Short services

The short serve starts badminton rallies and puts the server on the offense straight away.  In doubles,  it is the prima optis, or first choice.  This may not be news, but recently I noticed something.  After watching a number of international matches, including the one below I spotted a pattern.
The picture below is a snapshot taken at 10:18 in the bwf youtube posting of the match.  Ahsan has just served to Hong and Hong is at the moment of striking the shuttle.  Notice that the shuttle is going to be struck approximately midway between the net and the service line.  The distance between the net and the service line is 1.98m.  That means that the shuttle is being struck approximately 1m from the net.  I have observed this in a number of international matches.
The significance of this is that the service receiver requires that the shuttle be close in height to the net in order to make an effective short return.  The traditional advice is to keep the service low as it passes the net.
Imagine a horizontal rectangle formed by the net, an imaginary line 1m from the net and two lines parallel to the centre line and the sideline.  Imagine that this rectangle forms the opening of the top of a box or a large horizontal letterbox.  In many respects, the most effective serve is one that passes over the net (obviously) and is as low as possible when it is 1m from the net and lands on or beyond the service line. 

In practice, I have noticed that the best trajectory of short serves is not necessarily one where the shuttles passes close to the net.  I think that this is significant.

FINAL -- MD -- M. Ahsan / H. Setiawan vs. Chai B. / Hong W. -- 2013 Yonex Open Japan.

 Please refer to this link for more information.
A study of shuttlecock’s trajectory in badminton