OBJECTIVE: The purpose of this study was to assess whether distance data based on calculations by use of 2D and 3D Geographical information systems (GIS) and distance data based on measurements on 1:5000 maps accord with on site distance measurements to use input data for calculating magnetic field. 

METHODS: On site measurements were performed by use of Ultralite LR(Ultratech) laser meter. One hundred eight of the on site measured addresses were selected from residences in and around Jung gok-4 dong, Seoul. The data were achieved by measuring the distance between residence and power line on maps with scales of 1:5000. The digital map was obtained from National Geographic Information Institute with scales of 1:5000, and we made 2D and 3D map by using with Auto CAD Map2000i and Arc Map 8.3 simulator. We divide the addresses into three magnetic field exposure categories, based on typical load and configurations for different power line voltages. The correlation analyses were performed for statistical analyses.

RESULTS AND DISCUSSIONS: For the 3D GIS versus on site comparison of different exposure categories, 70 of 108 measurements were assigned to the correct category. Similarly for 2D GIS versus on site comparison, 71 of 108 were correctly categorized. When comparing map measurement with on site measurement, 62 of 108 were correctly categorized. When the correlation analysis was performed, best correlation was found between 3D GIS and on site measurements with r = 0.84947 (p<0.0001). The correlation between map and on site measurement yielded an r of 0.76517 (p<0.0001). Since the GIS measurements and map measurement were made from the center point in the building and the on site measurements had to be made from the closest wall on the building, this might introduce and additional error in urban areas (Blaasaas; 2002). The difference between 2D and 3D calculations were resulted from the height of buildings. 

FUNDING AGENCY: This research work was supported by ECO-21 Research Grant No. 2004-09001-0038-0 from the Korea Ministry of Environment (2004~2005).
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