I can only guess, but it seems to me that the devs have atried to simulate - to a certain extent - the situation as it was. Contacts came from:
a) the sub itself, via, hydrophones, sonar, radar, or lookouts.
b) outside reports ( i.e. ComSubPac).
They received reports from air reconnaissance units ( + other air units ) surface ships, other submarines, coast-watchers and Radio DF triangulation. All these reports and more were processed and transmitted to patrolling US submarines.
That's what's appearing on your Nav map - a combination of all the available reports. I think they "filter" single-ship reports to those they believe you may be in a position to attack.
Don't forget, ComSubPac only knows where you're headed ( mission objective ) and probably where you should roughly be on an optimum course to get there, but,essentially, your actual whereabouts are unknown to them.
After Pearl Harbour, the U.S. was understandably paranoid about being caught out again and put massive effort into reconnaissance and target finding.
|