Most GPS units use SD cards to save map files. The SD card can easily be removed from the GPS unit, and you can transfer the map files from the SD card onto your computer. Once the map files are on the computer, you can transfer them to another storage device, including another SD card. This can be useful if you need to transfer data from one GPS unit to another.
Remove the SD card from the GPS unit.
Insert the SD card into the SD card reader slot on your computer.
Click on the "Start" logo in the lower left-hand corner of your computer's desktop screen. Select "Computer". Choose the SD card from the drive menu and double-click it. All the files on the SD card will be displayed. Drag and drop the map files into the "C:/" drive. Safely remove the SD card from the slot.
Insert the new SD card into the SD card reader; this is the card you want to put the maps onto.
Choose the "C:/" drive in the drive menu in "Computer". Drag and drop the map files from the hard drive into the SD card. Remove the SD card.
Make backup copies of map files to store on your computer's hard drive;this way, if they accidentally get deleted from the SD card, you will have copies to put back onto it.
Different GPS units are not compatible with all SD cards.