[Eclipsemullet]

I have got our NASA AIS working okay but a lot of the ships are showing as '???'.

What does that signify?

[GPSNavX]

It means the vessel's name has not been received by your single channel AIS receiver. Read up on the frequency of the timing and availability of AIS data here..

http://www.navcen.uscg.gov/enav/ais/what...dcasts.htm

Static information such as vessel name does not update as frequently as dynamic real time data such as speed and course.

[Eclipsemullet]

So, would I be right in thinking that the NASA engine is a Class A receiever?

http://www.navcen.uscg.gov/enav/ais/types_of_AIS.htm