Winter Wondering

Worth reminding yourself of yesterday’s down-facing Mavic video of the flight first.

This graph is made from the raw GPS data from the NEO-M8T – no processing by me other than saving the results to file:

GPS waypoints and flight

GPS waypoints and flight

The grey line is the 3 preset waypoints: orange, red and purple correspond to the same coloured frisbees you can see in the down-facing video from yesterday.  The GPS waypoints on the graph are a very plausible match with their places in the video, both in location of each and the distance and direction between them .

The blue line is Hermione recorded live as she flew to the orange waypoint.

Here are the problems:

  1. Hermione took off from the purple frisbee in real life.  As she took off, she determined her GPS takeoff point dynamically.  This GPS point in the graph is about 4m away from purple waypoint(s) on the graph.
  2. In the video, you can see she flew in the right direction towards and beyond the orange frisbee.  In contrast, she thought from her GPS tracking that she was only ½ way to the orange waypoint, hence the real-world overshoot, and my termination of the flight.
  3. Hermione was travelling at 1m/s and the video back this up.  However the intermediate GPS locations she read suggest more like 0.3m/s based on the fact GPS updates happen at 1Hz.

Both for presetting the waypoints, and during the flight itself, 9 satellites were in use.

While the difference in take-off location of 4m is just about tolerable as a fixed offset, the fact the GPS points suggest 0.3m/s (compared with the real, correct 1m/s) is not and I have absolutely no idea why the NEO-M8T is doing this.

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