NavIC Regional Satellite Navigation System

NavIC is India's satellite navigation system, which helps users determine their location and time. Developed by the Indian Space Research Organisation (ISRO), Navigation with Indian Constellation (NavIC) uses satellites, ground stations and user receivers to provide positioning, navigation and timing services over India and its surrounding region.

A constellation designed for regional coverage

Unlike a global navigation constellation, NavIC concentrates its coverage on a specific region. Its primary service area includes India and approximately 1,500 km beyond its boundary.

• The original constellation was designed with seven satellites: three in geostationary orbits and four in inclined geosynchronous orbits.
• Geostationary satellites appear fixed above the equator, while inclined geosynchronous satellites move in a repeating pattern in the sky.
• Both orbital types have a period matching Earth's rotation; their arrangement provides sustained satellite visibility over the intended service region.

How a receiver calculates its position

NavIC works through one-way ranging: satellites broadcast navigation signals, and a receiver uses their travel times to estimate its distance from each satellite. The receiver does not need to transmit its location to the satellites.

• Satellite signals carry precise transmission-time information and orbital data, allowing the receiver to determine where each satellite was when its signal was sent.
• The receiver multiplies signal travel time by the speed of light to estimate distance; this measurement is called a pseudorange because it includes clock and other errors.
• Signals from at least four satellites normally allow a receiver to solve simultaneously for three-dimensional position and its own clock error.
• A ground control segment monitors satellite orbits and clocks and uploads navigation information and corrections for broadcast to users.
• Satellite geometry, atmospheric delays, reflected signals and receiver quality affect the accuracy of the resulting position.

Signals, services and practical value

NavIC provides a Standard Positioning Service (SPS) for civilian users and a Restricted Service (RS) that is encrypted and available to authorised users.

• The original system broadcasts navigation signals in the L5 and S bands; dual-frequency measurements help estimate and correct ionospheric delay.
• Its stated design objective is position accuracy better than 20 metres in the primary service area; actual performance depends on reception conditions.
• Applications include road and marine navigation, surveying, mapping and precise timing.
• An independently controlled regional system reduces dependence on foreign navigation services for strategic and civilian requirements.