I couldn't resist playing around some more with the recent video purporting to be a recording of an Emirates A380 departing MRU in Mauritius. There has been much debate online, including an earlier thread on this forum about whether this was real or fake. It turns out that quite a lot of information can be extracted from the video.
Firstly, and rather trivially, as I posted in the other thread, the motion of the aircraft past fixed locations in the distant background can be used to determine speed given the known length of the aircraft (73 m) and the frame rate/timestamp of the video. The video reports as 24 fps and the aircraft travels its own length past the viewing location in approximately 24.5 frames. The images below are 25 frames apart.
That gives a ground speed of 71.5 m/s, or 140 kn. While that's slower than V2 (the climb out airspeed) for the A380, which is 150 - 160 kn, it was almost certainly taking off into a headwind, and so that's a very credible ground speed.
Looking at the earlier part of the video, and plotting sights lines as the viewpoint rotates, one can triangulate on the position of the view point. It turns out that appears to move towards the runway centerline as the video progresses, which is consistent with the visible drift in the video.
That indicates that the viewpoint was 1880 m from the end of the runway, and 2630 m from the V2 point. Timing the aircraft from the V2 point to the viewing location gives an average speed of 71 m/s - in very close agreement with the previous estimate.
In terms of altitude, the A380 would likely be climbing at around 10 - 12°, which is consistent with its measured attitude. That would put it at around 470 m MSL passing the view point. The view is looking down slightly at the aircraft, putting the viewpoint at around 490 MSL - just under the hard FW ceiling for a DJI drone.
We can play a couple of other tricks with the video images. In the image below, the apparent lengths of the near wingtip is almost exactly twice that of the far one. That implies that the far one is twice the distance from the lens as the near one. Given that the wing span of the A380 is 80 m, that puts the viewpoint 120 m from the center line of the fuselage, or 80 m from the near wing tip. By comparing the apparent length of the aircraft with the full width of the image and with the 120 m value for distance, we can calculate the horizontal field of view of the lens, which comes to approximately 57°. Interestingly, that is exactly the horizontal FOV of the Mavic camera.
Putting this together allows the construction of a 3-D representation of the depicted event in Google Earth:
Overview (load first): Dropbox - Overview2.kml
Viewpoint perspective: Dropbox - Aircraft_view05.kml
Other notable points:
Firstly, and rather trivially, as I posted in the other thread, the motion of the aircraft past fixed locations in the distant background can be used to determine speed given the known length of the aircraft (73 m) and the frame rate/timestamp of the video. The video reports as 24 fps and the aircraft travels its own length past the viewing location in approximately 24.5 frames. The images below are 25 frames apart.
That gives a ground speed of 71.5 m/s, or 140 kn. While that's slower than V2 (the climb out airspeed) for the A380, which is 150 - 160 kn, it was almost certainly taking off into a headwind, and so that's a very credible ground speed.
Looking at the earlier part of the video, and plotting sights lines as the viewpoint rotates, one can triangulate on the position of the view point. It turns out that appears to move towards the runway centerline as the video progresses, which is consistent with the visible drift in the video.
That indicates that the viewpoint was 1880 m from the end of the runway, and 2630 m from the V2 point. Timing the aircraft from the V2 point to the viewing location gives an average speed of 71 m/s - in very close agreement with the previous estimate.
In terms of altitude, the A380 would likely be climbing at around 10 - 12°, which is consistent with its measured attitude. That would put it at around 470 m MSL passing the view point. The view is looking down slightly at the aircraft, putting the viewpoint at around 490 MSL - just under the hard FW ceiling for a DJI drone.
We can play a couple of other tricks with the video images. In the image below, the apparent lengths of the near wingtip is almost exactly twice that of the far one. That implies that the far one is twice the distance from the lens as the near one. Given that the wing span of the A380 is 80 m, that puts the viewpoint 120 m from the center line of the fuselage, or 80 m from the near wing tip. By comparing the apparent length of the aircraft with the full width of the image and with the 120 m value for distance, we can calculate the horizontal field of view of the lens, which comes to approximately 57°. Interestingly, that is exactly the horizontal FOV of the Mavic camera.
Putting this together allows the construction of a 3-D representation of the depicted event in Google Earth:
Overview (load first): Dropbox - Overview2.kml
Viewpoint perspective: Dropbox - Aircraft_view05.kml
Other notable points:
- It's hard to see without running the frames slowly, but the image distortion due to exhaust gases is actually visible. As the aircraft passes against the background of the shore line it's particularly noticeable.
- This flight has to be EK702, with a scheduled departure time or 1635. The flight that appears to have just landed appears to be another Emirates A380, which would make it EK703, with a schedule arrival time of 1630. That's consistent too, although both are rarely on time. However, looking at historical data for July, there are two possible dates: on 7/16 EK703 landed at 1632 and EK702 took off at 1637, while on 7/17 EK703 landed at 1633 and EK 702 took off at 1637.
- The reflection of sunlight on the fuselage raised a number of questions given the apparent cloudiness. However, it's apparent that the aircraft produces a clear shadow on the runway, and so there is at least weak sunlight. On the dates and times mentioned above, the sun azimuth was 299° with an elevation of 14°. That puts it almost directly back down the runway as seen from the viewpoint, and so the observed reflection is geometrically consistent with the sun location.