1. A computer-implemented method comprising: obtaining, by one or more computing devices, plural pixels corresponding to satellite imagery of a region; calculating, by the one or more computing devices, for each of the plural pixels, a probability value corresponding to the probability that the pixel belongs within a road network; forming, by the one or more computing devices, an image based on the calculated probability values; producing, by the one or more computing devices, plural curves based on the image; and generating, by the one or more computing devices, a planar-connected graph by connecting at least portions of the plural curves, wherein the planar-connected graph corresponds to the road network.