i.e. north, south, east, wrest - and anywhere in-between.

In (UK) English we talk about 'training' a spotlight on a target - usually meaning we follow the movement of the target on the ground; hence the idea that 'train' is in the horizontal plane (azimuth).

That said, there's no logical reason why a spotlight shouldn't be 'trained' on an aeroplane...

Websters:

train
4 a : proper arrangement or disposition : order designed or contrived to lead to some result *was already in fair train to develop party out of faction— Learned Hand* *the mathematics set in train by these two pledges will force a reduction of the total armed forces— New Statesman & Nation* b : a controlled or directed procedure : METHOD, PROCESS, WAY *things proceeded in this train for several days— T.L.Peacock* c : a line, course, or sequence of thoughts, actions, or events : an orderly succession : a connected series *the train of years sped swiftly by— W.F.Brown b. 1903* *his mind still upon his own train of thought— Agnes S. Turnbull* d : a set or progression of consequent or attendant events or conditions : a series of results or accompanying circumstances : AFTERMATH, SEQUEL *in the train of peace came industry and all the arts of life— T.B.Macaulay*