Download and start Google-O by clicking on the above link
In GoogleEarth, click on the link named Map found under the folder named Google-O to display the map in the Goggle Earth browser window below the GoogleEarth window.
Navigate Google Earth and place the green crosshair over the start placemark. A yellow dot is shown and the timing is started.
Note: you have to stop completely at start and every checkpoint for registration
Place the crosshair on the spot where you think the next checkpoint is. If you hit the right spot, a yellow dot should appear. If not, then you have not found the right spot. Try again.
Continue the procedure until the finish. Here your final time will be displayed in a message box.
Start Google-O again by placing the crosshair over the start placemark.