How are you using AIS?

Anyone have or using formal or informal guidelines / procedures for using AIS displays? What target information is displayed on ECDIS? Is it every mate for himself or is there a policy?

I’ve been shutting off the AIS display on one radar and using APRA only on one display, AIS on the other radar. One of the mates told me that his last ship they were required to use APRA inside a certain range.

Most boats I’ve been on it’s a free for all. It bugs me that it can be nearly impossible to select a radar target when it has an AIS symbol on the radar but I’ve figured out ways to do it. I’m constantly trying to educate mates about AIS vs ARPA and how AIS isn’t supposed to be used for collision avoidance. Many people prefer it because it seems so much more precise, since it’s GPS based, but don’t realize that they’re trusting the other ship’s GPS.

My routine:
One RADAR for navigation: AIS targets displayed, True vectors. True Trails ON.
One RADAR for collision avoidance: NO AIS targets displayed. Relative vectors, True Trails ON.

Furuno RADARs have a stupid “Fusion” mode that DOES NOT allow for true ARPA plotting if AIS is displayed on your collision avoidance RADAR.

ECS/ECDIS: AIS targets displayed. Most ECS/ECDIS will (in my experience, I’m probably wrong) only display True vectors of AIS targets.

If you don’t have ARPA then learn how to use your EBLs to quickly determine risk of collision.

NEVER use AIS for collision avoidance.

NEVER use AIS for collision avoidance.

NEVER use AIS for collision avoidance.

NEVER use AIS for text messaging.
ALWAYS use AIS for target information OTHER THAN CPA/TCPA.

NEVER trust that AIS information coming from a vessel other than your own is reliable. It’s often bullshit.
ALWAYS check your own AIS dynamic information.

Love and kisses,


In what way does it not allow ARPA acquisition?

As I understand it, and in actual use, it combines the ARPA and AIS information into what, in my opinion, is not a reliable plot. I’ve been know to be wrong, of course, but no one has ever been able to explain to me:

  1. The point of this “Fusion Mode”
  2. How to deactivate it while also displaying AIS targets, which should not be displayed on a collision avoidance RADAR anyway.
  3. How it isn’t just some stupid marketing gimmick, as it’s not an IMO requirement for ARPA RADARs.

Have you read the manual? This is from the manual for the FAR-2107/FAR-2807:


I work temp jobs all over and go from ship to ship so the first thing I do is always figure out if there are any ship specific or Captain specific requirements. Usually there are not. While each Captain will be different, just going by the Masters Standing Orders shows me that most of those differences in my line of work are quite small and they all read in a similar manner regardless of the ship I’m on. So the differences to me are pretty minor.

All of the vessels I’ve been to recently give me plenty of screen real estate so to speak (three radar monitors and two ECDIS units).

The prime radar for collision avoidance will not have AIS overlay on unless it’s easy for me to acquire the radar return as opposed to the AIS icon. The second radar will have AIS on and mainly be used on varying ranges up and down while leaving the collision avoidance radar set as it is.

At least one of the ECDIS units will have the radar overlay on. It will also have the AIS feed on and of course show true motion.

I use AIS for the names of the ships around me in case I need to contact them.


Most of the vessels I work on do not have either a gyro, ARPA or ECDIS.

Most tugs that I go aboard have two unstabized (no gyro input) heading up small Furuno radars and an ECS, such as Nobeltec or Rosepoint. There normally isn’t any radar overlay on the ECS. The AIS is normally not displayed on the radar. Under these circumstances, the AIS displayed on the ECS becomes the initial collision avoidance tool. AIS targets, or their predictor lines, usually show up on the ECS before the targets are acquired on radar.

Normally, one radar is on 3 mile range and the other will be 12 most of the time. I use the radar EBLs and a practiced eyeball on any target that looks like it might be an issue. I tell the mates to do the same thing.

I still see a fair number of older tugs that do not have an ECS, or have an ECS, but do not have the AIS linked to the ECS. I carry a laptop with both Nobeltec and Rosepoint and have a wifi adapter that will attach to about two-thirds of the onboard AIS units that I encounter.

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As previously stated, never use AIS for collision avoidance.
I had an AIS target displayed today that showed a local ferry doing 23 knots backwards; the AIS symbol then jumped about 4 cables ahead of the radar target which would have been interesting if it had been foggy.
i mostly use it for target identification in VTS areas until it gets too busy and starts to clutter up the screen.

Eastbound in Malacca Straits one time, coming up on One Fathom Bank, that’s where the TSS begins. Ships westbound are fanning out and eastbound ships are funneling into the eastbound TSS lane. Chief mate on watch, calls me, says he needs assistance. CM had been saililng master longer then me so I knew it was going to be bad.

Dark, torrential rain, nothing ahead could be seen. The rain was so heavy all the APRA target vectors had washed off on both the 3 and 10 cm. Lots of traffic, all we could see was the AIS display. Those monster container ships at 24 kts about.

