From SEG Wiki
Revision as of 09:03, 25 March 2020 by Vinesh1609 (talk | contribs) (Added a page on one of the new remote sensing topics)
(diff) ← Older revision | Latest revision (diff) | Newer revision → (diff)
Jump to: navigation, search

Satellite Navigation is a method employing a Global Navigation Satellite System (GNSS) to accurately determine position and time anywhere on Earth. Satellite Navigation receivers are currently used by both private individuals and businesses for positioning, locating, navigating, surveying, and determining the exact time in an ever-growing list of personal, leisure and commercial applications. Using a GNSS system, the following values can accurately be determined anywhere on the globe

GNSS Positioning

Satellite Navigation Systems all use the same basic principles to determine coordinates:

o Satellites with a known position transmit a regular time signal.

o Based on the measured travel time of the radio waves (electromagnetic signals travel through space at the speed of light c = 300’000km/s) the position of the receiver is calculated.

o The distance D is calculated by multiplying the travel time delta t by the velocity of light C.

D = Delta t * C

Satellite Navigation Systems use satellites as time-signal transmitters. Contact to at least four satellites is necessary in order to determine the three desired coordinates (Longitude, Latitude, Altitude) as well as the exact time. Satellite Navigation Systems employ satellites orbiting high above the Earth and distributed in such a way that from any point on the ground there is line-of-sight contact to at least 4 satellites. Each one of these satellites is equipped with onboard atomic clocks. Atomic clocks are the most precise time measurement instruments known, losing a maximum of one second every 30,000 to 1,000,000 years. In order to make them even more accurate, they are regularly adjusted or synchronized from various control points on Earth. GNSS satellites transmit their exact position and onboard clock time to Earth. These signals are transmitted at the speed of light (300,000km/s) and therefore require approx. 67.3ms to reach a position on the Earth’s surface directly below the satellite. The signals require a further 3.33 s for each additional kilometre of travel. To establish position, all that is required is a receiver and an accurate clock. By comparing the arrival time of the satellite signal with the onboard clock time the moment the signal was transmitted, it is possible to determine the signal travel time.