Provides accurate speed over ground readings and heading information all in one attractive package. This product is ideal for all speed applications and is particularly useful for slow and high speeds where traditional speed sensors like pitot tubes and paddlewheels do not perform well. An added advantage is there is nothing in the water to corrode or break. Features: Included LCD heading display to show course over ground Connects to an existing NMEA 0183 GPS device (not included) Speed accuracy of +/-1 MPH (once moving) Heading accuracy of +/-1 degree (once moving) Enhanched illumination: through-dial lighting for excellent readability at night