GNSS and inertial technologies have a complicated mutual history.
Once competitors for navigation and positioning applications, they now appear ever more frequently in complementary roles — often within the same solution or system design.
Employing motion sensors (accelerometers), rotation sensors (gyroscopes), and a processing unit that integrates and processes the sensor data, an inertial navigation systems(INS) continuously calculates position, heading, and speed of a moving vehicle, vessel, or aircraft based on dead-reckoning principles.
Before GPS satellites were ever launched, triple redundant INS had become state-of-art technology in commercial and military aircraft. With a set of initial coordinates, pilots could guide their aircraft from one waypoint to the next using an INS to determine aircraft position and velocity.
More recently, automotive engineers have incorporated low-cost inertial technology into car and truck design to improve vehicle stability and control, and to aid on-board navigation systems.
One strength of an INS is its autonomy. Once an INS has been initialized it can operate without depending on external references or information. On the other hand, its dependence on relative positioning makes inertial navigation subject to internal error sources, which may be undetectable without outside aid.
Indeed, the ascendancy of GNSS technology over earlier technologies was foreshadowed in the 1983 KAL 007 incident and its aftermath when a commercial airliner flew off course over Soviet airspace and was shot down. Shortly after the incident, U.S. President Ronald Reagan announced that, following its completion, the Global Positioning System would be made available for civilian use, free of charge, in order to avoid similar navigational errors in the future.
Widespread adoption of GPS eventually revealed the practical limitations of this new technology, too — particularly in places that block or reflect satellite signals: underwater, underground, in steep terrain and urban “canyons,”and inside buildings.
Inertial technology is unaffected by such factors. Consequently, interest in bringing these two technologies together is growing among engineers on both sides of the GNSS/INS divide.
To help explain the state of play in GNSS/INS integration, we turned to Dr. Andrey Soloviev, a part-time research faculty at the University of Florida, Research and Engineering Education Facility, and president of Qunav, a small R&D business enterprise. Previously he served as a senior research engineer at the Ohio University Avionics Engineering Center.