Enhancing GPS/INS Navigation in Urban Environments through Collaborative Methods

1. Collaborative GPS/INS Navigation in Urban Environment Authors: F. Berefelt, B. Boberg, J. Nygårds, P. Strömbäck, S. L. Wirkander Swedish Defense Research Agency (FOI) Presented by: Mamadou Diallo ICS 280, Winter 2006

2. Goals • Problem • Degradation of GPS performance in urban environments due to blockages of LOS to satellites • A need to develop new navigation algorithms for urban environments • Solution: • GPS/INS method: based on collaboration and relative range or range vectors measurements • SLAM/INS method: based on laser range measurements and surrounding environment • GPS: ρi = |x - xi| + b + vi, i Є S • Inertial Navigation Systems (INS) • Self-contained navigation sensors • Growth of systematic errors • Integration GPS/INS • Precise positioning and attitude information • Model apply to a Kalman filter with the pseudo range equations

3. Methodology • Collaboration Methods • General • ρik = |Rik| = |xi-xk| + errors • ρi2 = |x2-xi|+b2+vi2, iЄS2 • X’1 = x1+ex1, d = x1–x2, d’ = d+ed • Virtual Satellite (VS) • |d’| = |d|+e|d| • Relative Vector (RV) • x’2=x’1–d’ = x2+ex1-ed • Shared Pseudoranges (SP) • x1=x2+d’ -ed • Simultaneous Localization and Map Building (SLAM) • Vehicle position estimated based on prior knowledge - map • Concurrently estimate static objects in the environment and state of the navigation vehicle • Position, orientation

4. Results • Simulation model • 16 houses, 4 blocks, • V: 1m/s, GPS/INS, laser device Simulation Results • VS: blue, RV: green , SP: red • Period: 0-45s, no LOS, errors increase • Period: 45s-55s, LOS • VS & RV: S-N improved, but not E-W • SP: V2 uses 2S observed by v1, E-W positional error reduced • Period: 56s-75s, no LOS, errors increase • Period: 76s-130s, LOS • V2 Positional errors decrease, positional uncertainty decrease

5. Questions?