A method of creating an obstacle-free diagram using topological sensor data to form a graph corresponding to a driving path, transforming the graph using discrete heuristics, locally smoothing a plurality of edges of the graph after the transforming, and globally smoothing the graph after the locally smoothing. Transforming includes deleting an edge of the graph, merging two intersections of the graph into a single intersection, and collapsing a plurality of edges forming a loop into a single edge. Locally smoothing includes smoothing a lane segment of the graph by minimizing a sum of a function of smoothness and a function of distance. Globally smoothing includes defining an intersection potential and minimizing a sum of the function of smoothness, the function of distance, a function of intersections and a function of direction.