Paper Charts?

[Beelzebub]

I always use electronic navigation aids as just that:- aids to traditional nav. When a GPS system gives me a position that agrees with my own DR, I am happy that someone else agrees with me.

However, I will never stop plotting tidal calcs, handheld compass bearings etc on the paper chart.

And it goes without saying that offshore the sextant gets a good airing

 

[[194224]]

I always use electronic navigation aids as just that:- aids to traditional nav. When a GPS system gives me a position that agrees with my own DR, I am happy that someone else agrees with me.

However, I will never stop plotting tidal calcs, handheld compass bearings etc on the paper chart.

And it goes without saying that offshore the sextant gets a good airing

I operate much in accord with your philosophy. The point that comes to mind though is how likely is a DR going to be close to a GPS derived position if you are sailing in tidal waters and have travelled some distance from your last DR or fix? EP yes, that should stand a better chance. The additional question a navigator has to ask AND answer is what would I do if/when my EP/DR and GPS position do not agree. I suspect you probably have the skill and experience to answer that so please don't think I am knocking you in any way; I am not. Personally I just think the DR position is likely to be of little value as its divergence from reality can be significant in tidal areas, particularly under sail where leeway may need to be considered too.

If pressed, I would guess that if such a discrepancy were to be noted by the navigator the vast majority of them would back the GPS position and proceed from there but seek further confirmation if possible.

 

[RunAgroundHard]

... how likely is a DR going to be close to a GPS derived position if you are sailing in tidal waters and have travelled some distance from your last DR or fix? EP yes, that should stand a better chance. ...

Here are a load of old forumites discussing this. Question for expert navigators

 

[[194224]]

Here are a load of old forumites discussing this. Question for expert navigators

Ah, I'm already wishing I'd said nothing

 

[Daydream believer]

Ah, I'm already wishing I'd said nothing

So do we

 

[requiem]

Ah, I'm already wishing I'd said nothing

Oh no, this is fun!

GPS is merely one method of getting a fix. Radar, visual, and celestial are also options (and the depth sounder may also be of use. If close to shore. As a general principle one should never be reliant on only a single source (which is why I get snobby about popular nav apps that make it hard to plot other types of fixes).

But, a DR or EP is ultimately an estimate rather than a fix, which puts it much lower on the confidence hierarchy. If the two agree, or are realistically reconcilable, that is fine. If you look at the GPS status and see the HDOP is reading something like "16482" rather than say, "3", that would be a sign that you might not want to ignore the DR.