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Old 17-02-2016, 00:19   #31
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Re: Paper chart v Plotter

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Originally Posted by CapnBazza View Post
Oops, is that 5" a diagonal of the screen?
that is what Mike is going to find out once he found his gizmo
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Old 17-02-2016, 01:19   #32
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Re: Paper chart v Plotter

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that is what Mike is going to find out once he found his gizmo
Have the gizmo in my hand now.

It is a Lowrance LMS 480

Incidentally it is not loaded with any cartography at all, I just use it for fishing wrecks.

I have lots of wrecks stored on SD cards? (about the size of your thumb nail) and load them depending where I am.

It is 5 inch diagonal.

I am also wrong about its level of ZOOM.

Someone might be able to check this online but I think it is a dual purpose terrestrial/marine type of gizmo and I am not sure that there is an option to use nautical miles.

I have not got it switched on so unable to check.

I think it gives the choice of statute miles or Km.

You will be able to comprehend when fishing tiny wrecks and bits of scrap to have lots of ZOOM is a big advantage. The ZOOM goes to 0.03 which if the set is set to Km gives 30m not 20m as my failing memory advised me yesterday!

If set to statute miles 0.03 would give 17.6 yards x 3 = 52.8 yards. Not really sure what this means but the gizmo is an amazing piece of kit for what I do with it.

So if anyone still has any enthusiasm based on the revised ZOOM figures how big would my chart table need to be?

The chart I happen to have to hand is 53M N to S and +/- 35M E to W


Mike
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Old 17-02-2016, 01:22   #33
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Re: Paper chart v Plotter

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Originally Posted by grantmc View Post
So what do you think chart plotters base their display on if not from those same surveys? In essence the same chart that was produced (in the largest scale for the area in question) from the last survey with notices to mariners applied, forms the basis of the chart plotter's data base?

Relying on a display after zooming in isn't necessarily a good idea. You need to be cognisant of the scale of the base chart from which the plotter is doing its display. The chart plotter display can be no more accurate than the largest scale chart.
Been wondering why you would reiterate what I thought I had just made clear but the penny has finally dropped. Life gets tough when you are getting hard of thinking.

Mike
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Old 17-02-2016, 01:30   #34
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Re: Paper chart v Plotter

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Sound advice Grantmc. Good thing Mike's not using old Loran charts in microseconds.
Decca is what I used to use in the 80's & 90's Chain 2a and 3b Red Green & Purple I seem to remember.

Then GPS was introduced 1,500 for a GPS set which was completely useless, Decca was streets ahead.

Then I became aware of DGPS so a new little black box was purchased for 1,000 with a 1,500 annual subscription.

By now I was 4,000 poorer but did have a navigation system that was as good as DECCA. Oh and I already had DECCA!

Mike
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Old 17-02-2016, 02:23   #35
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Re: Paper chart v Plotter

with the revised numbers (30m and 5''diag, using barnakiels display height calculation):
30/0.0567 = 529.1 : 1
53nm chart at that scale would be 0.10017 nm or 185.5m

is that 35nm EtoW or arc minutes? at witch latitude?
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Old 17-02-2016, 03:02   #36
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Re: Paper chart v Plotter

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with the revised numbers (30m and 5''diag, using barnakiels display height calculation):
30/0.0567 = 529.1 : 1
53nm chart at that scale would be 0.10017 nm or 185.5m

is that 35nm EtoW or arc minutes? at witch latitude?
Hi Simon,

You are right to ask. It is the full width of the navigational portion of the chart measured E to W (approx 18 inches) then measured on the latitude scale.

Therefore I guess latitude is not an issue?

Mike
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Old 17-02-2016, 03:18   #37
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Re: Paper chart v Plotter

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Hi Simon,

You are right to ask. It is the full width of the navigational portion of the chart measured E to W (approx 18 inches) then measured on the latitude scale.

Therefore I guess latitude is not an issue?

Mike
correct
the chart table needs to be 122.5m wide than.
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Old 17-02-2016, 03:30   #38
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Re: Paper chart v Plotter

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correct
the chart table needs to be 122.5m wide than.
Thank you,

Mike
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Old 17-02-2016, 03:57   #39
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Re: Paper chart v Plotter

Rather than wreck my paper charts (my handwriting is so bad, some have suggested I should have been a doctor, and even I can't read it sometimes), I used to use tracing paper and a pad of very large graph paper (A3).

Transferring the outline of where I wanted to travel, along with essential points, to the graph paper, didn't take long, and the grid of the graph paper was really handy for plotting DR positions on (generally I used RDF and a hand bearing compass, if my 5+ mile accuracy with a sextant wasn't good enough - definitely not close to shore), though in my case as I had used graph paper a lot in all manner of ways, perhaps I was just more comfortable with it.

In fact a big pad of graph paper is going to be my 'Chart' across the Atlantic (as there's not exactly much in the way of fixed objects to bump into). A longitude a safe distance offshore West (where normal charts end) at one side, and a longitude a safe distance offshore East (where normal charts start) on the other, then plot latitude departure point and latitude arrival point, then the fixes in between. Then I can scribble all sorts of notes on it as I do my log (things like don't head off this way, there be dragons). If it fills up with my illegible scribbles, I can rip the top sheet off and do another one.

I do like the thought of electronic charts I must admit, and as I was always aware of the very real inaccuracies with paper ones, as long as you are aware and exercise due caution, you 'should' be able to get along ok, and perhaps better, with the electronic ones.

I am very aware of not having too big a display in the cockpit though. The trouble with computer screens is, they can easily be very hypnotic and distracting, and can take your eye off the ball as a result. eta: In fact you have to question the sanity of putting games on a cockpit display, and even things like being able to select music to play, play lists, and other such irrelevant nonsense. You can't exactly tell an oil tanker bearing down on you to hang on for a bit, as you have to finish this level?

So for me it's laptop down below (OpenCPN - with USA and UK Admiralty 'For Navigation' charts), and a 4" Dragonfly with Navionics charts on the binnacle. With NOTHING 'networked'.

Too easy and too convenient, all too often leads to too lazy and too unaware of what's actually going on, and that frankly, is way too dangerous a place to even think of going to. When even pilots are crashing planes because the display screens are holding their attention, to me it's way past time for a rethink.
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