Chartplotter

[All U Get]

Hi all,
Knowing past discussions often bring out some strong feelings I would just like to relate what happened to us that could happen to some other sailors. We were sailing from Georgetown, SC to St. Mary's, Ga some 180 miles which of course included an overnight. It was cloudy making it totally dark except for the radar and chart plotter on low light and covered when we scanned all directions. Well just after midnight the chart plotter alarm blares and the "Missing heading data" scrolls on top of the screen. The warning says to hit the menu button, that only confirms the alarm went off.
We shut down the system and restarted with no change. Then another alarm with "Position data missing" The screen changed to 0 00 000 Lat. and 0 00 000 Long. Radar, second GPS unit, and autopilot were still working so we maintained our course and extended our radar range. The clouds moved off and a crescent moon lit half the ocean to our stern.
We fell back on our Dead Reckoning skills plotting a point every hour on our paper charts. As the wind eased we were able to adjust our course to pass by lit and unlit obstacles through the night.
After nearly 6 hours we got a nice sunrise and a view of an empty ocean all around. I rechecked my math many times to assure my wife and myself that we would see something/anything on the horizon. When we finally saw a buoy ahead we passed close enough to confirm our position then readjust the autopilot again. By 9 am we could see the travel lane for St. Mary's. We made it up the river to R34 where we turned to the side to get to the anchorage 2 miles further.
We had a general idea of the shape of the land from the paper charts so without any navigational aides we crept in using approximate times and the depth finder. It was a little difficult because the SOG wouldn't work without GPS positioning. We made the slow curved turn along Cumberland Island to anchor among the other boats. Without the DR skills and paper charts, well its a big pond.
Currently we've moved on by following friends and building a chart plotter with my laptop, only ran aground once.

All U Get

 

[capta]

I have moved my GPS antenna from the stern rail to the coaming just forward of the main companionway hatch. It has greatly reduced the radical swinging heading line and it is much more protected from harm, and actually increased performance. I've wanted to try this for years, but had some trepidation that the bimini bars and closer proximity to the main mast and boom might hinder performance.
As the Garmin antenna has a connector on it and we carry a spare, it might take 20 minutes to change it out, without hanging over the pushpit to do so.
Just a thought if you find you need to replace the antenna. An interesting aside; The actual GPS unit on some Garmin chartplotters is in the remote antenna, not the chartplotter. This makes it a good idea to carry a spare.

 

[dlochner]

A good story to support traditional navigation and piloting skills. Glad you were able to find your way in.

It is also an argument for redundancy. At last count we're up to about 8 gps enabled devices: a couple of iPhones and iPads, a chart plotter, a couple of handheld gps's and a gps/ais receiver built into the vhf. Any of those devices can give us a position fix that we can plot on a paper chart.

 

[Kings Gambit]

AUG--thank's for your account of how to deal with the unexpected partial loss of navigation. You're now in the best condition to answer the question posed in a thread of this past summer, which you've already done, but perhaps post it there as well?

KG

http://forums.sailboatowners.com/index.php?threads/when-your-gps-fails-how-do-you-navigate.170935/

 

[Gunni]

Plan A - mounted MFD chartplotter (antennae 1)
Plan B - old Raymarine chartplotter at the nav station (antennae 2)
Plan C - Garmin battery powered 640 GPSmap. (built in antenna)
Plan D - Garmin GPS 76Map handheld (built in antenna)
Plan FUBAR - Garmin 88 handheld in the ditch bag

 

[Kings Gambit]

Plan A - mounted MFD chartplotter (antennae 1)
Plan B - old Raymarine chartplotter at the nav station (antennae 2)
Plan C - Garmin battery powered 640 GPSmap. (built in antenna)
Plan D - Garmin GPS 76Map handheld (built in antenna)
Plan FUBAR - Garmin 88 handheld in the ditch bag

So, the government shuts off the GPS satellites in a national defense situation when you're half way to Bermuda. Then what?

 

[dlochner]

Well, if you have been keeping a decent log updated on the hour and you know your compass heading and speed, then you just dead reckon your way to where ever.

 

[Meriachee]

Then what?

Keep an eye out for 5 Avengers? (Sorry, I couldn't resist)

 

[Gunni]

That actually happened to us near Balt'more during Desert Storm. Offshore we plot positions and course on the paper chart. But Bermuda is a small target and an expensive port, so good news crew, liberal leave somewhere in South Carolina!

 

[Kings Gambit]

Well, if you have been keeping a decent log updated on the hour and you know your compass heading and speed, then you just dead reckon your way to where ever.

I think I'd trust the "Admiral of the Ocean Sea" to hit Bermuda using DR from 300+ n.mi. out; I don't know about the everyday recreational sailor. I admit that I do not carry a sextant and sight reduction tables aboard, nor SSB or HAM radios, nor SAT phone. I guess if I were going to Bermuda (or HI from this coast), I should/would be so equipped the way things are going these days.

