Navigation in GPS Denied

This paper focuses on the latest technology trends for navigating in difficult urban, indoor, and underground environments where typical Global Positioning System (GPS) receivers do not function. The latest alternative navigation (Alt-Nav) technologies based on electro-optical techniques are described. These techniques extract features from electro-optical images (for example, a point feature associated with a corner of a building or a line associated with a wall of an indoor hallway) and then utilize those features as navigation related landmarks to enable aiding of inertial navigation system (INS). The Alt-Nav technologies presented include optically-aided INS and Ladar-aided INS. Tightly integrating these technologies with an INS should lead to navigation performance similar to that is achieved in today’s GPS/INS integrations. An Alt-Nav integration vision for the future is given with some example configurations that improve overall navigation system robustness. 1.0 MOTIVATION AND BACKGROUND Over the past couple of decades, there have been a number of navigation trends that have driven the desire to improve our ability to navigate in all environments. Table 1 notionally represents these trends. Previously, the primary desire was to navigate single, stand-alone systems (such as a car), but now, the desire is increasingly Navigation in GPS Denied Environments: Feature-Aided Inertial Systems 7 2 RTO-EN-SET-116(2011) to have simultaneous navigation awareness of multiple interdependent systems (such as a traffic notification system in a car). Previously, navigation capability was not always counted on, but increasingly navigation is considered to be an assumed infrastructure (like knowing the lights will come on when you turn on the light switch). Previously, navigation accuracy of 5-10 m seemed almost extravagant when other worldwide navigation options prior to GPS (namely, Omega [1] and stand-alone inertial) had accuracies more on the order of 1-2 km. Now, there are many applications that require meter or sub-meter level accuracy (such as precision agriculture). Previously, due to cost, power, and size constraints, it was generally only feasible to know where the “big things” are (such as airplanes). Now, navigation is desired on more and more, smaller and smaller objects (such as cell phones). Table 1: Navigation Trends.