Distance Matrix is the matrix of distances between stations in a station set. The
distances can be real geographic distances between station coordinates or crow fly
distances (i.e. direct distances over earth).
Road Distance Matrix is the distance matrix in which the values are retrieved from
underlying GIS system automatically as real world distances according to minimum
road network map. Therefore, the values in Road Distance Matrix reflects the real
distances from one station to another station by traveling on the road network.
Crow Fly Distance (CFD) Matrix is the distance matrix in which the values are retrieved from underlying GIS system automatically as minimum distances over earth surface without traveling on road network. Therefore, the values in CFD are not the actual world travel distances by road network. It can be considered as a minimum flight distance matrix.