By human measurements, the distance was about 7m at about 45° (i.e NE). GPS says 8.6m, video camera tracking says 5 which is the flight plan defined length to travel.
It was never going to be perfect due to the difference between magnetic and true north, the resolution of GPS of around 1m, and how video distance tracking will always be a best guess, but it’s more than good enough for my cunning plan to work.
However, the plan’s taking a premature diversion; during this test, I was less careful and she ended up (in vertical descent mode) clipping 5 props against the drive stone wall. Next step (after replacing the props!) is now to deploy my Scanse Sweep code which will trigger an orderly landing if any object is detected less than 1.5m away – Hermione’s radius is 50cm prop tip to tip diagonally so that’s 1m clearance.
One interesting point: the compass readings are mostly in a very dense cluster, with just a few (relatively) pointing in very different directions – that’s as Hermione passed the family car!