Thoughts on Laube et al (2011)

I have never before considered the complexity of measuring movement. A significant portion of the authors’ work seemed to be dealing with the issue of positional accuracy of a GPS transmitter. Since the data being collected is so simple in form (tuples containing id, x, y, timestamp), all subsequent calculations are determined by the changes in the x and y-coordinates, assuming data is collected at precise intervals. The techniques used in this study, in particular the explicit definition of segmentation values and their influence on trajectories, are only relevant when the data consists of these three dimensions (euclidean position and time).

Technology has advanced to the point where temporal GPS data can be supplemented with local measurements. Accelerometers record local movement, and could be used to simplify data manipulation in the lab. The “rules” defining movement trajectories and stationary segments can be incorporated into a GPS receiver/accelerometer device. Rather than “pruning” subtrajectories in short time intervals or small distances, location data might only be recorded when local movement has been measured to be over a threshold distance from the last recorded location. Accelerometers might also be able to help “smooth” trajectories by vectorizing movement at one recorded location to lessen uncertainty of the next recorded location.

Using a dynamic temporal scale, where location data is supplemented by acceleration vectors, might make most of this research irrelevant.

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