Navigation basics

[Bathbuoy]

Can I ask a basic navigation question about using a plotter, in this case the Savvy Navvy app.

Attached is our route from Gosport Marina to Swanwick Marina at high tide 1300 on 16th April. Our draft is 2.5m but even at high tide (4.5m) the route takes us the long way round the deep water channel rather than cutting through North of the bramble bank.

With a 4.5m tide would just staying out of the green drying areas not give us enough water? It seems an excessively long route for us at high tide.

Thanks

 

[Hurricane]

Have a look at the Navionics Web Chart website

Here:-
Navionics ChartViewer
And remember those soundings will be LAT (Lowest Astronomical Tide)

Looks like plenty of water to me.
It has been a long time since I navigated those waters but I seem to remember using the north channel a lot.

 

[MRC]

lots of water in the North channel for you. No need to go all the way around the Bramble bank

 

[Soco2]

You should have between 7-9 meters for the North Channel so yes plenty of water.
maybe it’s just playing safe, however you certainly won’t have any more over Ryde Middle if it takes you near that.

 

[superheat6k]

Can I ask a basic navigation question about using a plotter, in this case the Savvy Navvy app.

Attached is our route from Gosport Marina to Swanwick Marina at high tide 1300 on 16th April. Our draft is 2.5m but even at high tide (4.5m) the route takes us the long way round the deep water channel rather than cutting through North of the bramble bank.

With a 4.5m tide would just staying out of the green drying areas not give us enough water? It seems an excessively long route for us at high tide.

Thanks

Interesting to see such a widely pushed APP being shown to be completely useless.

Unless you draw > 3m, and possibly a good deal more than that, you could sail the north channel on a low water Spring without a fuss. However, relying upon any form of wifi / 3G / 4G driven app for passage planning and navigation is not so wise (IMHO). Better to work upon a principle that land bound modes of modern communication do not always work at sea, indeed even GPS is overly relied upon, as we might soon discover if the Americans decide to take on the Russians over Ukraine.

It is in my view important to learn the basics of coastal navigation using only at most onboard nav equipment of a chart, log, compass and almanac. Then apply Dead reckoning and Estimated position techniques. These are not difficult concepts - remember doing Vectors at school, but will likely need at least some tuition.

 

[jrudge]

I happened to to the north route yesterday around high water. There was 9m for most of it as I recall.

 

[Portland Billy]

You cannot beat an up to date paper chart !

 

[Bristolfashion]

I think that these "auto routes" are great for a "quick & dirty" - how far is it to X etc, but otherwise have to be treated with caution. Having said that, most of the time they are pretty similar to an "old school" route where tide / wind not a significant influence on heading.

 

[Robin]

When we lived aboard on the ICW in USA autoroute on Garmin said various trips could not be done with our mast height but neglected the fact that the bridges that would not allow that route were all lifting ones.

 

[Hurricane]

You cannot beat an up to date paper chart !

Although I agree that the app in the OP is very poor, I can't agree with your statement.
All plotters will provide an accurate position all the time, presented on a moving map display.
So, IMO, as long as the kit works and the electronic chart is up to date, yo CAN beat an up to date paper chart.

 

[Bathbuoy]

Thanks for the replies. It does seem that at that time the minimum depth from East Bramble to Calshot cardinals would have been 8.2m, and we needed 2.5m. But the app routed us out around around West Bramble meaning just this bit was 5.4nm instead of 3nm.

 

[DougOut]

Might be a silly question but doesn't savvy navvy allow you to enter your draft? Perhaps you've got it set wrongly.

 

[Bathbuoy]

In conversations with Savvy Navvy I have been told that their software is at times over cautious at the moment. They are apparently working on making routeings more effective but for the moment prefer to err on the side of caution. I probably would have preferred to have known this before I bought the software as I already have Navionics.

 

[hinch]

did you remember to reconfigure the app for your real draft as the default i think is something silly like 2.5m draft.

 

[Plum]

Can I ask a basic navigation question about using a plotter, in this case the Savvy Navvy app.

Attached is our route from Gosport Marina to Swanwick Marina at high tide 1300 on 16th April. Our draft is 2.5m but even at high tide (4.5m) the route takes us the long way round the deep water channel rather than cutting through North of the bramble bank.

With a 4.5m tide would just staying out of the green drying areas not give us enough water? It seems an excessively long route for us at high tide.

Thanks

I stopped using the Savvy Navvy app a year ago. It does take in to account tidal streams but did not take into account height of tide, just the depth at chart datum. From your experience it sounds like this is still the case but once they fix this flaw I will give it a a try again as in all other respects it works well.

Www.solocoastalsailing.co.uk

 

[Fishtigua]

As Billy said, I still use paper charts, I grew up with them before the days of Apps.

 

[john_morris_uk]

Coming out of Portsmouth at HW I’d be using the inner Swashway up to Gilkicker point. Plenty of water even with 2.5 metres draft. Then follow the coast and use the N Channel as others have said.
Furthermore, as you gain experience, the green bits of the chart are not out of bounds! Just make sure you’ve got enough rise of tide and don’t cut it too fine if the tide is falling.

Edit: It should go without saying that on a motor boat you don’t want your props and rudder touching the bottom. Sailing yachts with those white flappy things can touch soft mud bottoms on a rising tide with impunity...

 

[ShaneAtSea]

did you remember to reconfigure the app for your real draft as the default i think is something silly like 2.5m draft.

Do you put your exact draft into navigation software or do you add a little extra or round it off just to be safe?

 

[Adios]

Its an frightening idea that the skipper of a motorboat with 2.5m draft (how big are we talking?) would rely on an app to passage plan and perhaps consequently is unsure of navigation basics. Come on people how lazy and uninterested in doing things ourselves can we get

 

[Black Sheep]

Its an frightening idea that the skipper of a motorboat with 2.5m draft (how big are we talking?) would rely on an app to passage plan and perhaps consequently is unsure of navigation basics. Come on people how lazy and uninterested in doing things ourselves can we get

I think it's unfair of you to characterise the OP as "lazy and uninterested". On the contrary, we have someone who has joined a boating forum, presumably at least partly to increase their understanding of boating. And someone who has obviously critically evaluated the performance of the software and found it wanting, and come on here to check their understanding. I think that is exactly the opposite of "lazy and uninterested" - it's someone with a genuine interest, who is keen to understand and to learn.