1. A method of generating, revising, or extending a digital map, said digital map storing a plurality of line segments or features spatially associated within a coordinate system representing a network within a geographical area, comprising: providing a plurality of probe traces extending across a geographical area; dividing the probe traces into a plurality of sub-sets, wherein each sub-set includes a plurality of probe traces having at least one criteria in common; employing probe traces of a first sub-set using a first processing thread to generate a first sub-network of line segments; employing probe traces of a second sub-set using a second processing thread, while the first processing thread is employing the traces of the first sub-set, to generate a second subnetwork of line segments; and conflating at least said first and second sub-networks of line segments to generate a network of line segments associated with the geographical area.