In a radar environment, what should be considered as the runway centerline for a helicopter departure?

When considering the runway centerline for a helicopter departure in a radar environment, the helicopter takeoff course is the most appropriate reference. This is because the takeoff course accurately reflects the path along which the helicopter is intended to ascend and depart from the helipad or runway area. Unlike fixed-wing aircraft that rely on a traditional runway centerline, helicopters can take off and land in a more vertical manner and in a wider variety of positions.

The other options do not accurately represent the runway centerline for a helicopter departure. The helipad center focuses solely on the landing pad location rather than the flight path, while designating distances from another aircraft's runway centerline does not establish the helicopter's actual takeoff trajectory. The unique nature of helicopter operations requires a focus on the specific course taken during departure, rather than fixed measurements relating to other aircraft.