How do you use your chart plotter?

[jonjo]

I tend to be a seat of my pants navigator who would never pass an RYA exam. As a result I sometimes wander into danger but have an instinct for recognizing danger and digging myself out of such a situation.

Having read posts in the other plotter thread it occurs to me that I do not use mine the same way e.g. sail between waypoints researched before departure, instead I head off on a passage with a belief that I know how to get from A to B using the English Channel chart lodged in my brain. The plotter is just there for reassurance.

For example if heading to St Peter Port from Gosport this is how I would navigate:

1. With zero preparation leave when I am ready probably sometime in the afternoon with an expectation of a night at sea.
2. Through prior observation I will have an idea of when I will not have to punch the tide at the Portsmouth harbour entrance.
3. Once outside the harbour entrance while at the helm I will zoom to a tidal diamond near Yarmouth to see when the Hurst tide turns east and do a quick mental calculation to see if I can scoot down the Solent before the tide turns, if not I will head out east around the IOW.
4. Mental pilotage will get me to Ventnor, I might sneak a view at the plotter screen to be reminded of offlying dangers near Culver Cliff.
5. From memory I know I can scrape past Ventnor fairly close.

And now onto the crossing.

1. I will steer for a middling point in the Race after scrolling the plotter to the Race.
2. After observing boat speed I will estimate time to the Race in my head.
3. I will then find a tidal diamond on the screen 10 miles north of Cap De La Hague and estimate east/west offset by totting up the net offset for the final 3 hours approaching the Race.
4. Mentally plotting that offset on the screen I will then adjust the helm to head for that point by watching the plotter course prediction line move on the chart zoomed to the Race.

Job done, enable the autopilot and time to open a beer.

Six hours later I will repeat the last 4 steps above minus the beer.

 

[capnsensible]

Jolly good. Would probably do much the same (but leave earlier and no beer!)

Question. What happens when someone puts their knee through the screen or bashes the screen with a winch handle,or breaks off the gps ariel whilst using it as a handhold when vomming? Considering also that smarty phones haven't always been there and not all boats carry a spare gps and spare batteries....

Having coped with those and more, I am comfortable with my chart and compass navigation too because Ive had to. Plotters are great, in my opinion, but, well, there is always a but!

 

[Angele]

For example if heading to St Peter Port from Gosport this is how I would navigate:

1. With zero preparation leave when I am ready probably sometime in the afternoon with an expectation of a night at sea.
2. [snip]

So, on a passage that will take you through the Alderney Race, your departure time is set completely ignoring the tidal conditions you can expect based on your likely arrival time???

If I'm hoping to go south of Alderney, then my departure time is selected based on my knowledge of likely passage time at least a couple of days ahead, and then updated based on weather forecasts in the 24 hours leading up to my departure (in this example to arrive off Cap de la Hague at HW Dover).

In practice, since I like to sail in daylight and I time my arrival in time for dinner at my destination, the tide conditions will often dictate which week I select for a trip like that.

I use the electronic ruler on my chart plotter to measure the (10ish hour) tide vector from my waypoint on the other side (e.g. midway between Cap de la Hague and the tip of Alderney) in order to determine my course to steer, updated again when halfway and 3/4 across (unless passage speed differs materially from what I was expecting, when I will do the recalculation earlier).

My position is noted in the log hourly, in case I need to transfer it onto the paper chart if the electronics were to fail.

 

[jonjo]

Question. What happens when someone puts their knee through the screen or bashes the screen with a winch handle,or breaks off the gps ariel whilst using it as a handhold when vomming? Considering also that smarty phones haven't always been there and not all boats carry a spare gps and spare batteries....

No performance wobbles from the plotter in 6 years of use.

As it happens I do have a second basic hand held GPS and so could transfer a position to a paper chart.

In the event of complete electrical breakdown I reckon I could find my way back to an English port with a compass, echo sounder and eyeballs and knowledge of coast topology plus rock geology.

 

[capnsensible]

Good, I reckon practicing with your back up now and then is a good idea too.

 

[johnalison]

Crossing the English Channel is such a navigational doddle that a plotter is hardly necessary, though a GPS is a great boon. Where a plotter comes in is during a more complex passage, such as we often find when sailing along a coast and between islands. Here, the ability to enter a complicated route quickly and display your position in an effective way makes a plotter a pleasure to use, though hardly essential.

I use a plotter as a generator of routes for most passages, for reassurance to my wife, and to coordinate my chart, AIS and radar displays.

 

[jonjo]

So, on a passage that will take you through the Alderney Race, your departure time is set completely ignoring the tidal conditions you can expect based on your likely arrival time???

Yes. In practice if I was out by a full tidal phase then I would duck into Bray Harbour.

