Semantics-based satellite image retrieval using low-level features

Content-based techniques enable retrieval of remotely sensed data based on low-level features. However, the deep gap between low-level features and high-level semantics concepts is a major obstacle to more effective image retrieval. Therefore, a semantics-based retrieval approach was implemented. The semantics classifiers are trained using heterogeneous features from a group of satellite images. The proposed approach is mainly composed of two steps. The first step is to form hierarchical semantics classifiers based on the low-level features of the training images. In the second step, unknown satellite images are classified into a certain semantics class if their feature vectors are located in the corresponding feature space. To achieve an effective and at the same time efficient identification of the multiple semantics classes within the satellite scenes, an approximation approach was developed. At the query time, the system retrieves the satellite images based on semantics classes extracted from the query image or provided directly by the users