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 Collaborative GPS/INS Navigation in Urban Environment

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: ρ i = |x - x i | + 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

Methodology Collaboration Methods  General ρ i k = |R i k | = |x i -x k | + errors ρ i 2 = |x 2 -x i |+b 2 +v i 2, iЄS 2 X’ 1 = x 1 +e x1, d = x 1 –x 2, d’ = d+e d  Virtual Satellite (VS) |d’| = |d|+e |d|  Relative Vector (RV) x’ 2 =x’ 1 –d’ = x 2 +e x1 - e d  Shared Pseudoranges (SP) x 1 =x 2 +d’ - e d 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

Results 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 Simulation model 16 houses, 4 blocks, V: 1m/s, GPS/INS, laser device

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