If you know me, you know I love Tracker Video Analysis. Basically, it is a free-java program that allows you to get position-time data of a moving object from a video. In Tracker version 3.10, there is now the autotracker feature. This will automagically mark the location of an object moving in a video. How do you use it?
First, the video. This is a video I made of a plane landing at an airport. Not much exciting going on, but that never stopped me before. I put this video on vimeo instead of youtube because vimeo allows you to download the original video.
Now what? Well, here is a short screen-cast tutorial on using the autotracker feature.
In order to scale the video, I used the size of the plane. That looks like a SouthWest Airline plane. I am pretty sure they only fly 737′s. According to Wikipedia, the 737 is 30.5 meters long. Really, that is the only thing I had to look up for this video.
How fast was the plane moving?
The aircraft is probably slowing down as it comes in for a landing. This means that the “how fast” question doesn’t have one answer. However, it it appears the acceleration isn’t too high. Here is a plot of the horizontal position vs. time for the plane with a linear fit.
The slope of this line has a magnitude of 76.4 m/s. This is about 170 mph. I guess that is an appropriate. I remember playing Microsoft Flight Simulator and that seems like an ok speed. What about the vertical speed?
1.5 m/s or 3.4 mph.
What is the horizontal acceleration of the plane?
Instead of fitting a linear equation to the horizontal data, I am going to fit a parabola. Doing this gives:
This equation is similar to the form:
Where the “a” term in this equation is the acceleration. This means the “a” from the fitting equation is 1/2 the acceleration. The horizontal acceleration of the plane is then 1.5 m/s2 or 0.15 g’s.