deletions | additions       diff --git a/Methodology Video Data.tex b/Methodology Video Data.tex  index 5acac30..fc15648 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, at the simplest level, a series of points in cartesian space representing the position of (the center of) a moving object 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. Typical framerates for video are between 15 to 30 frames per second, providing 15 to 30 observations per moving object per second. The object itself is represented by a mass of characteristic features closely spaced and moving in unison. Feature grouping is handle  Three potential sources of error exist: paralax, pixel resolution, and tracking errors. Paralax error \begin{itemize}  \item \textbf{Paralax 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. Pixel resolution \item \textbf{Pixel resolution}  determines measurement precision. Objects further away from the camera experience lower tracking precision than objects near the camera. Error due to pixel resolution is mitigated by placing study areas nearer to the camera and  using high-resolution cameras and observing objects near the camera, cameras,  although increases in resolution offer diminishing returns of tracking precision. distance.   \item  Finally, tracking errors \textbf{tracking errors}  may occur with scene visibility issues or due to limits with current computer vision techniques. These erroneous observations have to be rejected. rejected or reviewed manually.  [CITE] \end{itemize}  Depending on the steps taken to minimise tracking areas, video-based feature tracking functions best over study areas of 50-100m in length with high-to-medium speed, low-to-medium density flows.  \subsubsection{Derived Data: Velocity & Acceleration}