Coming back to my problem of not being able to receive GPS
info from the AIS
data stream (sorry for the delay).
I did some testing again on my system at the boat, connected the boat GPS and/or the AIS transponder through serial/USB converter cables
tried the version 3.1.1105 and here are my observations:
1. When I connect both instruments (boat GPS and AIS) all works well.
2. When I connect only the AIS transponder, then the following occur:
i. The LED indicator on the AIS transponder shows that it has found enough GPS satellites and receives/transmits all the required information including GPS. The transponder has its own GPS antenna
ii. The NMEA debug window (and opencpn
debugger plugin) shows that openCPN
receives sentences of the type !AISVDO, !AIVDM and $AITXT.
e.g. (approx.) !AIVDO,1,1,,,B3TEQ2,0000KODD44;kc9kw4kP06,0*3
and $AITXT ... internal_GNSS_in_use*3
iii. The Own Ship info in the AIS target list/target information window shows the correct latitude and longitude of the boat. These change correctly with the actual movement of the boat.
iv. The Own Boat icon remains gray and does not move on the screen
, the red dot at the NE corner of the screen
remains red and no satellite
signal srength is shown there.
v. The "NMEA events" window of the debugger pugIn shows only the last long/lat data, which it had received form the (external) GPS of the boat when it was connected at test #1, and indicates nSat=0.
I have to mention that I had noticed similar behaviour in a previous version of the software
, which was rectified in the version that followed. GPS info from AIS sentences was received and shared normally in my system in the last version (3.1.915), which did not show this problem.
For every test I chose the correct COMM port and baud rate - 38400 for the AIS transponder and 4800 for the boat GPS. The Accept filter field was left empty.
It seems to me, then, that GPS information is read by the program from the AIVDO (??) sentences, this info is used to update the AIS info of Own Ship and all other ships (in the AIS target info window), but perhaps it is not shared (forwarded) to be used in the calculation of the position of the boat on the screen. Could this be the reason?