About: GPS+INS and where is it used?
What is an Inertial Navigation System (INS)? It is a device which measures rotation and acceleration and uses this information to calculate its position relative to the starting point. In contrast, GPS/GNSS provides absolute global positioning of any point which has GNSS satellite visibility. Combined, these two technologies create a powerful localization tool for accurate global positioning and orientation. GNSS/INS is frequently used in machine control and automation in industries such as construction, logistics and precision agriculture, especially in challenging environments where visibility of GNSS satellites is limited or obstructed.
Specialized GPS/GNSS receivers provide reliable precise positioning by using multi-frequency, multi-constellation GNSS technology. GPS receivers need a line-of-sight to at least 4 satellites to know where they are, and they need even more satellites for centimeter-level positioning (RTK). When the sky is temporarily blocked and the receiver loses GNSS satellite connection, other sensors such as IMU (Inertial Measurement Unit) take over by providing relative position to the last known location. This is referred to as coasting or dead reckoning. On top of improving availability of positioning, an IMU also provides 3D orientation (heading/yaw, pitch and roll angles) of an object. This is also referred to as attitude.