# What the GP(S) saw

Hermione did two 2m straight line flights today, and both landed about 3.1m away measured manually with a tape-measure.  The stats from both flights showed Hermione thought she’d flow just the 2m:

2m from video POV

So there’s a scale of 1.55 x real distance = down-facing-video distance that needs fixing.  The scale formula I used to convert the video macroblocks to meters was an informed guess, and it may just be missing a π/2.

The 2m square flight plan I flew and plotted the other day is actually a 1.8m square (0.3m/s for 6s) when I checked the flight plan earlier.  After applying the video tracking error scale of 1.55, this is the comparison of the rescaled flight plan against what GPS saw.

GPS vs. virtual reality

The square is about 3.95m diagonally, and the errors between this and the GPS plot seem to be ≈±0.75m.  Horizontally readings are about 1m apart whereas vertically, it’s more like 0.75m – not sure yet whether that’s how it works out due to our latitude, or if there’s a bug in my GPS processing.

What’s this all mean? First, I need to add a factor of 1.55 to the video, and second, GPS directed flights could be made to work after all if

1. obstacles surrounding Hermione are at least a meter away, probably two
2. destinations are several meters away, best guess is 5 meters or more.
3. sweep gets turning back on!

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