do I really need a log?

[Refueler]

Apologies if this is reiterating points already made, but haven't read all as laptop batteries low and no means to recharge.

Working log? Yes, ideally, if less so where I am in the Med where currents are generally slight (and hull growth gives logs a hard time). But so many posters make the point that GPS might die (instrument or signal), whilst every one of us knows that GPS is far more dependable than any log.

More absurd: when I last did an RYA course we were urged always to keep dead reckoning positions "in case GPS failed". This may have changed but to the best of my knowledge it's still the case. Luddite nonsense! Why monitor a guess of your position (albeit an informed guess) when you can plot an accurate one as often as takes your fancy. Should GPS fail, then's the time to start a dead reckoning plot, but you'll know for sure where you were when it started.

The only compelling reason (and it's a good one, if not the one generally promoted) to habitually make a dead reckoning plot is to assess your skills: i.e. to compare that plot to the true one garnered from GPS.

Or am I missing something?

I would defy most people to do a DR while using GPS .... they would naturally bend to using info of the GPS to plot .. so losing the DR format ... in fact it would be more a 'corrected EP !!'

 

[boatmike]

I would defy most people to do a DR while using GPS .... they would naturally bend to using info of the GPS to plot .. so losing the DR format ... in fact it would be more a 'corrected EP !!'

Yes and there is no point anyway. The sensible thing is to note the position every hour (preferably mark on chart) so that if GPS goes tits up you can plot DR from there. You do need practice to become proficient at DR in the first place though. It's no good trying to remember how to do it when the lights go out and you don't know where you are in the first place.....

 

[maxi77]

Yes and there is no point anyway. The sensible thing is to note the position every hour (preferably mark on chart) so that if GPS goes tits up you can plot DR from there. You do need practice to become proficient at DR in the first place though. It's no good trying to remember how to do it when the lights go out and you don't know where you are in the first place.....

I disagree, your basic plan is a DR, and I would suggest that if one is say plotting a GPS position hourly it would make sense to plot a 1 hour DR from each fix just as a check, it does make sense to have some idea where you expect to be just in case you end up somehwer else. Even your passage plan on your GPS is in it's own way a DR, though it gets a bit problematic recovering it if the GPS device goes tits up on you.

 

[Pye_End]

your basic plan is a DR

Agreed. Doing a passage plan almost always assumes a certain speed through the water - particularly where you need to work the tides to your advantage. If you deviate from your assumed speed through the water then you may need to do something about it, particularly where tides are of a significant rate or tidal gates are experienced.

Knowing speed through the water is useful, but perhaps may be less critical now with the larger and more reliable diesels. Quicker hull speeds mean that working the tides becomes less important.

 

[boatmike]

I disagree, your basic plan is a DR, and I would suggest that if one is say plotting a GPS position hourly it would make sense to plot a 1 hour DR from each fix just as a check, it does make sense to have some idea where you expect to be just in case you end up somehwer else. Even your passage plan on your GPS is in it's own way a DR, though it gets a bit problematic recovering it if the GPS device goes tits up on you.

I think I have tried to show on this thread how strongly I feel about maintaining traditional methods of navigation. To deny the accuracy of GPS however is plain stupid. No DR will give you positional accuracy to compare with GPS and unless I had other evidence to support it ( from depth contours, bouys, land fix etc) I would accept a GPS position as more accurate than DR anytime. A GPS position is NOT a form of DR and your assumption is incorrect. DR is well defined in text books and has B all to do with GPS, Radar, or any other aid. If you always maintain a paper plot and record your EP every hour the objection to reliance on GPS goes away. If you want to calculate the DR every hour then fine, do so. However it is also "traditional" to accept all other evidence from aids to navigation when adjusting an "ESTIMATED POSITION" derived purely from DR and GPS is only one of these but a very very good one. In fact if GPS said one thing and DR said another I would be more inclined to adjust my EP to the GPS position than vice versa but before doing so I would look at all other information available to me as well.
I repeat. If you record your position each hour and are prepared to continue at any time by DR if the GPS goes down then there is absolutely no reason not to do so and to keep a running DR by first principles is expending "wattless energy".

