Satellite Navigation

Question 1

Describe principles of the satellite navigation.

Answer 1

a system of satellites that provide autonomous geo-spatial positioning with global or local coverage.

Each satellite continually transmits messages that include
1. time the message was transmitted
2. precise orbital information
3. the general system health and rough orbits of all navigation satellites

The receiver uses the messages to determine the transit time of each message and computes the distance to each satellite. These distances along with the satellites’ locations are used with the possible aid of trilateration to compute the position of the receiver.

Question 2

Describe all global satellite navigation systems functioning at present

Answer 2

1. GPS (Global Positioning System): Developed by the United States Department of Defence, the Global Positioning System (GPS) is a global navigation satellite system that provides geolocation and time information to a GPS receiver anywhere on or near the Earth where there is an unobstructed line of sight to four or more GPS satellites.
2. GLONASS (Global Navigation Satellite System): Developed by the Russian Aerospace Defence Forces, GLONASS is a space-based navigation system that provides real-time positioning and speed information for military and civilian users in Russia and around the world.
3. Galileo: Developed by the European Union, Galileo is a global navigation satellite system that provides a high-precision positioning service to users in Europe and around the world.
4. BeiDou: Developed by the People’s Republic of China, BeiDou is a regional navigation satellite system that provides positioning and timing services to users in the Asia Pacific region.
5. QZSS: Developed by the Japanese government, QZSS is a regional navigation satellite system that provides high-precision positioning and timing services to users in the Asia Pacific region.
6. IRNSS: Developed by the Indian Space Research Organisation, IRNSS is a regional navigation satellite system that provides real-time positioning and timing services to users in India and the surrounding region.

Question 3

Give a list of the sources of errors in position determination by the satellite
navigation.

Answer 3

1. Atmospheric delay of the satellite’s signal (troposphere, ionosphere)
2. Signal multipath (reflection)
3. Receiver clock error
4. Orbital (ephemeris) error
5. Low number of visible satellites
6. Satellite mutual position
7. Intentional degradation of signals