Each marathon is unique. Unlike the uniform tracks designed for short-distance races, marathon routes wind along streets, and rise and fall with the local topography. Some are more linear, while others twist and turn. Depending on the orientations of the segments, a runner can complete the race and end up back at the start line, or close to 26.2 miles away. Clearly, the former scenario is more convenient for participants who drive themselves to the race. Marathon spectators may also prefer loop-shaped courses, allowing them to view the excitement of the start and finish without much effort. This graphic analyzes five of the world’s major marathons, binning the segments of the race by direction traveled. More symmetric rose diagrams, like those of Berlin and Chicago, result from loops. Those that are strongly asymmetric, particularly Boston, are indicative of a linear route with the start and finish lines located far apart.

To generate the graphics, a shapefile of each marathon course was mapped using ArcGIS. The maps are equally scaled to allow readers to compare the courses directly. The polylines for each route were then broken into 13,110 equal-length segments (500 segments = 1 mile). The azimuths of the segments were calculated and then plotted on rose diagrams using R. In the polar coordinate system, the distance run is represented by the radial length of each bar; the diagrams are equally scaled, with each concentric circle equal to two miles. Summing the vectors for a given course yields a vector that points from the start line to the finish line, and has a length that is equal to the distance between them.

Data sources (for street backgrounds):

http://www.census.gov/cgi-bin/geo/shapefiles2013/layers.cgi

http://download.geofabrik.de/