NOTE: Free essay sample provided on this page should be used for references or sample purposes only. The sample essay is available to anyone, so any direct quoting without mentioning the source will be considered plagiarism by schools, colleges and universities that use plagiarism detection software. To get a completely brand-new, plagiarism-free essay, please use our essay writing service.
One click instant price quote
Navigation is the science of conducting a vessel to a certain destination. The two types of navigation that I will discuss are global positioning using satellites and celestial navigation. For centuries sailors have guided their ships across the oceans by celestial navigation or nautical astronomy. This is the art of finding position by observing the sun, moon, stars and planets. As they journey for some distance, travelers observe that the celestial bodies appear to change their paths across the sky and to rise and set at new points along the horizon. Since the apparent positions of celestial bodies thus change with time and with changes in an observers position on the nearly spherical earth, the location of a ship or other craft may be determined by careful observations of celestial bodies.
Celestial bodies such as the stars are so far from the earth that they appear to be located on the inside surface of an imaginary hollow sphere. This sphere which has an infinite radius is called the celestial sphere. Its center coincides with the center of the earth. All points on the earths surface are considered to be projected onto the celestial sphere, as are the equator, the parallels of latitude, and the meridians. For the purpose of navigation, a system of coordinates is required on the celestial sphere in order that the position of a celestial body at any time may be accurately described.
One such system is the celestial equator or equinoctial system. In this system the celestial equator or equinoctial is the base or primary circle. It corresponds to the earths equator. At right angles to the celestial equator are the hour circles. An hour circle is a great circle on the celestial sphere that passes through the poles and through a celestial body or point.
Each meridian of the celestial sphere is identical with an hour circle. The declination (dec. ) of any point on the celestial sphere is its angular distance north or south from the celestial equator, measured along the hour circle that passes through the point. Declination on the celestial sphere corresponds to latitude on the earths surface. The Greenwich hour angle (GHA) of any point or body is the angle measured at the pole of the celestial sphere between the celestial meridian of Greenwich and the hour circle of the point. The angle is measured along the celestial equator westward from the Greenwich celestial meridian from 0? through 360? .
The GHA differs from longitude on the earths surface in that longitude is measured east or west from 0? through 180? and remains constant. The GHA of a body increases through each day as the earth rotates. The GPS satellites orbit the earth twice a day, 11, 000 miles above the earth, transmitting their precise signal position and elevation.
The GPS receiver acquires the signal, then measures the interval between transmission and receipt of the to determine the distance between the receiver and the satellite. Once the receiver has calculated this data for at least 3 satellites, its location on the earths surface can be determined.
Free research essays on topics related to: celestial bodies, celestial, equator, sphere, earths surface
Research essay sample on Celestial Bodies Earths Surface
