Extrapolating a from location and to location from given latitudes and Longitudes

I have line segments and points feature data collected using GPS. The latitude and longitute points forthese features werecollected without any "from location" and "to location" information. How can the "from location" and "to location" information be extracted from the latitude and longitude information, if that is possible. The "from location" and "to location" values are needed for creating route events in linear referencing.
I would appreciate any help or suggestions offered

Thanks, Ron