dropCyclic: Snapshot Ensemble Convolutional Neural Network Based on a New Learning Rate Schedule for Land Use Classification

The ensemble learning method is a necessary process that provides robustness and is more accurate than the single model. The snapshot ensemble convolutional neural network (CNN) has been successful and widely used in many domains, such as image classification, fault diagnosis, and plant image classification. The advantage of the snapshot ensemble CNN is that it combines the cyclic learning rate schedule in the algorithm to snap the best model in each cycle. In this research, we proposed the dropCyclic learning rate schedule, which is a step decay to decrease the learning rate value in every learning epoch. The dropCyclic can reduce the learning rate and find the new local minimum in the subsequent cycle. We evaluated the snapshot ensemble CNN method based on three learning rate schedules: cyclic cosine annealing, max-min cyclic cosine learning rate scheduler, and dropCyclic then using three backbone CNN architectures: MobileNetV2, VGG16, and VGG19. The snapshot ensemble CNN methods were tested on three aerial image datasets: UCM, AID, and EcoCropsAID. The proposed dropCyclic learning rate schedule outperformed the other learning rate schedules on the UCM dataset and obtained high accuracy on the AID and EcoCropsAID datasets. We also compared the proposed dropCyclic learning rate schedule with other existing methods. The results show that the dropCyclic method achieved higher classification accuracy compared with other existing methods.