guess.

John
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Old 23-05-2006, 07:01   #10
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Jef,

You might call me a traditionalist, having first gone to sea when I was 16, when you talked to other ships with an Aldis lamp, when there was no Satnav not to mention GPS, when you went a week or two on DR in bad weather (good part was top speed was 10 knots), when the Raytheon or Decca radar was often down. You had to rely on the sun and the stars, occaisionally the moon and hope for a clear sky. Having said all this, I really appreciate the route function on my C80. I am seldom on the helm and with "route" and "track", the boat on autopilot goes to where I set it. It sure beats correcting all the time.

One traditional thing I stick to is keeping a good lookout. At night you have to know your navigation lights, when the sidelights disappear, when the stern light comes into view etc. This isn't too easy nowadays with cruise ships lit up like the Empire State Building. But keep a good lookout, day or night. That's the most important thing.

Which brings me to my favourite subject- "electronic idiots". Folks out there without any seamanship, piloting or navigation training running around thinking they're on Interstate 95. Last year, while at anchor in a fairly quiet anchorage I got hit end on by a large Irwin. When I boarded her I found out the reason. The helmsman was staring at a laptop in the corner of the cockpit rather than looking ahead. This was while he was coming out of an anchorage!

That's the one drawback on plotters. It's real easy to be fixated with them, looking at the screen rather than ahead and around especially when trying to get through tricky waters. The other drawback is they make you awful lazy (at least they do to me), not checking and putting my position on paper charts.
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Old 23-05-2006, 09:21   #11
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SkiprJohn - thanks for the note on the book. It looks like Amazon is gettinig some more of my money.
jstephens - the Latitude 38 article was where or row started. is seems that some felt that HS was the cause. And you do have an impressive sight.

How many folks that are using a sextant are using plastic vs metal? I'm using a Davis MK 15 and frankly have never depended on my sights to navigate. But my practice comes out close (how close is that shoreline anyway).
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Old 23-05-2006, 10:17   #12
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Rick,

Perhaps I was not clear about routes etc. I DO use waypoints...usually entered for leg of a journey. Typically, I don't need a series of them. For example on my recent sail from winter lay up to Shelter Island, where my summer mooring lies I did the following.

I left before mid day and visually navigated out of the marine, past the lift bridge... out a channel with 3 or 4 buoys marking the way to the sound. I used the autopilot once past the bridge and used the hands of the helm time to stow the fneders and the dock lines and hoist the sails. Winds were so light the motoring direction enabled me to set the sails with point to windward. I set each heading into the autopilot and confirmed it using the IQue to see that the COG was good keeping the boat in deep water.

Once out in the sounds past the buoys, I enter a waypoint 40 or so miles down the Sound at Port Jefferson. The course allowed us to sail there on a rhumb line if the wind permitted. There was little traffic, save for some saturday racing fleets and the occasional tug towing it's barge up or down the sound. I motor sailed and sailed the entire way, and used the time to do some cleaning and polishing on deck, misc little chores and preparing and eating lunch. I motored around the two races a sending me a bit to the south.

At the Prt Jef waypoint I hardened up and sailed visually through the breakwater. Here you have to watch for the Bridgeport ferries. They are big and move fast. Once inside I dropped the sailed and motored to the spot I anchored in. One waypoint entered for a 40 mile trip.

Next mooring I fueled up.. motored out raising the main before leaving the breakwater. Winds we light northerly so this was handy for making the exit while raising the main. Autopilot steered.

Once outside I set a waypoint for Plum Gut with enough "clearance" in the rhumb line to clear the headlands and some "reported rocks" around East Marion. This leg was about 50 miles and again motored and sailed the entire way. Hardly a vessel the whole time. I did pasta for lunch and finished cooking just as the wind filled in and the boat heeled to 15&#176;. This time I could see Plum Island and trimmed for speed and slowly turned the heading to the Light House.

ROunding the Light House in the Gut with current can set you a lot and it did... I motored out and tacked over and set one more waypoint which was the R2 off of Bug Light. I know the heading having sailed it 100 times...but I used the waypoint anyway. Here I had to watch for the Cross Sound Ferry and the occassional boats heading out to fish in the Gut.

From R2 it is all visual to the mooring, again I know the heading to the last buoy C7 which is 315&#176; from the R2.

I hardly even needed the waypoints. All they did was tell me how far I was, how far on or off the rhumb line and when I would be arriving at the waypoint. All the sailing was easily done visually or using a parallel rule on a chart of LIS to get the basic headings.

When sailing upwind to a waypoint entered in the GPS one CAN compute the optimum location to tack to fetch the mark... to minimize the number of tacks I suppose.

At night oine would have to be more observant of the compass as a the visual is much more ambigous in coastal sailing... and a DED reckoning is in order if you don't have a plotter... especially sailing around unlit shorelines.

How many waypoints do you use in a typical 8 or 10 hour cruise to a destinantion?

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Old 23-05-2006, 13:26   #13
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I apologize to all for not understanding a thing about what the discussion was supposed to centered on. Sounds like our old Navy system of IFF signalling (squeek.) Identify Friend or Foe. If you locked on to a target then they were obliged to identify themselves if they didn't want to get shot. Some of our targeting systems worked to well over 100 miles away so it was kind of required. Anyone know why it might be required on a recreational sail/powerboat?

Anyway, just to keep my 60+ year old brain alive I'm practicing celestial from shore. I do have a Capn Voyager program but have never used it. Maybe I'll use it when I do a bit more offshore stuff when the big boat gets back in the water.

Plastic (Davis) sextants are ok. Just have to be checked each time.

Regards, --John--
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Old 23-05-2006, 13:27   #14
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Quote:
How many waypoints do you use in a typical 8 or 10 hour cruise to a destinantion?
I try to use as few way points as possible. It's easier to sail in tight situatuaions if you don't put in any more than needed. The wind shifts and you need an extra tack or or you lose your intended course from a wind shift and need a reroute.

I find I can re adjust quicker and more accurately if I only plot the critical way points and let me navigate where I can sail. With most of my sailing on the Chesapeake there are mostly way points to help me clear the shoals and various points of land under and above the water. We have a lot of shallows here and they can be several miles out from shore. On a very long leg I might also plot another way point just to help track the distance and course to the mid mark. Crosing the soutern Bay I also plot a point on the Baltimore Channel in case large ships are close it's nice to have a better sense of exactly where the channel really is relative to your position ass judging distance isn't so relaible.

As far as a general number it depends. Going up a narrow channel off the Bay can be 9 miles and there may be 35 marks that desginate the channel I have to stay within or run aground. In that case I can easily be at 30 points.
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Old 23-05-2006, 13:50   #15
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I was originally far from convinced about the utility of an AIS receiver on a yacht. My last trip across the English Channel in a friends boat convinced me. I have to cross two very busy seperation lanes - a pretty fraught undertaking when you are only doing 5-6 kts. The AIS (+ Shipplotter software http://www.shipplotter.com) made this much easier and safer as we were alerted to any vessel with close CPA , and the system gave us these details even on ships 10 miles away, so appropriate action could be taken early.

I was so convinced that I have bought my own equipment and am fitting it
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