If I'm hoping to go south of Alderney, then my departure time is selected based on my knowledge of likely passage time at least a couple of days ahead, and then updated based on weather forecasts in the 24 hours leading up to my departure (in this example to arrive off Cap de la Hague at HW Dover).

In practice, since I like to sail in daylight and I time my arrival in time for dinner at my destination, the tide conditions will often dictate which week I select for a trip like that.

Hmm this makes a lot of assumptions about weather, where to go is better dictated by wind direction anticipated a day or day earlier.

I feel sailing to a schedule and trying to anticipate a tidal gate 14 hours ahead leads to more motor sailing. Your approach will sometimes knock say 3 hours off a 14 hour passage when it all comes together but if half a night of sleep is lost to achieve that I am not sure it is worth it.

When single handing I always try to avoid a second night at sea, so prefer to set off knowing I am fully tanked up with sleep and able to cope with 1 full night at sea.

 

[Tintin]

The problem I find with just using plotters for solo sailing pilotage, is that it can take several clicks to find a lights characteristics, which at night in places like Chenal de Four or even Poole Harbour in a blow, means that the seat of the pants approach leaves you seriously exposed to getting it badly wrong 'cos your head is buried in a screen when in fact you should be using no 1 eyeball and paper pilotage scribbles.

Since a nasty 10 minutes last year in the Chenal at night when I thought I could get away with just the plotter in waters I knew, I now religiously have a paper pilotage plan with lights and characteristics marked clearly, and use the plotter for general heading guidance.

 

[LadyInBed]

Jonjo, how you describe your seat of pants navigaton wouldn't work for me, plotter or not.

 

[dom]

Yes. In practice if I was out by a full tidal phase then I would duck into Bray Harbour.

Personally I wouldn't do it that way, Braye can seem very far away should you accidentally find yourself downwind and downtide of the island, even by ten or so miles to the NE. And that's not to mention the directionally restrictive TSSs should you find yourself approaching from the NW

Toss into the equation that the prevailing winds are from the SW and I'd have thought it was time for a few half decent vector calculations. Thy're really easy even without fancy electronic gear given the many free apps and programs on the internet, e.g:
http://www.1728.org/vectors.htm.

Just ignore the fact that mathematical angles are denoted as starting from due East as opposed to North so to speak. Simply use your Tidal Atlas to estimate the cardinal direction and speed of the tide along your expected route. Bang them along with your expected boat speed into the vector calculator and Bob's your uncle, and an accurate chap he'll be at that!

 

[nicho]

All this is fine, but sailing around the myriad of rocks of the Channel Islands with no chartplotter if/when serious mist/fog or poor visibility turns up unexpectedly is......well, extremely dodgy in my opinion (and these conditions are not always forecast). I really do not see the problems some of you have with chartplotters - by all means rely on your own skills, it can be very rewarding, but crossing the channel on a night passage if hit by poor viz in the main shipping lanes without plotter, and more importantly radar, is not a good idea surely? I'm sure all you Marco Polo's will shoot me down, but in my boating, as well as my flying, I consider electronic wizardry a must when conditions deteriorate below forecast levels, even if they are left on standby much of the time.

 

[Angele]

Hmm this makes a lot of assumptions about weather, where to go is better dictated by wind direction anticipated a day or day earlier.

I feel sailing to a schedule and trying to anticipate a tidal gate 14 hours ahead leads to more motor sailing. Your approach will sometimes knock say 3 hours off a 14 hour passage when it all comes together but if half a night of sleep is lost to achieve that I am not sure it is worth it.

When single handing I always try to avoid a second night at sea, so prefer to set off knowing I am fully tanked up with sleep and able to cope with 1 full night at sea.

With a range of weather models available, I'll have a pretty good idea a day in advance if my passage plan is likely to be deliverable. If it isn't, it is likely to be either: beating to windward, so I'll probably change my destination, or too much wind, in which case I'll confine myself to sheltered waters. You are correct, though, I do end up motoring across for quite a few of my Channel crossings if not enough wind. I arrange crew weeks (or even months) in advance, so I can't easily delay a trip for a few days until the wind is more suitable, and I find getting crew is easier if you say "the plan is to go to [xyz] (subject to weather)", rather than "well we'll see which way the wind is blowing on the day."

I do like to have a plan, but the chart plotter isn't a passage planning tool for me. On cross-Channel trips I do like to observe the s-curve of where I have been and I'll put the destination in as a waypoint so I can give the crew a countdown ("only 30 nm to go chaps; we should be there around G&T O'clock"). For me the plotter is really more of a tool for pilotage in unfamiliar waters, with some useful tools (like visual access to tidal curves).

 

[dom]

...but in my boating, as well as my flying, I consider electronic wizardry a must when conditions deteriorate below forecast levels, even if they are left on standby much of the time.

You mean you rely on electronic wizardry in IMC conditions. Tut tut, you'll have made Wilbur and Orville Wright turn in their graves!

