Navigation Systems, single screen vs multiple displays and redundancy

[wrr]

Lockdown at least provides the opportunity to review electronic systems etc., albeit from afar. Currently, I have separate wind, GPS, AIS and depth/log displays, with two GPS instruments, one active/passive and one passive only AIS, linked VHF, NMEA 0813 and 2000 connections, two depth transducers and, of course, paper charts. This cheerful jumble of independently circuited electronics does provide a margin of safety due to redundancy, although the integration of information is in one's head rather than on a single screen.
While a single display might be more elegant, I am concerned about the vulnerability of a single display system to failure, leading to loss of the information from every input at once. Is this the intrinsic bias of a luddite or a genuine concern about margins of safety?

 

[scruff]

Are you sure you only have 2 GPS's aboard?

Between my wife & I, we have 2 GPS enabled watches,
My personal phone, work phone & wife's phone,
Tablet
chart plotter
gps at chart table.

So that's 8, independent devices capable of doing required navigation before any crew step aboard.

I'd be quite happy moving over to a modern MFD with the level of backup we carry day to day

 

[[70521]]

Don't forget your sextant, tables and plotting sheets.

 

[Stemar]

I can see advantages to having duplicate displays at the helm and the nav station, but I'm with scruff. I haven't got a fixed plotter, but we almost always have three GPSs aboard.

 

[Deleted member 36384]

What is critical to the safety of your boat, in the context of instruments? I suggest that it is only the plotter. If you have an independent back up to the plotter then don’t worry about loss of it.
The back up could be another device e.g. smart phone, or a set of charts.
I would not worry about it as you have paper charts as backup.

 

[greeny]

Lockdown at least provides the opportunity to review electronic systems etc., albeit from afar. Currently, I have separate wind, GPS, AIS and depth/log displays, with two GPS instruments, one active/passive and one passive only AIS, linked VHF, NMEA 0813 and 2000 connections, two depth transducers and, of course, paper charts. This cheerful jumble of independently circuited electronics does provide a margin of safety due to redundancy, although the integration of information is in one's head rather than on a single screen.
While a single display might be more elegant, I am concerned about the vulnerability of a single display system to failure, leading to loss of the information from every input at once. Is this the intrinsic bias of a luddite or a genuine concern about margins of safety?

That depends on the confidence you have in your ability to navigate safely without it. Charts, compass and navigational skills worked for a long time before GPS or Decca came along.

 

[Kukri]

Spotting a ‘new’ multi function plotter, identical to the one over the chart table, on eBay at about half price, I snaffled it intending to have one at the helm as well. I wanted two identical units. That was my last thing on the to do list before lockdown.

I now feel downright decadent as I can see the chart table one from my bunk.

Yes, we too have hot and cold running GPS receivers and aerials.

 

[lw395]

What is critical to the safety of your boat, in the context of instruments? I suggest that it is only the plotter. If you have an independent back up to the plotter then don’t worry about loss of it.
The back up could be another device e.g. smart phone, or a set of charts.
I would not worry about it as you have paper charts as backup.

Personally, I would say the depth sounder can be more crucial to the short term safety of the boat.

When electronics start going wrong, it's not good if a single failure prevents every thing from working.
GPS is not always accurate enough to tell you that you've left the channel. Channels can shift after a storm.
Water under the keel is real, immediate and doesn't need a graphic display.

A compass can also be pretty crucial.

Paper charts as back up is fine, but a chart on its own isn't much help, you need to fix, check and monitor your position on that chart.
What scenario is it supposed to be insurance against? Failure of the plotter? Absence of a GPS transmission? Error in the electronic chart data?

 

[Iliade]

I would be more concerned about the replacement cost than the immediate need.

The trouble with multiple instruments is that the chance of something going wrong increases almost linearly with the addition of each extra unit, but each cost event is smaller.

 

[Porthandbuoy]

Don't forget your sextant, tables and plotting sheets.

I don’t, it’s part of the fun.

Electronically I use a netbook running OpenCPN with a spare in the chart table. But with phone, iPad and a handheld GPS on board as well there’s no excuse for getting ‘lost’.

 

[James_Calvert]

I am concerned that you have a combined depth and log display.

I was happy to go without a log whilst it was away for repair.

I wouldn't have been very happy without depth information, mind you we were based in the Medway at the time.

 

[Stemar]

It could come in handy in the Solent, too

 

[oldmanofthehills]

I like redundancy - but then I work in safety critical industry. My solution is to have radio with built in GPS plus AIS. Plotter with own GPS and Depth guage. If plotter fails GPS on radio means easy use of chart. Nav App on phone as an assist.

I have separate depth gauge as part of tac tic system though cant be used at same time as plotter or it triples depth. As a creek crawler I might have installed a back up depth guage if previous owner had not installed tac tic, but i have a 5m lead line and thats good enough for our as yet unsold other boat

There is mechanical log and a log on the tac tic system. Neither is reliable and their only use was to confirm that gearbox clutch was gone as could only do 1.5kts at full revs. It might be more useful to a racer but I only care about speed over the ground

 

[prv]

What is critical to the safety of your boat, in the context of instruments? I suggest that it is only the plotter.

Inshore, it’s losing the depth sounder that would really concern me, over anything else.

Offshore, a GPS receiver takes that place (though it doesn’t have to be a plotter).

In thick fog, add radar to either of those.

These are the things I’d be genuinely uncomfortable without, rather than merely inconvenienced. Not coincidentally, all three of them tell you things you can’t directly detect with your own senses.

Pete

 

[wrr]

Many thanks for the collective wisdom. We are delightfully free of smartphones at sea. Having experienced a fellow rail traveller (in pre-Covid days) drop my laptop and break the motherboard and having lost hard disc functionality in two other laptops, I would be reluctant to depend on a single multiple-function device. To my mind, replacement of the multiple display heads will require two autonomous MFDs, one in the cockpit and one at the chart table, since otherwise all electronic data (log, depth, GPS, AIS) could be lost with a single glitch/failure. Given the potential costs, including NMEA 0813/2000 converters, I think that this upgrade may have to await the failure of one of the current systems!

 

[Boathook]

When I renewed my instruments a few years ago I upgraded to a mfd and separate depth, speed, wind instruments. Being raymarine all the data comes from a single point (itc-5 unit). Both sets can work separately and I could always alter the wiring for data to go straight to the separate instruments if I had failure of the ITC-5. Radar and ais are both standalone but the ais requires the mfd to show plots. The mfd is a wonderful bit of kit imho.