 

[ninky]

there is a more philosophical / esoteric reason for maybe using traditional over gps and that is gps relies on 4 US govt satellites. they could be switched off (unlikely i know). can they not also tell where you are (should they be interested) in the same way any mobile phone gives aways your exact position?

there's something liberating in the ability (and confidence) to be somewhere unwatched. (have i been reading too many conspiracy theories? - i'm not really that paranoid!). and relying totally on your own capabilities.

 

[Gunfleet]

But I bet if you are out of sight of land you write down your gps derived position every so often. I do.

Before you 'blow me away' - I am a trained Ships Navigator ... Sextant and all the rest of traditional ways as well as later electronic. I can put a dot on the chart mid ocean if need-be. Do I bother with trad methods ? Rarely ... why ? I enjoy my sailing and get on with that ... if a GPS gives me what I need ... then so be it. It allows me to sort something else.

 

[planteater]

there is a more philosophical / esoteric reason for maybe using traditional over gps and that is gps relies on 4 US govt satellites. they could be switched off (unlikely i know). can they not also tell where you are (should they be interested) in the same way any mobile phone gives aways your exact position?

No, they can't determine your position. They simply transmit timing signals that are used by your receiver to calculate position. As long as you don't connect your GPS to a transmitting device your whereabouts remain confidential.

Of course, there are good reasons to transmit your GPS position such as AIS, DSC and EPIRB.

 

[Evadne]

I keep a "DR" while navigating out of sight of land. I use my handheld GPS in the same way as I would a handbearing copmpass, i.e. set a WP and get a bearing and range, then plot that on a paper chart. I would be astounded if anyone capable of skippering a yacht was incapable of such an exercise, and have difficulty in seeing that doing anything less is still responsible navigation. You can plot a handbearing compass fix as well, which I do when I can't be arrsed to switch the GPS on.

Most of my navigation is in the Solent, however, when I don't need a chart or a gps to tell me where I am. That's not boasting, it's just a few years of experience and knowing your own patch. The difference between navigation and pilotage is a subtle one sometimes, especially to the uninitiated.

 

[jonjo]

I cannot think of any situation, in the last 3000 miles of UK coastal and offshore sailing, when my log made an essential contribution to navigation.

 

[TamarMike]

"Material World" on radio 4 yesterday was about the English astronomer who spotted an extraordinary solar eruption in September 1859 that created the most brilliant and extensive auroras ever witnessed on Earth, and which put out of action the newly-built telegraph networks. The impact of such a storm on today's telecommunications infrastructure could be huge. Apparently the electronics in all satellites would be fried (in addition to minor problems such as knocking out all power supply grids around the world for several months). Some scientists believe we are overdue another such phenomenon.......

 

[Refueler]

there is a more philosophical / esoteric reason for maybe using traditional over gps and that is gps relies on 4 US govt satellites. they could be switched off (unlikely i know). can they not also tell where you are (should they be interested) in the same way any mobile phone gives aways your exact position?

there's something liberating in the ability (and confidence) to be somewhere unwatched. (have i been reading too many conspiracy theories? - i'm not really that paranoid!). and relying totally on your own capabilities.

Only 4 ? There are far more than that up there ... but your set may only see or use 4 ... Sirf sets can use much more ... some 12, 16 sats or more if visible.

 

[Refueler]

But I bet if you are out of sight of land you write down your gps derived position every so often. I do.

Funny enough it depends how I feel and where I am ... delivery - I'll keep a rough log and dot on a chart purely as a record of what I did with their boat .... on my own ? rarely.

 

[sailor211]

if I wanted to save money when replacing old instruments do I really need to go to the expense of fitting a new log and head unit? Sure its a nice to have but with the marvels of GPS plotters I can see my SOG and read off my track distance too. Am I missing anything? (unless of course the GPS goes down)

will you promise to go past my mooring at no more than 4kts(water speed) the speed and not 7 kts sog and swamp my dinghy with your wash?? if you so keep your water speed to the limit fine, so many boats use sog becasue they do not look at a log

 

[Seafort]

Erm why?

I keep a "DR" while navigating out of sight of land. I use my handheld GPS in the same way as I would a handbearing copmpass, i.e. set a WP and get a bearing and range, then plot that on a paper chart.

Might just as well plot the GPS position as a fix and label it GPS. Bearing and distance off will be calculated from this so why add an additional "Fudge factor".

Mind you I do know how much of a pain a small chart table can be.

Dave.

 

[jonjo]

But I bet if you are out of sight of land you write down your gps derived position every so often. I do.

