An Adversarial Approach to Discriminative Modality Distillation for Remote Sensing Image Classification

We deal with the problem of modality distillation for the purpose of remote sensing (RS) image classification by exploring the deep generative models. From the remote sensing perspective, this problem can also be considered in line with the missing bands problem frequently encountered due to sensor abnormality. It is expected that different modalities provide useful complementary information regarding a given task, thus leading to the training of a robust prediction model. Although training data may be collected from different sensor modalities, it is many a time possible that not all the information are readily available during the model inference phase. This paper tackles the problem by proposing a novel adversarial training driven hallucination architecture which is capable of learning discriminative feature representations corresponding to the missing modalities from the available ones during the test time. To this end, we follow a teacher-student model where the teacher is trained on the multimodal data (learning with privileged information) and the student model learns to subsequently distill the feature descriptors corresponding to the missing modality. Experimental results obtained on the benchmark hyperspectral (HSI) datasets and another dataset of multispectral (MS)-panchromatic (PAN) image pairs confirm the efficacy of the proposed approach. In particular, we find that the student model is consistently able to surpass the performance of the teacher model for HSI datasets.