AIS Junkie ....

[ParaHandy]

Overheard this conversation .. “got QM2 MMSI at Nab Tower on ‘er way to New York and guess what? Her call sign is GBQM ….. wow … wot about that, then?”

Erm … this is marine equivalent to trainspotting with spotty youths clutching their radios in anoraks?! No drugs, mind, altho’ do get chance to follow the Donald Redford for high prozac tension (will she, won’t she?) excitement ….

Righto … trundled out into eastern solent with NASA AIS engine for final pre-screw-it-in trial, SeaClear + Glomex whip aerial gaffer taped to pushpit and picked up everything expected to a limit of 8-10m radius except Wightlink ferries which don’t have AIS even though they are passenger vessels and weigh a good deal over 300 tonnes. Red Funnel ferries do have AIS …. Get a grip Wightlink ….

But …

The SeaClear package (which is free) drops an AIS target after 4 minutes and given that the NASA AIS can only receive on one of the two transmission frequencies (ships alternate their AIS transmissions on 2 frequencies and there is normally plenty of opportunity to receive data) there is a good chance that you’ll miss ships at anchor and the static details such as the vessel’s name can also be missed as these are transmitted at 3 and 6 minute intervals respectively. Also, the NASA AIS engine when used to pass-through GPS data frequently fails to pass the GPS data for periods up to 14 seconds. NASA deny their engine gets overloaded but can not see any other reason for this as disconnect the VHF aerial and GPS data flows through uninterrupted. (thanks to All-gadgets for trying to sort this and for supplying the kit) And, I fitted a mast-head steel whip antennae to the pushpit which works better than some …

However …

The SeaClear CPA & TCPA is bluidy good. The NASA AIS engine picks up transmissions eg vessel 23+kn is received nearly every 4 secs (allowing for 50% transmission loss on the other frequency). There is another package from ShipPlotter (25 euros) which keeps a ship database indexed by MMSI numbers and shows vessel name to be displayed as soon as dynamic data is received but this package has no CPA and is more use for shore-based anoraks …

Cost …

Unusually, for something as potentially useful as this, total cost minimal at £150 all including aerial. Charts good enough for use with SeaClear from here and anyone having problems can PM me and I’ll email calibrated south coast charts …

This AIS does seem to give you a level playing field in the wild-west out thar' when avoiding the bastids in fog … it complements radar but will never replace it etc etc + more guff to satisfy luddites out there !!

The chances of the full AIS (transmission & reception) becoming mandatory for vessels under 20mtrs is, I would have thought, nil. The two areas in the world concerned about bandwidth overload are the Malaka Straits and North East/South UK and plans to commercialise the system with email, weather and VTS interrogating ships would scupper any spare bandwidth anyway. All imho.

And thanks to …

Jock McHacker, Scottish/Swedish pioneer of Self Organizing Time Division Multiple Access (SOTDMA) data communication technology for inventing the thing …

 

[claymore]

You do need to get out more.
The celebrated Claymore laptop and package can have AIS integrated onto it but the number of ships out there in the sacred waters of the west coast are few let alone ones who will have DSC and or AIS so I think it would be a waste of money and I'm so happy with my underbunk anti condensation stuff that I feel entirely capable of living an AIS free life
Thank you

 

[ParaHandy]

ah ken yer wallet nivver gets a run oot these days efter yon ebespasher debacle but wud it nae been cheaper wi' yin orra yon air-freshener things tae keep oor swetty airses' aereated?

 

[claymore]

Dear Heart has taken up ra crocheting an is developing a line o' grundies fer ra likes o youse - wiz it Ron Hill who first ran in a string vest - weel she came up wi a pair an ah said they'd be fine fer ma guid sel, but no' fer Para as the holes wiz ower big an ye'd hae a job keepin yer wullie tucked in - despite whit Isla says

 

[ParaHandy]

Oban branch M&S ...

youse miserable auld goat, gettin' ra dear heart tae knit yer grundies. hae youse nae shame? ah've posted this erudite and thocht-foo piece orra reasearch in ra wrang place ....

 

[jonjo]

[ QUOTE ]
SeaClear + Glomex whip aerial gaffer taped to pushpit and picked up everything expected to a limit of 8-10m radius

[/ QUOTE ]
Is this a standard VHF aerial? If so the AIS setup provides an emergency aerial as part of the bargain.

[ QUOTE ]
Also, the NASA AIS engine when used to pass-through GPS data frequently fails to pass the GPS data for periods up to 14 seconds.

[/ QUOTE ]
Do you have an alternative configuration that fees GPS data into the Seaclear software? If not the CPAs might become unreliable.

 

[Amphitrite]

An alternative would be to feed GPS-data by way of a USB-Serial convertor.
BTW, transmission of weather info is already defined by IMO and used in Malakka Street and Great Lakes. I also heard about trials from Nab Tower.

 

[ParaHandy]

yes, the CPA is continuously re-calculated in SeaClear and theoretically there could be an error if GPS data fails. In practice, however, the most frequent data loss is 6-8 seconds which would not be an issue. SeaClear maintains the last GPS data until refreshed otherwise there could be a problem. I deliberately chose this method of feeding the GPS data through the AIS for other, important, reasons and was somewhat miffed to see it dropping data (the data is fed thro' USB serial converter).

not sure what you mean by "includes an emergency aerial". Is this a packagage on offer elsewhere? The one serious issue is range. With my aerial position, you begin to lose AIS data at a range of 8-10 miles but I should have qualified this by mentioning that was for a X channel ferry whose superstructure is tall whereas a fully laden tanker may well be much lower in the water. At that distance, the ferry's bridge is just visible. So, an emergency aerial would have a very limited range?

 

[jonjo]

[ QUOTE ]
not sure what you mean by "includes an emergency aerial".

[/ QUOTE ]
I was not clear whether the aerial was specifically tuned to the AIS frequencies? If not then you have something left on which to transmit if the mast goes overboard, but I take your point about limited range.

Re. the 4 minute disappearing target issue... reading through the SeaClear manual this evening I noticed this setting is defined in an .ini file and presumably can changed. Seaclear also maintains a 60 minute target DB so I assume that once a ship's extended details are in the DB a reacquisition from a short AIS position squawk, within the 60 minutes, will light up the target with full details.