 

[capnsensible]

All this is fine, but sailing around the myriad of rocks of the Channel Islands with no chartplotter if/when serious mist/fog or poor visibility turns up unexpectedly is......well, extremely dodgy in my opinion (and these conditions are not always forecast). I really do not see the problems some of you have with chartplotters - by all means rely on your own skills, it can be very rewarding, but crossing the channel on a night passage if hit by poor viz in the main shipping lanes without plotter, and more importantly radar, is not a good idea surely? I'm sure all you Marco Polo's will shoot me down, but in my boating, as well as my flying, I consider electronic wizardry a must when conditions deteriorate below forecast levels, even if they are left on standby much of the time.

Worth remembering that some people sailed around the Channel and the Islands before plotters were invented!. We coped....

 

[RupertW]

All this is fine, but sailing around the myriad of rocks of the Channel Islands with no chartplotter if/when serious mist/fog or poor visibility turns up unexpectedly is......well, extremely dodgy in my opinion (and these conditions are not always forecast). I really do not see the problems some of you have with chartplotters - by all means rely on your own skills, it can be very rewarding, but crossing the channel on a night passage if hit by poor viz in the main shipping lanes without plotter, and more importantly radar, is not a good idea surely? I'm sure all you Marco Polo's will shoot me down, but in my boating, as well as my flying, I consider electronic wizardry a must when conditions deteriorate below forecast levels, even if they are left on standby much of the time.

And this sort of post is why us Marco Polo's despair. A plotter can make an awkward task a hell of a lot easier but I can think of nothing simpler than a night channel passage. Radar would certainly help in shipping lanes, a phone GPS would be great in poor vis but a plotter adds little that is necessary. Very nice, though.

In fixed rocky channels in waters with charts that accurately match GPS positions a plotter can certainly be very reassuring but the CIs have some of the biggest and best fixed markers of anywhere in the world. Hard to get lost there except in vis so poor I would not go into a narrow channel for fear of hitting somebody coming the other way.

 

[fastjedi]

Crossing the channel ....
- We fill in the channel tidal atlas so we know which way the tide is going at any given time
- Based on the wind forecast I make a subjective call on how much more or less that 2 tides we will take
- This (+ being up tide of the destination) tells us if we need to head slightly higher of lower than the compass direction
- We plot our position on the chart every two hours from the DSC radio display and makes a call on our position vs lay line
- I find the chart plotter ruins the experience on a crossing

However,
- I might switch the chart plotter on if we are in doubt when approaching the destination
- We would have the plotter on sailing through CI rocks
- We were also using tide directions from Navionics / Nexus 7 on the crossing this year - Very impressed!

 

[johnalison]

The CIs seem to have more than their fair share of fog, butthat's another matter. The chief use of a plotter on a straighforward passage such as the Channel for us is simply to save time below at the chart table, the most likely cause of seasickness with us. Having a plot of one's position is nice too, and the display can be very graphic: sorry about the quality:

 

[prv]

I don't really use the plotter at all while crossing the Channel. Either turned off, or possibly in full radar mode. I'll have sketched our likely ground track (C or S curve) on the chart based on the tide vectors, and then compare the hourly plots to that.

Pete

 

[Bru]

I use my chart plotter in, fundamentally, exactly the same way I would use a paper chart

I do my passage planning either on paper or (for more complex passages particularly vis tides) on the laptop anyway

The route I intend to follow and key waypoints are entered into / transferred to the plotter

Under way, I know where I am, where I should be and where I'm gong on in relation to the chart at a glance

I could take fixes, plot them and plot DR positions etc on a paper chart of course. I would then have a significantly less accurate idea of where I am and where I'm going!

I don't religiously follow the line on the screen, that would be silly when sailing. I sail to best advantage

I do find some of the computed information useful (the ability to obtain accurate real time set and drift info, VMG to wind or waypoint and ETA at current SOG to next waypoint and destination to name but a few). Of course, one could work it out by hand and one could manage well enough without but it all adds to the overall picture in my head of

I do find it frustrating that none of the plotters or PC navigation packages have the (not hard to programme I reckon) facility to draw tidal vectors on screen. On the rare occasions it might matter I'd draw it up on paper (plain even, it doesn't have to be drawn on a chart)

I will however admit that I am not a fan of Navionics charts (our plotter is a Raymarine) and I often fall back on the Memory Map app and my full set of Admiralty raster charts when I want to see the bigger picture (on both my smart phone and the laptop)

So anyway I struggle to understand the hangups some people seem to have about chart plotters. They're a tool to aid navigation. There are pros and cons and you have to be aware of that but even a small screen plotter is a lot easier to use than faffing about with paper charts especially on a small boat in rough conditions

 

[Pinnacle]

Which one are you referring to?