Ensimmäiselle sivulle GPS-route testing

Ensimmäiselle sivulle Introduction n Goal is to introduce the results of GPS-route accuracy tests n Discuss about the problems encountered while testing GPS- receivers

Ensimmäiselle sivulle Contents n What effects GPS-signal accuracy n Tested GPS-receivers n Test setting n Encountered problems n Test results

Ensimmäiselle sivulle Uncontrollable variables n Satellite coverage n Weather n Obstacles in route (roadworks, traffic lights, etc.) n Although uncontrollable, these can be taken into account when planning testing

Ensimmäiselle sivulle Controllable variables n Devices n Route n Device position n Location refresh rate (8s. intervals) n Travelling method & speed

Ensimmäiselle sivulle Test setting n 8 tested devices u 5 mobile phones using internal receiver u 2 external Bluetooth receivers u 1 wrist GPS n Clear weather

Ensimmäiselle sivulle Test route

Ensimmäiselle sivulle Possible problems n Synchronizing n Separating sequentially recorded routes from each others n Acquiring accurate reference route & map anomalies n Battery charge n Data transfer (contracts & costs)

Ensimmäiselle sivulle Measuring error to reference n Different ways to calculate distance between routes n The DP-algorithm used: u for each actual point count distance to each of the remaining reference points F pick smallest F sum to optimal distance so far u Divide optimal sum with number of actual points within route

Ensimmäiselle sivulle Problems with algorithm n Given results are better than what’s the actual error n This is due to comparing actual points to closest points in the reference route

Ensimmäiselle sivulle Assumptions and results n N95 slider-state might effect accuracy n External receivers are expected to produce better results n Wrist GPS is expected to provide better accuracy than integrated mobile phone receivers n Every device produced accuracy of less than 10 meters

Ensimmäiselle sivulle Ranking of tested devices n m n N95-2, open 3.13m n N95-1 w/ external (Pretec) 3.61m n Garmin wrist-GPS (1s.) 3.69m n Garmin wrist-GPS (8s.) 3.75m n E m n E m n N95-2, closed 6.05m n N95-2 w/ external (Fortuna) 6.44m

Ensimmäiselle sivulle Example of actual routes (external) Pretec Fortuna

Ensimmäiselle sivulle Another example Fortuna Pretec

Ensimmäiselle sivulle Further improvements n Implementing different kind of measurement algorithm n Creating better reference route