In the world of survey management, we sometimes need to determine distances between addresses.  Perhaps we are trying to establish which study subject persons are within a specific distance of an interviewer.  Maybe we want to identify existing establishments such as doctors’ offices, hospitals, clinics, or pharmacies that are a reasonable distance from our study subjects. Such distances are often measured in absolute terms; such as all of the doctor offices within 50 miles of a subject. But, straight-line, as-the-crow-flies, distances do not account for geographical and infrastructure features such as mountains, rivers, lakes, and existing highways and surface roads.  Consequently, driving distances may be more reliable than absolute distances.

When many of us want to get from Here to There, we invoke Google Maps, plug in the address for Here, plug in the address for There, and hit ENTER.  Google Maps then returns some routes to our destination…