In this screenshot the contact "SKUNK #4" is unknown, but when you check the "Contact report" there is only one possibility based on the emissions detected.
Why is the contact "unknown" when there is only one possibility?
It would be great if there were a it more information available for "Unknown" contacts. Even with a cheap and very basic commercial radar you can tell the difference of an echo from a super tanker and a small recreational boat. And an experienced user could make very good educated guesses based on the echo strength/size and it's distance.
So perhaps some info along those lines could be provided for unknown contacts?