 

[Joe]

Tania Aebi sailed by herself from New York to Bermuda with nothing but a Radio Direction Finder, a magnetic compass and an instruction book.

 

[Kings Gambit]

Tania Aebi sailed by herself from New York to Bermuda with nothing but a Radio Direction Finder, a magnetic compass and an instruction book.

Yeah--but just barely found the island/harbor as I remember--I read the book too! Besides, I'm curious--are there still RDFs in operation out there? And who carries one?

 

[shemandr]

We used to have one on my Dad's boat. I was young but I remember a lot of colorful language. Yet we always got where we were going - Block Island - not Bermuda. I don't know if they are still active. There's something nostalgic about hearing those beeps. I could never understand the "Null" thing. I always thought the instrument should point at the beacon. Like I said, I was young.
After one foggy trip he bought a "Marinized" loran. Big upgrade! We could plot our position on a chart with accuracy. Every one of 4 kids on our boat could do it faster than the adults. Good memories.

 

[All U Get]

AUG--thank's for your account of how to deal with the unexpected partial loss of navigation. You're now in the best condition to answer the question posed in a thread of this past summer, which you've already done, but perhaps post it there as well?

KG

http://forums.sailboatowners.com/index.php?threads/when-your-gps-fails-how-do-you-navigate.170935/

Maybe that's why the DR skills were rattling around in my head, must have read your thread. I really don't have an original thought, the little voices tell me what to do.

All U Get

 

[All U Get]

Just read Joshua Slocum's book Sailing Alone Around the World. Good read, I'm sure I'll remember his exploits when I need some insight.

All U Get

 

[All U Get]

Keep an eye out for 5 Avengers? (Sorry, I couldn't resist)

Or Crichton's 5 Deaths.
All U Get

 

[Kings Gambit]

We used to have one on my Dad's boat. I was young but I remember a lot of colorful language. Yet we always got where we were going - Block Island - not Bermuda. I don't know if they are still active. There's something nostalgic about hearing those beeps. I could never understand the "Null" thing. I always thought the instrument should point at the beacon. Like I said, I was young.
After one foggy trip he bought a "Marinized" loran. Big upgrade! We could plot our position on a chart with accuracy. Every one of 4 kids on our boat could do it faster than the adults. Good memories.

I've mentally relegated RDFs to the same heap of obsolesence as Loran C and marine operators. My very first (celestial) navigation course was in 1975 or '76 in San Diego from the USPS, b/f I even owned a sailboat; when RDFs, Loran C, marine operators, and sextants were what many, if not all, mariners relied on at some point. I can still "hear": "This is the San Diego Marine Operator calling the vessel ...!" This was when Kettenburg still had a store on Shelter Island, Kettenburg Marine.

 

[heritage]

The aural null of the old RDFs occurred when the units directional antenna was turned so that no signal was received from the broadcasting station. As you manually turned the antenna (some of the later RDFs became ADFs and automatically turned to the aural null) and listened for the signal to disappear, one could determine within 10 degrees or so the relative direction of the station. Any strong AM station would work as long as you could determine its location. Bermuda should be easy,,, with the British accents. You could do the same thing today with a portable radio with a bar type antenna on the AM setting.

 

[Joe]

Yeah--but just barely found the island/harbor as I remember--I read the book too! Besides, I'm curious--are there still RDFs in operation out there? And who carries one?

Like I said, she had the instruction book with her.... but didn't start reading it till she lost her DR position in a storm.... so she went around in circles till she could figure the thing out...quite a character.

As long as there are radio stations broadcasting and people using vhf or similar straight line transmitters, the RDF is still useful. So.... if your govt gps satellite shutdown scenario should occur.....you got that going for you. https://en.wikipedia.org/wiki/Radio_direction_finder

 

[Kings Gambit]

Like I said, she had the instruction book with her.... but didn't start reading it till she lost her DR position in a storm.... so she went around in circles till she could figure the thing out...quite a character.

As long as there are radio stations broadcasting and people using vhf or similar straight line transmitters, the RDF is still useful. So.... if your govt gps satellite shutdown scenario should occur.....you got that going for you. https://en.wikipedia.org/wiki/Radio_direction_finder

I found this at your link: "Today many NDBs [non-directional beacons] have been decommissioned in favor of faster and far more accurate GPS navigational systems. However the low cost of ADF and RDF systems, and the continued existence of AM broadcast stations (as well as navigational beacons in countries outside North America) has allowed these devices to continue to function, primarily for use in small boats, as an adjunct or backup to GPS."

Also, the range is limited; operationally, on a small boat, you'd already have to be w/in probably 25 to 50 n.mi. of a transmitter. Good enough, perhaps, to prevent a "near miss."