tailieunhanh - Field and Service Robotics- Recent Advances - Yuta S. et al (Eds) Part 4

Tham khảo tài liệu 'field and service robotics- recent advances - yuta s. et al (eds) part 4', kỹ thuật - công nghệ, cơ khí - chế tạo máy phục vụ nhu cầu học tập, nghiên cứu và làm việc hiệu quả | A Terrain-aided Tracking Algorithm for Marine Systems 99 The use of terrain information will be the key source of accuracy with this method. For areas in which the map information is sparse the observation of altitude will not provide much information with which to bound the uncertainty in position. The positioning accuracy achievable will also depend on the terrain over which the vehicle is travelling. A flat uniform bottom yields no information to bound the estimate of the filter. In this case the uncertainty in the estimate will grow along the arc subtended by the range observation. If on the other hand some unique terrain features are present such as hills and crevices the probability distribution will converge to a compact estimate. As shown in the example presented here the 2ơ uncertainty bounds converge to approximately 10m in the X and Y position estimates. The depth accuracy remains constant and is a function of the accuracy of the depth sensor. The uncertainty in the position estimate will grow while the body is not receiving altimeter readings. As shown in Figure 4 the error in the lateral position of the towed body relative to the ship grows large since there is no information available to the filter. Once the altimeter readings are received the uncertainty in both the X and Y positions are reduced. So long as the trend in the terrain elevation remains fairly unique the uncertainty will remain small. Sydney Harbour Demonstration In order to facilitate the demonstration of these techniques data sets taken in Sydney Harbour have been acquired. This data includes a detailed bathymetric map of the harbour shown in Figure 5 a and ship transect data including GPS and depth soundings shown in Figure 5 b . This data has kindly been donated by the Australian Defence Science and Technology Organization DSTO in relation to their hosting of the 3rd Shallow Water Survey Conference held in Sydney in November 2003. The particle filter based techniques described in