To plan routes on your PC/ Mac for your SatMap you can use SatSync.

SatSYNC is a free piece of software that allows you to connect your Satmap GPS to your PC. 

With this software you can upload and download Routes, Trails and Points Of Interest. 

These files can be viewed, formatted and shared on Satmap Xpedition. 

You can view your trail on detailed topographical mapping, aerial or street maps with Satmap Xpedition.

More info about SatSync can be found here.