Snap multiple markers to the nearest road

I have a list of GPS points with which I create a path on a map according to the tutorial http://wptrafficanalyzer.in/blog/route-between-two-locations-with-waypoints-in-google-map-android-api- v2 / . I would like to put these points as markers on the map so that it is a road. I am interested in determining where the closest point of the drawn path is relative to the point where I have the GPS. How to do this without forcing every point of the new request to refer to the google directions api.