GPS Speedometer: Quickly acquires speed readings from GPS satellites for real-time accuracy. More precise than OBD HUDs, it operates on the same principle as radar speed guns. Universally compatible with all vehicles, including cars, trucks, ATVs, motorcycles, bicycles, and boats. GPS HUD Display: Shows driving speed, single trip time, and distance. Connect to your car's USB port for power. If your car lacks a USB port, use a car adapter or a power bank (not included). Overspeed Alarm: Default overspeed alarm is set at 120 km/h. It will beep 3 times to alert the driver. You can easily adjust this setting using the up/down buttons. To disable the alarm, set the overspeed value to an impossibly high number. Accuracy: Typically within 2-5 km/h of your car's speedometer. The display speed can be manually calibrated to ensure accuracy and avoid speeding tickets.