Category: General Navigation

Grid Navigation Introduction to Grid Navigation Grid navigation helps in avoiding the steering problems at high latitudes True or magnetic directions are unusable in in high latitudes due to 3 reasons Rapid convergence causes true track to change rapidly Magnetic variation is high and varies considerably Magnetic compass is ineffective due to lesser horizontal component Grid Charts Grid charts are created by nominating a datum meridian and calculating directions throughout the chart with the datum meridian Grid charts have a square grid instead of latitude longitude graticules Grid charts are…

Sunrise & Sunset Sunrise and Sunset The tilt of spin axis of the earth with the orbital plane results in seasonal variation in duration of daylight The time of sunrise and sunset are affected by certain factors A combination of Sun’s Declination and observer’s latitude affects the duration of daylight Semi-diameter or radius of the sun also affects sunrise and sunset Refraction of light in the atmosphere increases daylight time Effect of Sun’s Declination on Sunrise and Sunset Declination of the sun affects the time of sunrise and sunset Consider…

Measurement of Time Hour Angle Hour angle is the arc of the equinoctial which is equivalent of longitude Hour angle is measured westwards from 0° to 360° between datum meridian and meridian of celestial body Hour angle varies constantly due to rotation of earth Hour angle is 000 degrees, when the celestial body transits a given meridian When the body transits the anti-meridian, its hour angle is 180 degrees Greenwich and Local Hour Angles Hour angles are called either Greenwich or Local hour angles based on the selected datum meridian…

Calculation of Year, Day and Time Sidereal Year Sidereal year the duration taken for one revolution of the earth around the sun with distant star at infinity as datum reference Time taken for one sidereal year is equal to 365 days and 6 hours Tropical Year Tropical year is duration taken for one revolution of the earth around the sun with sun as the datum reference Duration of tropical year is 365 days, 5 hours, 48 minutes and 45 seconds Calendar Year Calendar year is made to keep whole number…

Solar System Kepler’s First Law of Planetary Motion Kepler propounded three laws regarding planetary motion Kepler’s first law states that the orbit of each planet is an ellipse with the Sun at one of the foci Kepler’s second law states that the line joining the planet to the Sun sweeps equal areas in equal time Kepler’s third law states that the square of the sidereal period of a planet is proportional to the cube of its mean distance from the Sun Orbit of Planets around the Sun All planets revolve…

Lamberts vs Mercator Plotting Plotting Radio Bearings on Lambert Charts Radio bearings can be plotted on Lambert Charts by following these steps Step 1 – Convert Relative bearings to Magnetic Bearings Formula for Magnetic bearings = Relative bearing + Magnetic heading If the value of magnetic bearing is greater than 360 Subtract 360 from the result Step 2 – Convert Magnetic bearings to the station (QDM) to Magnetic Bearings from the station (QDR) Step 3 – Convert Magnetic Bearing (QDR) to True Bearings (QTE) Get True Bearings by Applying Station…