All new global positioning systems (GPS) come with installed maps. Typically these maps are minimal and don't include many points of interest or up-to-date routing information. Manufacturers offer updates for these maps on their individual company websites. There is other software available for varying formats, some specific and some open for all systems to use. The main issues in updating GPS maps are determining which system your unit uses, and choosing which update is right for you.
Determine which type of global positioning system you use. This can vary by manufacturer and the operating system installed on the GPS unit. Downloading maps for the wrong system will do nothing for your GPS maps. Also, make sure that your GPS has the capability to be connected to your computer, otherwise you will only be able to get your maps from a map disc or through the unit itself, and not for free.
Search for the software needed for your particular GPS. If you aren't sure which operating system is installed on your GPS, do an internet search for the manufacturer's website. For instance, if you have a Tom Tom GPS, searching for "Tom Tom maps" or "free Tom Tom maps" will result in many sites where updates can be found for free.
Connect your GPS unit to your computer.
Download the maps onto your computer. Then move them onto your GPS unit by saving the map to your computer, hooking your GPS unit through a USB port and clicking and dragging the map into the "Maps" or similar folder on the unit. You may also directly download the maps to your GPS unit by selecting the unit's "Maps" (or similar) folder as the destination when saving downloaded maps.