Navionics AIS

[Yealm]

Would you speak ‘2 nautical miles and 3 cables’ for 2.3 nm?

But love the history and romance of bygone language, and the fact that sailors seem to have been the first Brits to use a decimal system...

PS watching a trashy but totally addictive reality show on Netflix - Below Deck - they refer to anchor chain length in 'shackles' - does anyone else use this ?

 

[CM74]

Would you speak ‘2 nautical miles and 3 cables’ for 2.3 nm?

But love the history and romance of bygone language, and the fact that sailors seem to have been the first Brits to use a decimal system...

PS watching a trashy but totally addictive reality show on Netflix - Below Deck - they refer to anchor chain length in 'shackles' - does anyone else use this ?

Yep shackles are standard on big ships, 27.5m - there's a good practical reason as that's the length the chain comes in, so you literally count the joining shackles (ideally leaving one on deck in case you need to split the cable)

I remember frying my brain as a cadet trying to do swinging circles - so many shackles of chain, freeboard and tide in metres, chart depth in fathoms and convert to cables to plot on the chart

 

[laika]

To say “a tenth of a mile” is potentially confusing because the recipient might be unsure whether the mile unit being used is Statute mile or Nautical mile.

If there’s no confusion about “mile” why should there be about fractions thereof?

I do agree with the concept that the best terminology is that which best conveys the meaning. Most people I sail with would have no clue what a cable was and those that did would, like me, convert it to metres in their head to visualise it. Doubtless this might be different if I was sailing with older professional mariners.

If I personally use the the term (as I have occasionally be known to do) the meaning I’m trying to convey is “about 200m and by the way I’m a salty old sea dog”

 

[colhel]

I'm not trying to be silly, but using "cables" isn't relevant to any 'real World' chart is it, or am I missing something?
Alexincornwall, please don't take this in any way as a criticism towards yourself, but in 48 years offshore, and all of my life as a sailor, I've never found anything sensible in it, or having it referred to ever, above metric; it's a one dimensional measurement.
Navionics don't include it as part of my settings, and I wouldn't be as comfortable using it in place of metric.

Thanks for being brave enough to post this, as thanks to this, I've learnt something!

 

[oilybilge]

Cables aside....

My iPad has Navionics with AIS (from VHF via a Yakker) and it works very well. Haven't noticed any of the issues that Alex mentioned.

My only real gripe .... I wish there was visual differentiation between Class A and Class B vessels. When you get a cluster of blobs on the screen -- sailing into Harwich on a Saturday afternoon, say -- it'd be really useful to know which are the ships and which the yachts. How hard would it be to use different colours? I think other AIS displays do this.

 

[Yealm]

Cables aside....

My iPad has Navionics with AIS (from VHF via a Yakker) and it works very well. Haven't noticed any of the issues that Alex mentioned.

My only real gripe .... I wish there was visual differentiation between Class A and Class B vessels. When you get a cluster of blobs on the screen -- sailing into Harwich on a Saturday afternoon, say -- it'd be really useful to know which are the ships and which the yachts. How hard would it be to use different colours? I think other AIS displays do this.

That would be damn useful !
Or be able to specify a colour to represent a user-defined parameter (eg boats over 50m etc etc)

 

[Yealm]

Cables aside....

My iPad has Navionics with AIS (from VHF via a Yakker) and it works very well. Haven't noticed any of the issues that Alex mentioned.

My only real gripe .... I wish there was visual differentiation between Class A and Class B vessels. When you get a cluster of blobs on the screen -- sailing into Harwich on a Saturday afternoon, say -- it'd be really useful to know which are the ships and which the yachts. How hard would it be to use different colours? I think other AIS displays do this.

An important feature I want from AIS is to know respective boat positions at CPA - eg so if in Channel crossing situation you know whether to speed up and sneak across ahead, or slow down and pass behind.
I think OpenCPN has this.

Does Navionics (on iPad) ?

 

[Yealm]

Yep shackles are standard on big ships, 27.5m - there's a good practical reason as that's the length the chain comes in, so you literally count the joining shackles (ideally leaving one on deck in case you need to split the cable)

I remember frying my brain as a cadet trying to do swinging circles - so many shackles of chain, freeboard and tide in metres, chart depth in fathoms and convert to cables to plot on the chart

In one episode, the boat (60m) spun around a lot at night (I think rookie deckhand on watch) and the next morning the two anchor chains were horrendously tangled !

 

[davidaprice]

An important feature I want from AIS is to know respective boat positions at CPA - eg so if in Channel crossing situation you know whether to speed up and sneak across ahead, or slow down and pass behind.
I think OpenCPN has this.

Does Navionics (on iPad) ?

BCPA (Bearing of Closest Point of Approach) would tell you this, but from memory that's missing from the Navionics app. I remember thinking exactly this, that knowing that closest point of approach will be 300m in 6 minutes is not as useful if you don't know if you'll be passing in front or behind. (And does CPA take into account the length of the ship?)

