zt關於GPS兩大重要指標：地圖來源和路徑選擇

http://gpsmagazine.com/2007/06/garmin_vs_magellan_vs_tomtom_which_gps_picks_the_best_routes.php?page=2
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Map Provider：The two largest mapping data providers are NAVTEQ and Tele Atlas . NAVTEQ is more accurate and complete in North America, so it's preferable to buy a GPS that uses NAVTEQ rather than Tele Atlas (as of this writing).

All Magellan and Garmin GPS units use NAVTEQ mapping data, while TomTom uses Tele Atlas.

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Routing Test：All three tests showed Garmin's unit as the clear winner with the strongest routing engine. Magellan's Maestro unit performed admirably, coming in second place. TomTom's ONE XL (with TomTom's newest maps installed) came in a distant 3rd place in all three tests.