What are the seemingly random single ships i can spot from 500+km range?

[TheBadCaptainOfAU-Boot]

Timewarping through the seven seas, my game goes to 8x speed randomly because there is an enemy ship 300km from me? How can i know that this ship is here, traveling to this direction at this speed when i don't receive a radio report, just a random spot appears on the map? What are these boring lone merchants which just randomly appear about 100-500km away from you without any backstory how i know they're there?

[Obltn Strand]

Your radio man used this:https://uboat.net/articles/id/51

[David I]

Bad Captain,

They are radio intercepts either from your own direction finder or BDU intercepts of single ships (some times it's one ship, sometimes more) sending position reports or requesting course information.

They are there alright. Get their course and draw a line on the map and plot a interception route. When you get to the point where you think you might be fairly close submerge at low speed and pick them up on your sonar. They may be little off from what you plotted. Then try to get a periscope fix on it (them) and draw a line on their true course. Then go get'em.

I get far more kills that way than just blundering into a single ships.

Good Hunting,
David I

[Pisces]

When clicking on the icon you get a time when they were there, a generic speed-range (there are config files that tell you how fast this is, iirc. contacts.cfg ) and rough course (N, NNE,NE, ENE, E, etc.) From that spot draw a line along the course of 170km length. Draw a circle of 34km radius at the end of it. Now, create an ice-cone out of it. Make sure you can intercept within that region before they move to the end of the 170km. Then you get to eat it. ;) If not, the area of uncertainty where they can be grows beyond your hydrophone range. Better be there as soon as possible as they can make a course change before that.

[Anvar1061]

Intelligence data.