[PUP] AIS pitfalls

[Dave Cooper]

<John wrote: I'm used to seeing a projected course track that extends
outward from  the target, the distance proportional to the ship's speed.>

I believe that the projected arrow is from the course info and the ship's
symbol is from the heading info. So if they are not in "approximate"
agreement then you can have two conflicting pieces of information display.
Then it becomes as matter of "which is correct?"

If the ships gyro aka heading input to the AIS box is in error due to being
wired incorrectly or some other issue then they won't even closely agree.
The AIS GPS gives the course, the gyro or whatever is used gives the
heading. A boat making with a heading of 90 degrees with show the ship
oriented in this direction from the heading input however if it is drifting
south then the projection line will be in this direction from the GPS.

So the installation and the frequent check on the transmitted data is
required. I would think that the system would be required to show on another
display your transmitted information....easy cross check and would help to
insure that you have inputted the correct data and that the black boxes
feeding the AIS are doing so correctly. Without this what do you have??

As always YMMV

Cheers
Dave & Nancy
Swan Song
Roughwater 58
Caribbean Cruise '07