Teulings, H.L., & Maarse, F.J. (1984). Digital recording and processing of handwriting movements. Human Movement Science, 3, 193-217.

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Hans-Leo TEULINGS and Frans J. MAARSE *
University of Nijmegen. The Netherlands

Methods of recording and processing handwriting movements by means of a computer-controlled digitizer are discussed. It is concluded that the presence of measurement ‘noise’ in the sampled movements makes it necessary to choose high sampling frequencies in combination with low-pass digital filters, especially if time derivatives have to be estimated. However, increasing the sampling frequency beyond some critical value does not improve the signal-to-quantization-noise ratio unless the raw samples are preprocessed by summing groups of samples. In order to correct for occasional nonsimultaneous sampling of the x- andy-coordinates a second type of preprocessing is required (linear interpolation). Subsequently, it is shown that low-pass filtering and differentiation can be carried out in the frequency domain, using FFT. if suitable extrapolation time functions and filter characteristics are chosen. Finally, various automatic procedures for the division of movement patterns into meaningful segments and a procedure for estimating the accuracy of the digitizer are proposed.