Comparison of three different ways of measuring distances between residences and high voltage power lines

The aim of this study was to evaluate whether distance data based on calculations by use of digitalized geographical information systems (GIS) and distance data based on measurements on 1:5000 maps agree sufficiently with on site distance measurements to be used as input to magnetic field calculations in epidemiological studies. The analysis were performed by use of weighted kappa (kappa(w)) statistical method described by Bland and Altman for comparison of measures of agreement. Map measurements showed better agreement with on site measurements than GIS calculations did. However, we consider both methods appropriate for use in larger epidemiological studies if the results are interpreted with caution. GIS calculations have the advantage of being both time and cost saving.