On Thu, 17 Aug 2017 23:55:48 +0100, just as I was about to take a
herb, Brian Reay disturbed my reverie and wrote:

The idea does have its merits. With a bit of ingenuity, you could
arrange a 'station keeping' control using GPS and possible some sensors

When I was recently on holiday, some tool was flying one of these over
a crowded beach. It did seem to have a "stay put" feature as it would
hover in position so well, that I doubt that it was under manual
control.
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73 de Guy G4DWV/4X1LT