Ok, I have learned quite a bit about navigation using GPS in the last few months. I am not a expert but I will try to relay some useful info.
First, Garmin Edge units are expensive. Garmin Etrex units are not. Unless you need the powertap or HRM functions of the Edge units, save yourself about 300 dollars and look at a etrex 20 unit. The eTrex 20 or 30 units also use AA batteries. This is a huge advantage if you are going out for multiple days and do not have the capacity to recharge your Edge. They are not as slim and trim as a Edge 800 or 705, but serve the same function.
Namely they allow you to load a base map and to navigate preconceived routes.
- Base Map- this is the primary functionality for most riders that like to explore on their bike. Garmin offers North america street maps for about $70 or you can get free maps through the Open Street Map Project (OSM). Here are the instructions for using OSM on your Garmin. You can download recently updated OSM Map for North America here. You may have to save the maps to a microSD card depending on how much memory your Garmin has.
- You can use OSM on your iPhone GPS when there is no cell signal, however I would be too concerned about the battery life to solely rely on a iPhone to navigate the gravel conspiracy course. There will be no cell service once we get away from the north shore.
- Creating routes: I have found the most useful free program for creating routes to be Bike Route Toaster All of the routes for the Gravel Conspiracy were created with BRT. I also love that it allows you to create cue sheets. Remember that routes created for Garmin Edge units should be saved as .tcx files, all other gps units will use .gpx files. Once you have a .gpx or .tcx file that you want to load on your GPS, you plug your GPS into the computer. Under "My Computer" Click on the name of your device and open a folder called "new files". Drag and drop your .tcx or .gpx files into the "new files" folder. Thats it. The next time you power up the device your route should appear on the GPS. Then you just follow the line.