Object Classification of Aerial Images With Bag-of-Visual Words

This letter presents a Bag-of-Visual Words (BOV) representation for object-based classification in land-use/cover mapping of high spatial resolution aerial photograph. The method is introduced to handle the special characteristics of aerial images, i.e., variability of spectral and spatial content. Specifically, patch detection and description are used to divide and represent various subregions of objects comprising multiple homogeneous components. Moreover, the BOV representation is constructed with the statistics of the occurrence of visual words, which are learned from the training data set. A combination of spectral and texture features is verified to be a satisfactory choice through the evaluations of various patch descriptors. Furthermore, a threshold-based method is employed to reduce the impact of outliers on classification in test data. Experiments based on aerial-image data set show that the proposed BOV representation yields better classification performance than the low-level features, such as the spectral and texture features.