We used AIS for collison avoidance till I managed to tune the 10 cm up better and got so we could match up AIS with a radar return, then when the rain let up a bit to get the ARRA vectors going again.

Might be wise in some cases to keep an eye on the AIS info to see if it matches up with APRA.


Yes, I like to compare the two and frequently have vectors from both on the radar. It’s just frustrating how difficult it can be to acquire an ARPA target instead of AIS.


I do the same and have edited my standing orders within the last year to specify that only ARPA targets will be acceptable for collision avoidance. It is shocking how few of the mates know they are not tracking an ARPA target when the AIS target has been designated.

I am also finding a total lack of skill in tuning the radar. I regularly come up for coffee in the morning and find the sea state and rain clutter knobs turned way up with the gain pegged out and clear skies and smooth seas. Trying to explain to some mates that they are going to prematurely wear out the magnetron draws blank stares. I try my best to have my officers leave my ship with a better understanding of how radars work, but who knows if they even give a shit.

As for ARPA the within a certain range thing. I love true trails and want to see ARPA plots on anything forward of the beam that is moving and some things abaft the beam that are moving fast (per the trails).

These are all great electronic aids, but some serious training and ground rules must be present to approximate safe navigation.

Good topic by the way…

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I have had Captain’s in the past who thought a properly tuned radar was one where the sea and rain were all the way down and they got rid of the clutter by turning the gain down to 15%. Gain sould normally be run at ~80% unless it’s really shit weather and you can’t declutter the scope. (In really good weather at that gain you don’t need any STC or FTC.)

Fuck the magnetron, I’d rather not hit a wooden fishing boat.


My three year old JRC’s aren’t the best equipment, but they can see a gnat fart with minimal power on the gain and the tuning done properly. I’ve worked with other radars that had their own idiosyncrasies but most have a sweet spot that does not require 80% power at all times. Mind you, this is in clear and calm conditions. Once it starts kicking up, I do not care if you start adding power to see smaller softer targets.

The problems I see the most are that the mates try to tune out ALL of the feedback, including the back scatter from seas within a mile of the ship once the weather starts building. How are we going to see a wooden boat at 6 miles if there is no return on the scope?

You will have to pardon me for trying to run my ship effectively and economically I suppose.

Yes. With STC and FTC all the way down in calm seas turn the gain up until you see background speckling on the whole screen (ie. not sea return), then turn it down just until that goes away. I’ve worked on some radars where that was closer to 65 or 70%. I would highly doubt your radar is much below 60% ideal gain.

Oh yeah, that bugs the hell out of me too.

I just went through the JRC 9100-series manual to be certain – The gain control changes receiver gain; it does not affect the transmitter. Transmitter power is fixed, but at a given range setting there will be a selection of pulse widths available. Transmitter power and actual pulse widths available are controlled by the scanner or t/r unit in use.

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My standing orders require the mates to do a complete tuning each time they come on watch. None of the mates I’ve had in the last 10 years could do it properly. Most of them figured that “auto tune” would do it for them. Auto tune fine tunes a RADAR that has been properly manually tuned. They love to set up a “too good to be true” display so that the picture is nice and clean and dangerous.

I require mates to use relative vectors and true trails on the collision avoidance RADAR. There is a mantra in my wheelhouse for collision avoidance RADAR use: HUNT FOR TRAILS. Anything leaving a trail is moving. Duh. Slapping an EBL on a moving target lets you quickly decide if it should be ARPA tagged. A quick offset EBL swung on their relative motion line in conjunction with at minimum CPA VRM gives you an idea of possible unacceptable CPA. They’d rather be lazy and look at the AIS for CPA/TCPA. Not on my vessel.

Seven Step Radar Tuning.pdf (33.0 KB)

This tuning method is simple and works.
Note: The section on presentation modes is old, and does not include Furuno’s (and others, I assume) Head Up True Bearing mode, which is heading sensor (gyro or satellite compass) stabilized.


That’s exactly opposite of what I like to use. Barring operations in areas of multiple fixed objects relative trails is superior, at a glance it tells you which targets are danger targets without needing to duck around with an EBL. I prefer operating in true vectors as it shows own ship’s cog predictor, it’s easy enough to switch between true and relative vectors to see what your acquired targets are doing.

Yes, vectors should be true. Otherwise a very powerful feature of the radar is being used simply to "sort’ targets close CPA / “not close” but it’s doing it based on vessels current course/speed.

The vectors should be used instead to get an overview of what traffic is doing for example coastwise traffic rounding a point some vessel will sort close/not close by speed when in fact thay are all just rounding a point and none are going to be close. Same with ships following a VST lane, relative vectors of ships following a lane show no useful information. True vectors whould show which ones are flowing the lanes and which one are not.

With true vectors the display will also match the visual aspect of the vessel.