Digital navigation calculators for assessing the ship’s position by simple operation with built-in programs. Easy-to-understand dialogue system telling what input data is required, and what output data is displayed. Major navigation functions are; - Simple operation with built-in programs, - Course and Distance computation. - Dead Reckoning computation, - Great Circle computation, - ETA computation, - Current computation. - LOP computation. - Meridian Passage computation. - Convenient conversions for to HMS and to HHHH. - Long term Nautical Almanac for the Sun, Moon, Venus, Mars, Jupiter, Saturn and 63 stars. The built-in Almanac is usable until 2100, and it is good with accuracy better than 0’.2.. - Twilight time mode computes times of rise or set, civil twilight and azimuth for the Sun and rise or set, age and azimuth for the Moon, - Prediction/identification mode computes azimuth and altitude for all celestial bodies and displays any usable bodies above the horizon, - Can input Latitude and Longitude from optional GPS receiver.