Tham khảo tài liệu 'vision systems - applications part 5', kỹ thuật - công nghệ, cơ khí - chế tạo máy phục vụ nhu cầu học tập, nghiên cứu và làm việc hiệu quả | Bearing-Only Vision SLAM with Distinguishable Image Features 151 landmark in the database are provided by the frame memory. For every new observation of a landmark the descriptor is compared to the existing ones and used to augment the descriptor list if it is different enough. The SIFT point descriptors are not globally unique see Figure 2. again and thus matching a single observation to a landmark is doomed to cause false matches in a realistic indoor environment. However using large number of SIFT descriptors has proven to give robust matching results in object recognition applications. This is why we store along with the landmark descriptor associated with the location of the landmark the rest of the descriptors extracted from the same frame and use these for verification. We refer to the rest of the feature points in a frame as recognition features to distinguish them from the location feature associated with the location of the landmark. The structure of the database is shown on the right hand side in Figure 3. Each landmark F1 F2 . FN has a set of location descriptors shown in the dashed box. A KD-tree representation and a Best-Bin-First Beis Lowe 1997 search allow for real-time matching between new image feature descriptors and those in the database. Each location descriptor has a set of recognition descriptors shown to the right. When we match to the database we first look for a match between a single descriptor in the new frame and the location descriptors of the landmarks dashed box Figure 3. . As a second step we match all descriptors in the new frame to the recognition descriptors associated with candidate location descriptors for verification. As a final test we require that the displacement in image coordinates for the two location features new frame and database is consistent with the transformation between the two frames estimated from the matched recognition descriptors new frame and database . This assures that it is not just two similar .
