Creating a GPS cycle route on Google Earth
You can plan any type of route on Google Earth – not just a cycle route – but in my case I'd like to plan the route for a cycle tour in Denmark next May. Denmark has a network of cycle routes, some of which run alongside roads, but some follow country tracks that aren't all marked on Google Maps or other online mapping systems like OpenStreetMap. The advantage of Google Earth is that you can actually see the cycle routes and the sort of terrain they pass through. The way I'm doing it is to draw a 'path' by clicking a succession of points along where we'd like to cycle.
You draw a path on Google Earth by clicking the 'Draw Path' button on the toolbar above the map – see the pink oval at the top of the image above. This opens a dialog box into which you can type the name of your route and select a colour and line thickness. It also converts the hand symbol to a square cursor. You can drag this cursor along the map, laying down a track of points, but it's probably better to create the route by clicking, otherwise there will be too many needless points when the route is stored on a GPS. In fact, on the GPS unit (mine is a Garmin eTrex Legend HCx), the route will be stored as a track, not a route, because more trackpoints can be stored than routepoints. My route is the blue line on the map (example only). Once you've finished drawing your Google Earth path, you close the New Path dialog box, save the path, then email it to yourself before you close the program. This process is illustrated in the second image (inset), which shows the Google Earth sidebar menu. You will receive a .kmz file in your email inbox, in my case called Cycle path.kmz.
As an alternative to emailing the path to yourself you can save it from Google Earth to your hard drive with File / Save / Save Place As (illustrated).
Either way, the .kmz file then has to be converted to a .gpx file suitable for a GPS. Use RouteConverter. It works well, and gives you the option to convert with 'save as route, track, and waypoint list' as well as providing several map options in the map window. RouteConverter actually allows you to plan a route in Google Earth view too, but doesn't display all your position markers at once, as Google Earth does (the little red or blue squares on the map above). Converting .kmz files to GPS-friendly .gpx format can also be done online at GPSies.
Following the route with a GPS
The Garmin eTrex Legend HCx allows a maximum of 250 routepoints in a 'route' you can navigate, and 500 trackpoints on a 'track' you can follow. 'Navigate' is when you set the GPS to guide you along a thick purple line with directions. You can also navigate a track using 'tracback' – a bit fiddly in my experience, but in any case I don't want to navigate as such. On a cycle tour you want to conserve your GPS batteries as the unit will be switched on for most of the day and there isn't always somewhere to recharge the batteries. 'Following' a track uses less power. All you do is select your track and follow the trackline on the GPS map (see example, right).
Preparing the track in Google Earth
For a multi-day cycle tour you'll probably prepare a separate track for each day. That means 500 trackpoints maximum per day. The eTrex Legend HCx can store 10,000 trackpoints internally – enough for 20 days.
Following the track essentially means following the path you created in Google Earth. It will be a series of straight lines between the places you clicked on, so it won't necessarily be directly on the actual road or cycle route at all times, as you will be. So you need to make sure that when you create your path, it will be close enough to indicate that you're going the right way when you compare your position on the GPS map with the trackline. The 500 trackpoints your have at your disposal per day are normally enough for a whole day's cycling.
To 'fly the route' in Google Earth, there's a Play Tour icon button at the bottom right of the Places box in the sidebar. View a 'fly by' example here (the Nyborg to Odense leg of our forthcoming cycle tour in Denmark – requires Google Earth installed on your desktop). Alternatively, use the Navigation Controls to zoom down and tilt the view, then drag and let go the hand symbol with your mouse in the opposite direction to the 'flight', keeping to the path by rotating the North point as required.
See also route planning in Google Earth »