3D GIS for surface modelling of magnetic fields generated by overhead power lines and their validation in a complex urban area.

Residential exposure to magnetic fields generated by overhead high-voltage power lines, continues to be a matter of social concern and, for the scientific community, a challenge to model this exposure accurately enough to reliably detect even small effects in large populations complexes. In any expression of the magnetic field intensity, the source-receiver distance is a determining variable, especially in an environment closer to the electrical installation and critical with the existence of significant unevenness in the terrain. However, MF exposure studies adopt, due to their complexity, simplifications of reality where even sometimes the terrain relief and the buckling of the line are not considered. The application of 3D techniques with Geographic Information Systems (GIS) allows us to address this problem. This article presents a model for generating magnetic field intensity surfaces from high-precision terrain elevation data. The series expansion of the Biot-Savart law to an infinite rectilinear conductor with variable height according to the catenary described by the cables using ArcGIS software is applied to calculate the magnetic field. For the validation, 69 control points (1035 field measurements) were used in a free urban area and another 28 points (420 field measurements) in a built-up urban area with complex relief. Good estimates were obtained, although with differences in both areas. With MAPE 9.65% and 19.51%, R2 = 0.922 and 0.949, RMSE = 0.154 and 0.094 μT, respectively. Furthermore, 86% of the points were correctly classified according to usual exposure percentiles. However, the use of a 5 m resolution digital terrain model to obtain high-precision elevation data was an indispensable condition for the good performance of our model. The result as a continuous surface of magnetic field values at the real elevation of the ground can contribute significantly to the development of new environmental and public health studies.