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Using MARPA instead of AIS…

Returning to Brighton from Dieppe recently I realised that the AIS was not working, but had not time to fault trace or fix it so I thought I would revisit using the radar in earnest.

This is crucial given that the Traffic Separation Scheme that separates the Channel into two one way traffic streams for large vessels adds to the excitement for a yacht – as they say a “tortoise crossing the motorway” – gives you some idea of the experience.

DSC01864The rather shaky photo here – sorry but we were bouncing up and down a bit! – and I didn’t want to leave the helm too long just to take a photo! – shows the MARPA targets acquired on the Raymarine (C120 + Raymarine Radome 2kw) – click on the image for a larger view.


Just like the AIS you must take the heading, speed, and collision DSC01865avoidance data with a pinch of salt. I have seen a moored cross channel ferry registering 17kts on the AIS – and so it is here – this screen shot shows variable quality of data eg. was the second vessel in this MARPA list really doing 33kts ! – also the vessels were all clearly on a heading of about 250 degrees magnetic, but the heading data on the display shows the vessels going in all sorts of directions…

The bottom line is that standing in the cockpit with a pair of binoculars and taking bearings was my chosen primary source of data…and although we had bowled long from Dieppe for some 8 hours on a close reach doing 6.5 to 9kts with only the occasional sail trim adjustments… I was forced to reel in the genoa and come to a standstill to let an imposing cargo vessel from Iran thunder past.

Good decision as it turned out since it took a good 10 minutes to cross the wake after it had passed by!.

Track MARPAThis screen shot shows our track as we took avoiding action and then tried to get underway again before the next charging container vessel came barreling down the track.






“No Ais” – on Raymarine C and E Series

DSC01879It is annoying that the Raymarine C and E series which have an AIS interface have no displays to show whether AIS is actually working but has no data to display.

Both these displays simply say “No AIS” in the top right hand status corners of the screen. From the software developers point of view they probably would say indignantly that this language is consistent with the message displayed before the GPS Fix is obtained – in other words “No Fix”.

But the difference is this:

1. “No Fix” means the GPS is still obtaining satellite and the chartplotter is calculating the position of the boat. After few minutes if no fix is still displayed you know the GPS is not working and you need to fault trace. So the passage of time adds another piece of vital data that helps you decide that something is wrong (assuming the USA has not declared war and switched off the whole GPS system!)…whereas…

2. “No AIS” means two different things –
a. the AIS is fully functional, is receiving transmissions, but there are none to display, or
b. the AIS is NOT fully functional, is NOT receiving transmissions, and you need to due some fault tracing…straight away

This means you can set sail unaware that the AIS is faulty – but you would be totally aware if the GPS was faulty.

Please Raymarine, do something about AIS error detection – a suitable button could live nicely on the MARPA/AIS settings toolbar.


GPS Terminology – nanu nanu :-)

After the last post I had a few emails asking me what PRN 32 means so I thought I would list a few terms that you may come across if you start looking into the GPS system..

SV – Space Vehicle
PRN – Pseudo Random Noise
NANU – Notice Advisory to Navstar Users – there is a free mail list service run by the US Coast Guard to send GPS watchers an automatic status report.

For the latest nanus see the US Coast guard site here.

BTW its called Navstar because that is the correct title of the US military GPS system


Raymarine share price rockets…

Raymarine - ProductsGarmin is the mystery bidder behind a takeover approach for Britain’s Raymarine Plc. Garmin’s approach could be worth as much as 200 million pounds ($389 million)

Raymarine Plc has two sites in Portsmouth, Hampshire. Corporate headquarters are based in Anchorage Park, and house the Factory service and Repair facility. Quay Point is the engineering and design headquarters. Raymarine floated on the London Stock Exchange on 6 December 2004, and was a landmark event in the long and successful history of Raymarine.

A number of private equity companies are also thought to be eyeing Raymarine, officials at Raymarine were not immediately available to comment.


Updating the C Series firmware v4.25

I have just got round to updating my C120 (all comments here relate to all C-series plotters) and thought I would put in one place all the relevant FAQ’s on the Raymarine site. You will have to have a Raymarine account to see these FAQ’s so register its well worth it.

First download the v4.25 software – product registration is required.

The main instructions for the upgrade process are FAQ 1219 these are comprehensive and accurate and list a variety of other FAQ’s to read on a variety of subjects like which CF card to use and so on..I am not repeating all that here. Instead I am listing some FAQ’s that I think will help you overcome errors that you may encounter – mostly by not following the instructions !

Being in IT I believe I have a healthy scepticism when it comes to “following the instructions”… in other words, I always follow the instructions totally literally… and then when it goes wrong, knowledge, experience and gut instinct kick in and then the real work begins;-)

But I can recommend that you follow the instructions here – totally literally – they work faultlessly… up until almost the last step… step 9.

Here is my advice…..

Step 9. In step 9 you are advised to remove the upgrade CF card – you must remove it.
Step 10. In step 10 you press reboot – DO NOT put your Navionics card back in (as I did – this is how I know!)
Step 10.1 Let the C-Series boot

C120 UpgradeStep 11 Press OK to verify that the software version shown is v4.25. If this does not happen you need
FAQ 1138

Step 12 Wait for the default map to load – in my case a map of the UK
Step 12.1 Now insert the CF card containing the Navionics chart software
Step 12.2 The software is automatically loaded and the boat appears on the chart in the correct location.

Not a major problem – but care needed just at these last few steps.

So well done to the software team at Raymarine – Its wonderful to see how a totally embedded and controlled operating system and proprietary software works so flawlessly….oh well, back to Windows Vista on my laptop now….:-)