45 research outputs found
Improved Video Content Indexing by Multiple Latent Semantic Analysis
Low-level features are now becoming insufficient to build efficient content-based retrieval systems. Users are not interested any longer in retrieving visually similar content, but they expect retrieval systems to also find documents with similar semantic content. Bridging the gap between low-level features and semantic content is a challenging task necessary for future retrieval systems. Latent Semantic Analysis (LSA) was successfully introduced to efficiently index text documents by detecting synonyms and the polysemy of words. We have successfully proposed an adaptation of LSA to model video content for object retrieval and semantic content estimation. Following this idea we now present a new model composed of multiple LSA's (M-LSA) to better represent the video content. In the experimental section, we make a comparison of LSA and M-LSA on two problems, namely object retrieval and semantic content estimation
Analysis of layering-related linear features on comet 67P/Churyumov-Gerasimenko
We analysed layering-related linear features on the surface of comet
67P/Churyumov-Gerasimenko (67P) to determine the internal configuration of the
layerings within the nucleus. We used high-resolution images from the OSIRIS
Narrow Angle Camera onboard the Rosetta spacecraft, projected onto the SHAP7
shape model of the nucleus, to map 171 layering-related linear features which
we believe to represent terrace margins and strata heads. From these curved
lineaments, extending laterally to up to 1925 m, we extrapolated the subsurface
layering planes and their normals. We furthermore fitted the lineaments with
concentric ellipsoidal shells, which we compared to the established shell model
based on planar terrace features. Our analysis confirms that the layerings on
the comet's two lobes are independent from each other. Our data is not
compatible with 67P's lobes representing fragments of a much larger layered
body. The geometry we determined for the layerings on both lobes supports a
concentrically layered, `onion-shell' inner structure of the nucleus. For the
big lobe, our results are in close agreement with the established model of a
largely undisturbed, regular, concentric inner structure following a generally
ellipsoidal configuration. For the small lobe, the parameters of our
ellipsoidal shells differ significantly from the established model, suggesting
that the internal structure of the small lobe cannot be unambiguously modelled
by regular, concentric ellipsoids and could have suffered deformational or
evolutional influences. A more complex model is required to represent the
actual geometry of the layerings in the small lobe