There are five basic forms of navigation:
- Pilotage, which essentially relies on recognizing landmarks to know where you are and how you are oriented. It is older than humankind.
- Dead reckoning, which relies on knowing where you started from, plus some form of heading information and some estimate of speed.
- Celestial navigation, using time and the angles between local vertical and known celestial objects (e.g., sun, moon, planets, stars) to estimate orientation, latitude, and longitude .
- Radio navigation, which relies on radiofrequency sources with known locations (including global navigation satellite systems satellites).
- Inertial navigation, which relies on knowing your initial position, velocity, and attitude and thereafter measuring your attitude rates and accelerations. It is the only form of navigation that does not rely on external references.
These forms of navigation can be used in combination as well [18, 26, 214]. The subject of this book is a combination of the fourth and fifth forms of navigation using Kalman filtering.
1.1 GNSS/INS INTEGRATION OVERVIEW
Kalman filtering exploits a powerful synergism between the global navigation satellite systems (GNSSs) and an inertial navigation system (INS). This synergism is possible, in part, because the INS and GNSS have very complementary error characteristics. Short-term position errors from the INS are relatively small, but they degrade without bound over time. GNSS position errors, on the other hand, ...