As far as I can tell, everything is coded properly. We did our best to test it and haven't seen major deviations in the latest versions.
Just remember, that the convoy may change its direction, as it's not travelling on a straight line from port A to B. It may also be attacked by other u-boats, which may also affect what you hear. To counteract such problems, try to make multiple measurements as you approach it rather than to count on limited data points. Hope it helps
