If you sucessfully created a route and a trip plan in BASECAMP/MapSource, and after transferring the route to your GPS, your GPS routing is all wrong, or shows a straight line…then please read the following: 

Firstly, about transferring routes: we do not advise our clients to do this. The transfer of routes between Garmin’s BASECAMP and GPS is a dark science which yields different results based on which units are used.  It has nothing to do with the maps loaded.

However if you are going to try and do this then note the following:

• BASECAMP/MapSource and GPS must have the exact same maps loaded, i.e. the map you used for calculating the route in the first place must also be on the GPS
• The GPS will always recalculate the route once loaded (on some units you have to import the route after transferring it).  For this reason the route calculation settings on the GPS and your BASECAMP software must also be exactly the same else you will get different results.  E.g. if you use Shortest Distance on BASECAMP then GPS must also be set to Shortest Distance (these settings are not transferred to the GPS)
• In some cases it simply does not work.

If you succeed in transferring a route and you select this route then your GPS will now try to get you to the start of the route. If your starting point is different from what you calculated on the GPS you will have to recalculate the route from your current location.

We normally advise people to calculate their routes on BASECAMP in order to do their trip planning.  Then on the GPS on the day of your travel find the destination and let it calculate the route from where you are to that destination. You may want to print your itinerary or even send some crucial waypoints/POIs from your trip plan to your GPS which is then stored under Favourites for easy access, as waypoints/POIs to route to on your GPS.