I use Google Earth images as a basis for my course maps with a method very similar to that Laurent posted. But I use TurboCAD Deluxe-10 software. That software is readily found at internet suppliers and will probably cost about $30. It has many features and options for preparing a drawing and does a good job for course maps. It is available in Windows and Mac formats.
I download the satellite image of the route and import that into the TurboCAD drawing as layer-1. I then add additional layers for the roads, primary features, text, and details as needed.
As Laurent does, I also exaggerate many features so the map is easier to read. This is important to clearly show the measured route.
I define roads using a double line, usually about 0.125" to 0.150" apart for the letter size page. And I typically use line widths of 0.01" for the roads and other map features and 0.02" for the measured route. Intersections can usually be formed by a couple of mouse clicks. Once all the major features are drawn, the Google image, layer-1, can be turned off. It is then easier to add road names, comments, notes, direction arrows and other information.
I normally save the drawings in the TurboCAD format, (.twc). File size is always less than 50 kb. Other formats are also available.
The following links show a few of these drawings on the RRTRC web site:
http://www.usatf.org/events/co...p?courseID=AL07016JD
http://www.usatf.org/events/co...p?courseID=AL08001JD
http://www.usatf.org/events/co...p?courseID=AL08023JD