 

[oilybilge]

Wait, it seems I was wrong about the Class A/Class B thing. They both show as green, but they're different shapes. I'd never noticed!

There's no CPA function like you describe, but you can get it to draw a line from the bow of every vessel (including yours) that shows where it will be in x minutes. That's pretty useful. And any vessel on a collision course with you turns red. Also useful.

 

[davidaprice]

There's no CPA function like you describe, but you can get it to draw a line from the bow of every vessel (including yours) that shows where it will be in x minutes. That's pretty useful. And any vessel on a collision course with you turns red. Also useful.

If you've got the Navionics app open now and AIS active, click on any AIS boat and I think you'll get a pop-up of its details including CPA and TCPA, but not BCPA.

 

[Yealm]

BCPA (Bearing of Closest Point of Approach) would tell you this, but from memory that's missing from the Navionics app. I remember thinking exactly this, that knowing that closest point of approach will be 300m in 6 minutes is not as useful if you don't know if you'll be passing in front or behind. (And does CPA take into account the length of the ship?)

Thanks that's really helpful.

 

[Yealm]

If you've got the Navionics app open now and AIS active, click on any AIS boat and I think you'll get a pop-up of its details including CPA and TCPA, but not BCPA.

Just a quick question - am i right to assume the Navionics iPad works by getting AIS data from an onboard AIS receiver/wifi transmitter unit ? (as opposed to from internet based AIS apps ?)

 

[davidaprice]

Just a quick question - am i right to assume the Navionics iPad works by getting AIS data from an onboard AIS receiver/wifi transmitter unit ? (as opposed to from internet based AIS apps ?)

Yes, see here: AIS in the Boating app

 

[TSB240]

An important feature I want from AIS is to know respective boat positions at CPA - eg so if in Channel crossing situation you know whether to speed up and sneak across ahead, or slow down and pass behind.
I think OpenCPN has this.

Does Navionics (on iPad) ?

No
I find the navionics ais display very poor for anti collision use. The open CPN display is far more use in showing relative position especially in relation to close contacts. It will clearly show and update your CPA and if you are going in front or behind your close contact.
This is far more value and very reassuring in poor visibility.
I do get worried by the number of people that seem to be looking at their chart plotters and AIS reports In good conditions when eyeball or binoculars and the human brain should be guiding their navigation and not electronic dependent.
Navigation is not about where you currently are it is about where you are going to be in the next few moments. A moment may be seconds, minutes, hours or days!

 

[DipperToo]

No
I find the navionics ais display very poor for anti collision use. The open CPN display is far more use in showing relative position especially in relation to close contacts. It will clearly show and update your CPA and if you are going in front or behind your close contact.
This is far more value and very reassuring in poor visibility.
I do get worried by the number of people that seem to be looking at their chart plotters and AIS reports In good conditions when eyeball or binoculars and the human brain should be guiding their navigation and not electronic dependent.
Navigation is not about where you currently are it is about where you are going to be in the next few moments. A moment may be seconds, minutes, hours or days!

+1 for OpenCPN. It would be really nice if someone developed a small standalone App for a phone using the OPenCPN AIS plugin so rather than looking at a small phone screen cluttered with chart data, you could see a very meaningful AIS display with all the CPAs etc cleanly displayed.
From the several packages I have seen, OpenCPN must rate as one of the best for CPA management and clear display without having to look at specific targets and pull up their data like many other approaches.

 

[laika]

I do get worried by the number of people that seem to be looking at their chart plotters and AIS reports In good conditions when eyeball or binoculars and the human brain should be guiding their navigation and not electronic dependent.

out of interest, how do you know how many people are doing that?

regardless, although my AIS tends to be off for most inshore sailing, I will have it on and check what it's telling me when crossing traffic in good conditions. AIS will tell me CPA of a vessel long before I've got useful info out of a hand bearing compass. And I'll argue that in such a situation, if fitted, AIS info falls under rule 5's "all available means appropriate in the prevailing circumstances and conditions".

Like the navionics app I find it a bit disappointing that there's no BCPA on my old ramarine chartplotter meaning my "ahead or astern?" question needs to be addressed by letting out the sails and seeing whether CPA goes up or down.

 

[alexincornwall]

An important feature I want from AIS is to know respective boat positions at CPA - eg so if in Channel crossing situation you know whether to speed up and sneak across ahead, or slow down and pass behind.
I think OpenCPN has this.

Does Navionics (on iPad) ?

Navionics won't do that but if you happen to be using Vesper transponder, their own WatchMate app will do this. It's a very useful feature.

 

[Yealm]

Gosh, so Navionics AIS not really that useful !

On the other hand, the Open CPN website is pretty clunky.
Got a simple question - if I put Open CPN on a Mac laptop, can I input all the data (GPS, AIS etc) to it via wifi (presumably as some kind of NMEA format) ? Or does it need some cables?

 

[MoodySabre]

Of course Navionics can do that. That's the whole point of AIS. Of course it needs data from a wifi source.