Ya know... I'm looking at that example again, and I don't know what to tell ya; it just looks like the OP is wrong.
Based on the bearings and distances stated, the contact moved over 3300 meters (2 miles) in just 3 minutes? There's just no way you'd get a 4kt speed (relative motion) from that...
I dunno, maybe I'm doing something wrong.
I should go get Lurker to take a look...