The reason for stating the heading is so that the controller can follow the method of primary radar identification with a minimum of calls. The procedure is:
1. Pilot reports heading
2. After a period of assesment, pilot is instructed to make a turn of 30 degrees or more.
3. Provided that only one aircraft responds to the instruction, the aircraft is identified.
Thus by reporting the heading on initial call, step 1 above is completed.
In the SSR environment however, none of the above is required.
However, the R/T manual tries to use generic catch all calls whenever possible......after all as a pilot on handover has no way of knowing that the controller's SSR failed 2 minutes ago.
It is true that radar displays track.....this must be remembered when the controller points out traffic "12 O'Clock" when you are tracking along with a 20 degree crab angle!!
Regards,
DFC