MagVar 2020 对比 Perpetual Nautical Almanac 的使用情况和统计数据

MagVar 2020

MagVar 2020 is targeted towards anyone interested in navigation. This includes, pilots of aircraft, captains of sea going vessels, cartographers, engineers and surveyors. Anyone who uses maps and a compass will find the declination calculation (also referred to magnetic variation) very useful. (Declination is the difference between true and magnetic north and used when plotting a course on a map.) MagVar 2020 calculates the magnetic flux density for any location on the Earth and then uses this data to calculate magnetic variation. The model is accurate for dates ranging from January 1, 2020 up through December 31, 2024. Using the model, the app calculates declination and inclination. As the user pans the map, the magnetic variation is calculated and graphically shown as a map overlay.

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Perpetual Nautical Almanac

Using the U.S. Naval Observatory NOVAS library and solar system ephemerides from JPL, high precision positions can be calculated in real-time from 1900 to 2050. Simply select date and time and all values are recalculated instantly. The estimated elevation value is only needed for calculating sunrise/sunset, twilight, and moonrise/moonset. The app provides the following functionalities: *Aries: GHA position *Sun: -GHA/dec - Astronomical dawn, nautical dawn, civil dawn, sunrise, sunset, civil dusk, nautical dusk, astronomical dusk, and meridian passage at Greenwich. - Semidiameter - Sunlight world map with the Sun and the Moon position. *Moon: - GHA/dec - Moonrise/moonset and meridian passage at Greenwich. - Semidiameter - Moon phase and age of the Moon. *Planets: - GHA/dec for Venus, Mars, Jupiter, and Saturn. *Stars: - Magnitude, SHA/dec of 99 stars ordered by SHA. *Corrections: - Correction for the atmospheric refraction. - Correction for the dip of the horizon. - Parallax correction for the Moon, the Sun, Venus, and Mars.