Not that often. The Navtex keeps an electronic log and I always check the battery level of the reserve GPS.

Fog or a lurking customs cutter always prompt some pencil & paper activity at the chart table.

 

[Refueler]

Not that often. The Navtex keeps an electronic log and I always check the battery level of the reserve GPS.

Fog or a lurking customs cutter always prompt some pencil & paper activity at the chart table.

Don't tell anyone but I don't know any plotter that doesn't keep a record of track .... which does not erase when power goes off ... only time it erases is in catastrophic failure of the plotter.
As I keep a watchful eye on my plotter while wandering the waters deep - I have a pretty good idea where I am on a chart even without a pencil mark. Unlike some - as soon as I don't need plotter for fine detail work - I zoom out to have a 'realtional position' to nearest land ... even if it means extreme zoom out ...

as here crossing Baltic Gotland - Swedish Archipelago ....

 

[blackdogsailing]

D.R & E.P

Please correct me if I am wrong but I have always been taught that a DR position is solely based on course steered and distance run by log. It takes no account of set and drift. An EP however does. My question is; if you navigate by 'dead reckoning' are we in fact using the expression to include set and drift ?

Chris

 

[Refueler]

I disagree, your basic plan is a DR, and I would suggest that if one is say plotting a GPS position hourly it would make sense to plot a 1 hour DR from each fix just as a check, it does make sense to have some idea where you expect to be just in case you end up somehwer else. Even your passage plan on your GPS is in it's own way a DR, though it gets a bit problematic recovering it if the GPS device goes tits up on you.

Mine isn't !! Mines a passage plan that is a resultant of whatever I expect to encounter. If on passage I am not making what I planned - then I alter my passage actions to make it so.
Mmmmmmm that still doesn't explain it !! What I'm saying is my planned course line and ETA's is a result of my sailing actions. It's not a DR plan, it cannot be. I agree that initially you would think it, but it's not. It's the resultant of you making True course xxx and true speed x - by whatever means necessary.

So on passage you would be correcting course, speed to make the planned course line.

So please explain how a passage plan can be a DR ? Whether that PP be on a plotter or chart or PC plotting.

Second what a waste of effort plotting a DR from a GPS plot ... Now if you said an EP based on positions so far found by GPS / tidal info etc. that makes more sense ... because then it would be closer to reality. DR is a cross on a chart that really is a last ditch effort to say ... Well somewhere around there maybe.

When I have people on my boats and they haven't nav'd before ... I'm more than happy to show my limited knowledge of nav from shipping days ...

Delivery job ....

Shows my rough log, chart in use and gear ...

My personal plotter I carry 'just in case' ...

The useless piece of cack that tried to pass itself of as a plotter / nav centre ..... even when we found the right chart card - it was still a mess !! (FTI - it was checked out before delivery by Raymarine agent ... AOK, checked after delivery ... AOK ... yep a heap of cack !)

 

[Deleted member 36384]

There is one fundamental error in all that ...... most don't venture offshore enough to warrant knowledge of sextant, traditional skills of yesteryear to such extent.
If they can take a few bearings, draw a line on chart ... recognise a buoy against that marked on chart - their OK.

Before you 'blow me away' - I am a trained Ships Navigator ... Sextant and all the rest of traditional ways as well as later electronic. I can put a dot on the chart mid ocean if need-be. Do I bother with trad methods ? Rarely ... why ? I enjoy my sailing and get on with that ... if a GPS gives me what I need ... then so be it. It allows me to sort something else.

Back to log ... one aspect that seems to be missed ... taking my lazy attitude to boating nav ... if I see Log showing x kts and GPS showing some crazy different number ... then I know somethings amiss ... I check it out. If I look around and see buoys, land, marks and GPS plotter appears different ... I check it out.

Blimey - Columbus and Magellan are still alive !!

No they are dead and we are entering a period where political idiots may tell us what we have to do. I go sailing to get away from this. GPS is very reliable but it cant be trusted. My comment was about knowing how to plot position lines when coastal sailing - everyone should at least know 10 uses of a single position line can help determine their position! Astro is another matter which I was not thinking about.

This is my freedom - I do not want irrelevant idiots (politicians) telling me what to do. If a **** wants to buy a vessel and go to sea with no knowledge then I accept the risk of them being in my waters.