[Alpha Von Burg]

Bootsman's right, this is likely a radio contact report from other units.

Several nearby units intercept the radio transmission of the vessel in question and sends it to back to HQ, where they triangulate the source of the radio.

Otherwise, another friendly vessel reported a contact but could not engage.

Depending on the weather, max visibility is about 10-20 km (at clear weathers). To answer your question, your target is 100km from your current location. The (radio) contact marker which is displayed on you nav. map should indicate an approx. speed and general course of direction. This should be enough to plot and intercept course.

Cheers,