The IRNSS (NavIC) enables providing position, navigation, and timing information for civil and strategic applications like
Terrestrial, aerial and marine navigation
Precise timing
Disaster management and alert messages
Mapping and Geodetic data capture
Vehicle tracking and fleet management
Visual & voice navigation for drivers
Details of NavIC
Seven satellites of NavIC constellation are in orbit- another satellite is planned for launch during first quarter of 2018.
NavIC provides signals in a space covering India and its surroundings
Signal in space is provided globally by GPS of USA, GLONASS of Russia, Galileo of Europe, and Beiden of China.
Current trend is use ground receivers, which utilize as many signals as available for providing timing and position solutions.
What is GPS?
The Global Positioning System (GPS) is satellite-based navigation system made up of at least 24 satellites.
Ideally, GPS should work in any weather conditions, anywhere in the world, 24 hours a day.
The U. S. Department of Defense (USDOD) put the satellites for military use, but they were made available for civilian use in the 1980s.
GPS satellites circle the Earth twice a day in a precise orbit.
Each satellite transmits a unique signal and orbital parameters allowing GPS devices to decode and compute the precise location of the satellite. GPS receivers use this information to trilateration exact location.
For trilateration, GPS receiver measure the distance to each satellite by the amount of time it takes to receive a transmitted signal.
GPS receiver requires signal of at least 3 satellites for 3-D position and 4 or more satellites for 3-D position (latitude, longitude, and altitude) .
GPS receivers are typically accurate to within 10 meters. Accuracy is even better on the water.