GPS

[AntarcticPilot]

[QUOTE=NDG;2304577]

Originally Posted by AntarcticPilot

Latitude doesn't even need the time-source.

QUOTE]


Is that correct? Its a long time since I learnt a bit of astro-nav, but I thought a sight for lat needed to be done at midday (or some other known time)?

Could be wrong.

You determine Midday by observing the maximum elevation of the Sun, and of course the Sun is due north or south at midday. You can anticipate when to start observing by using very crude time-keeping (they used sand-glasses in the sailing navy days!).

Then it is just a matter of very simple addition and subtraction to get latitude.

Alternatively you can get latitude at night by observing Polaris; although Polaris isn't quite at the celestial pole, it is near enough for the accuracy of observation from a small vessel.

Once you have latitude, you can use the time-honoured technique of "running down the latitude"!

And I doubt if there is a reliable method of ensuring power supply on a sailing vessel, short of installing a nuclear thermo-electric generator. Anything with moving parts can fail from mechanical causes, or by stress of wind and sea. And electricity and salt-water don't mix, in exciting and interesting ways. Sailing boats present a perennially damp and salty environment, even on a marina berth!

DR on a sailing vessel can rapidly accumulate errors that make it only slightly better than sticking a pin in the map while blind-fold.

[asteven221]

Personally - electronics any day! Paper charts? Got them but have not used them for many years and hope to never use them? Personally I get no enjoyment or satisfaction navigating using a paper chart, in the same way I get no pleasure whatsoever using an AA roadmap when driving my car. My boat and my car have satnav - no hassle, dead reliable, accurate and takes away a chore, so I can relax and enjoy driving my boat or my car. BTW there are many ways to engineer a reliable installation, so worrying over equipment failure shouldn't be a necessary.

[NDG]

Originally Posted by asteven221

Personally - electronics any day! Paper charts? Got them but have not used them for many years and hope to never use them? Personally I get no enjoyment or satisfaction navigating using a paper chart, in the same way I get no pleasure whatsoever using an AA roadmap when driving my car. My boat and my car have satnav - no hassle, dead reliable, accurate and takes away a chore, so I can relax and enjoy driving my boat or my car. BTW there are many ways to engineer a reliable installation, so worrying over equipment failure shouldn't be a necessary.

Its interesting how people's preferences differ. I take a completely opposite approach - its just a personal thing - I like maps and charts and enjoy using them, even a roadmap in a car. They always give a good sense of one's position in the world. I do have a GPS on the boat but I use it to plot positions straight onto a paper chart, but that's about it. I can't imagine anything worse than having a satnav in the car. I like using modern technology - I've got the ipods and digital cameras etc - I just find charts interesting. Its always nice to look at my English Channel passage chart and look at all the old plots and courses over the years that have given it a nicely well-used appearance, and remind me of passages we've made in the past. Dont get that with chart plotters!

[Twister_Ken]

A chart is the whole chart, and nothing but the chart.

A plotter* is looking at the chart through a tiny window.

*Honourable exception - Yeoman.

[AntarcticPilot]

Originally Posted by NDG

Its interesting how people's preferences differ. I take a completely opposite approach - its just a personal thing - I like maps and charts and enjoy using them, even a roadmap in a car. They always give a good sense of one's position in the world. I do have a GPS on the boat but I use it to plot positions straight onto a paper chart, but that's about it. I can't imagine anything worse than having a satnav in the car. I like using modern technology - I've got the ipods and digital cameras etc - I just find charts interesting. Its always nice to look at my English Channel passage chart and look at all the old plots and courses over the years that have given it a nicely well-used appearance, and remind me of passages we've made in the past. Dont get that with chart plotters!

I work with maps as my day job, both making them and using them. It is, like most things, horses for courses. The paper map is the ideal product for some applications; the digital map for others. For leisurely planning, the paper map is much easier to use; for instant decision making, the digital product is better. The digital product allows direct integration with other systems - no "plotting positions" at all! But the paper product shows all the topography in its overall context. A digital map zoomed enough to be useful for immediate navigation does not show an overview; and vice-versa. It isn't better or worse; it is different products for different use patterns.

By the way, it is something of a false distinction these days. Pretty much all modern charts are created and maintained in digital form; the paper product is an output from the digital data. For vector digital products, the digital product should have as much or more detail than the printed chart. This may not be true for raster products.

[orbister]

Originally Posted by NDG

Its interesting how people's preferences differ. I take a completely opposite approach - its just a personal thing - I like maps and charts and enjoy using them, even a roadmap in a car.

I'm with you, brother. I don;t have a chart plotter and I have no intention of getting one - for a start, I can't see how even a huge (sic) eight-inch screen can begin to compare with a proper waterproof daylight viewable, take into the cockpit in the rainable paper chart. I'm a purist there too - no Imray, no pretendy "Small Craft" stuff, only proper, decent, god-fearing admiralty charts on board. Hah.

Mind you, it's GPS every time for finding positions.