Accuracy Assessment of Digitized Data with Randomized Block Model

This study uses randomized block model variance analysis to assess factors affecting the quality of digitized data yielded by a digitizing tablet and desktop scanner. First, the geometric accuracy of a digitizing tablet and desktop scanner and the spectral response of the scanner were examined using a “calibration” reseau and a commercially available grayscale. The average planimetric positional error (μ_p) for the digitizer and the scanner were 0.249 and 0.119 mm, respectively. Experimental results showed that the planimetric position root mean square errors of both devices satisfy map accuracy requirements, and that scanner gray level response was homogeneous. Furthermore, this study used randomized block model variance analysis to assess factors affecting the quality of digitized data yielded by a digitizing tablet and desktop scanner. The effects of digitizing procedures for both devices were evaluated by this analysis. The ANOVA tables indicated that different map positions and widths of lines for a digitizing tablet, and the operator and scanner density for a scanner are shown to important elements in the data acquisition process.