GPS Speedometers: Quickly collect speedometers from GPS satellites, and the satellites can be locked in real time. More accurate than HUD OBD, GPS hud has the same working logic as speed radar. It has 100% versatility for all vehicles including cars, pickup trucks, off-road vehicles, trucks, trains, scooters, motorcycles, bicycles and boats. GPS HUD display:Driving Speed, Single Driving Time and Mileage. When using it in a car, plug it into the cars USB port. If there is no USB port in the car, you need a car adapter or plug it into a power bank (not included). Over-Speed Alarm: The default setting of vehicle speed is 120KM/H. When over-speed alarm is active, it will beep in 3 times to alert the car driver. Just need press the up or down to adjust it. If want to off speed warning, just adjust the over-speed value to a very impossible high value. Accuracy: As usual, its 2-5 KM/H off from the car engine speed. The display speed could be calibrated by hand easily. Make it 2-5 miles ahead to avoid speed ticket.