take use Doppler light and GPS to measuring speed and distance of running. Measurement system: dual beam Doppler measurement , 1MHzRange: forward: 0-40kt,0.1kt/level backward: 0-10kt,0.1kt/levelDisplay unit: 5.7-inch color LED 320 pixels *240 pixelsDistance range : 0-999,999.99nmSpeed accuracy: 0.2 knot(±2%) select the big oneOperation depth: deeper than 3 metersBackground color: Black Green ...