Garmin GPS devices read only GPX-formatted map set files, but not all maps are in this format. Both Google Maps and Google Earth applications read maps formatted in KML, while TomTom GPS devices read OV2 maps. To view maps obtained from sources like Google Maps in a Garmin, they must be converted from KML to GPX. There are several GPS conversion software programs and online tools that do this.
Go to GPS Visualizer's website and use its free online tool. Hit the "Choose" option and find the map in the browser window. Choose "GPX" as the output format, and convert the file.
Convert maps with the conversion tools with GPS Data Team's free tool. Pick a conversion option based on the original format of the map file (for example, OV2 or ASC) and select the correct conversion output. To convert OV2 to GPX, find the "Convert OV2 to GPX" link under OV2 Converters. Upload your map file from the save location to the conversion tool. Select the "Edit POIs Online" button, and the map is converted to Garmin format.
Install and then open the ExpertGPS software. Select the "Import Command" from the software's File menu. The software automatically converts the map to GPX format. This tool converts KML, SHP, DXF, CSV and many other file formats to GPX. As of 2010, ExpertGPS Home cost £48.70.