"Lynn Coffelt" wrote in
:

Is AIS used on relatively unmovable objects such as rocks and
small
islands? There are quite a few radar beacons in use, but some radar
receiver interference rejection schemes wipe them off the screen too.
(I almost said "scope", nearly revealing my age!)


Radar requires the target to be REFLECTIVE, not absorptive or transparent
to RF. That's what that funny ball hanging from the already reflective
metal mast is, it makes you more reflective. A wet, plastic boat with an
RF absorptive human isn't going to cut it. The seawater returns more
than that....

As to your AIS barb...YES! But, your concept of AIS being located on a
bouy is all wet, so to speak. AIS has no bearing on it being mounted ON
the object it reports. That transmitter can be anywhere, as long as it
is in VHF range of the receivers. Fixed objects and Notice to Mariners
objects only need one, central transmitter high enough to cover the
entire area. This transmitter broadcasts the data of all these objects
every X minutes, to the delight of every AIS-equipped boat in range.
That range can be substantial. The sooner this equipment is installed
and the CG forced, kicking and screaming, to maintain its database with
all the latest data, the better!

For instance, a report comes in from the "Lady Disaster" that there is a
new object gone aground on "Monster Bank" at X lat/Y long, and represents
a hazard to navigation. The broadcast noone listens to goes out on
Channel 22 and falls on deaf ears. Admit it, you don't listen to it when
you're out, do you? I thought not. Who the hell's got time to plot
these broadcasts? However, the duty watch at the CG base also enters the
new object into the AIS database the fixed area transmitter draws its
data from. The very next transmission cycle, the new object shows up on
ever AIS display/chartplotter within 50 miles of the TV tower the
transmitter is located on. You can easily see the new obstruction. It's
right there on your display at the helm.

The bouy tender has arrived to assess the situation at "Jim Island" found
to be shifting into the channel. Bouy 4C is nearly sitting on dry land
because of the current shift and they lift it out and service its
batteries, replacing a bad bulb in the bulb rack in the head. They
replace the bouy in a new position further out in the channel than it was
to mark a safe distance from the new beach Jim Island is building for the
kids to play on next spring. Job completed, the duty radioman pops up
his AIS update screen on the ship's computer and logs onto the local AIS
database, right from Jim Island. He pops up Bouy 4C's record and enters
the new lat/long of its new position, making a note on its comment
section of the building beach to warn AIS-equipped boats to be wary as it
is still building. INSTANTLY, on the next transmission 86 seconds later,
every AIS-equipped boat notices 4C move to its new location and can read
that comment if they click up the bouy on their AIS-enabled chartplotter.

How long would it currently take to note 4C has moved 300 yards into the
channel, or a new warning come out from any authority now in use? Weeks?
Months? 12 days after the damned bouy has to be moved again?!

The sooner the better. There is NO TRANSMITTER ON ANY BOUY on an AIS
system! Totally unnecessary. There needs to be a central database and
high transmitter to cover the whole area on the AIS system... AIS is
about DATA, not direction finding.

Larry
--
Wow. Halloween candy has gotten cheap, lately!