I have been using a handheld GPS for a few years. Before measuring a new course, I load the course plot onto my Garmin GPSMAP 60cx. Then, while riding in my car or on my bicycle, I can follow the path on the GPS, locate upcoming turns, and even look ahead to see which way the road curves.
My GPS came in handy while measuring at night. A few weeks ago, Ray Nelson and I remeasured the Boston Marathon course. We started at midnight and I rode behind Ray. Using the GPS as an odometer, I was able to announce the upcoming mile and kilometer splits which were painted in blue on the road. The GPS was accurate to one-hundredth of a mile for most of the ride. The tall buildings, however, scattered the satellite signal as we were going through Boston.
The latest version of Google Earth does allow you to view elevation profiles. Take a look at this article:Google Earth does Elevation Profiles
Thank you. -- Justin