Global Navigation Satellite Systems

A satellite navigation or satnav system is a system that uses satellites to provide autonomous geopositioning. A satellite navigation system with global coverage is termed global navigation satellite system (GNSS). , four global systems are operational: the United States' Global Positioning System (GPS), Russia's Global Navigation Satellite System (GLONASS), China's BeiDou Navigation Satellite System, and the European Union's Galileo. Regional navigation satellite systems in use are Japan's Quasi-Zenith Satellite System (QZSS), a GPS satellite-based augmentation system to enhance the accuracy of GPS, with satellite navigation independent of GPS scheduled for 2023, and the Indian Regional Navigation Satellite System (IRNSS) or NavIC, which is planned to be expanded to a global version in the long term. Satellite navigation allows satellite navigation devices to determine their location (longitude, latitude, and altitude/elevation) to high precision (within a few centimetres to metres) using time signals transmitted along a line of sight by radio from satellites. The system can be used for providing position, navigation or for tracking the position of something fitted with a receiver (satellite tracking). The signals also allow the electronic receiver to calculate the current local time to a high precision, which allows time synchronisation. These uses are collectively known as Positioning, Navigation and Timing (PNT). Satnav systems operate independently of any telephonic or internet reception, though these technologies can enhance the usefulness of the positioning information generated. Global coverage for each system is generally achieved by a satellite constellation of 18–30 medium Earth orbit (MEO) satellites spread between several orbital planes. The actual systems vary, but all use orbital inclinations of >50° and orbital periods of roughly twelve hours (at an altitude of about ).

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Related exercises (21)

Satellite

A satellite turns turns around the earth on a circular orbit at a distance R of the centre of the earth.

What are the forces and accelerations ?
Compute the norm of the speed in terms of R.
Verify in this particular case Kepler’s 3^(rd) law.
Ariane launched a satellite on a circular orbit at a distance hu2004=u2004200u2006km for the earth. What are the speed and period of revolution of the satellite ?

Numerical application:

Gravitation constant: Gu2004=u20046.67u2005⋅u20051

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The numbered squares in the figure below represent the position of two blocs at 0.20 s intervals. The blocs are moving in the left to right direction. Compare their acceleration.
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Two material points, with identical mass m, are frictionlessly moving in a straight line, on a horizontal track (see diagram). They are attached together by a spring with constant K. Each material point is attached to a fixed point on the track by another spring, with constant k. The three springs have rest length l₀, and the fixed points are separated by a distance 3l₀.

Write each material point’s equations of motion.
Deduce the equations of motion of the center of mass and that system’s rela

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