I have spoked to cruising hams that report their position over APRS using their HF radios and their SCS Pactor modems.
The software they use is
http://aprsisce.wikidot.com/ APRSISCE and it is windows software but the web sit says it works under wine.
They say they can also use the Robust Packet Network to connect to APRS. If you look on the
http://robust-packet.net/ RPN website you can see a couple of yachts that have used the system in the last few days in Europe. Bob Smith says (on the Facebook group Offshore SSB Radio and Email) he sent 10MHz APRS/RPN position reports all through the night at sea.
So has anyone tried APRSISCE under WIne on Navigatrix? Or is there native Linux software that does the same. Or are you hard-core and just open up a terminal and send commands to the modem directly (mine does APRS automatically that way)