Navigational apparatus for keeping track of the position of a vessel at sea which is particularly useful for small boats. A compass means 1 provides data in the form of an electrical signal, indicating the vessel's bearing. Speed measurement means 3, such as a trailed impellor, provides data in the form of an electrical signal, indicating the vessel's speed through the water. Tide data entry means allows data to be entered, in the form of an electrical signal, indicating the speed 8 and direction 9 (cos and sin outputs) of the tide. Computing means accepts the data and calculates the distance travelled from the starting point. indicating means 17 displays the position of the vessel and, preferably, the total distance travelled. The computing means may be analogue, digital or hybrid, and as shown includes multipliers 5, 6 acting on the sin and cos of the bearing signal, and the speed signal; and adders 10 and 11 for tide correction. IMAGE
展开▼
