deletions | additions       diff --git a/Methodology Video Data.tex b/Methodology Video Data.tex  index 7a0addc..a6abe7a 100644  --- a/Methodology Video Data.tex  +++ b/Methodology Video Data.tex 
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\subsubsection{Trajectories: Positions in Space and Time (x,y,t)}  Trajectories are a series of points in Cartesian space representing the position of (the center of) a moving object (road user) at time $t$ on a planar surface. Height $z$ is usually not considered. Points are evenly spaced in time with a consistent $\Delta t$ equivalent to the inverse of the framerate of the video, i.e. a measurement is done for each frame. Typical framerates for video are between 15 to 30 frames per second, providing 15 to 30 observations per moving object per second. The object (road user) itself is represented by a group of characteristic featureswhich are  spread over the object, closely spaced object  and moving in unison. Three potential sources of error exist: parallax, pixel resolution, and tracking errors. tracking:  \begin{itemize}  \item \textbf{Parallax error} is mitigated by maximising the subtending angle between the camera and the height of tracked objects. In practical terms this requires a high view or ideally a bird's eye view, tracking objects with a small height to base ratio. Passenger cars are generally more forgiving in this respect than trucks or pedestrians.