DOT-Z1 Pro Distance Measuring Instrument, Vehicle Installed Distance Measurer Measures distance and speed accurate to within 1 foot per mile. High-accuracy GPS-based measurements providing unparalleled accuracy and information. Extremely easy installation, just plug and go. It can even be hand-carried! Measures distance in feet, miles, and meters. Measures speed with 0.1 mph or kph precision. Large 8-digit LED display and USB interface.