Ground penetrating radar (GPR) target detection and classification is a challenging task. Here, we consider various online dictionary learning (DL) methods to obtain sparse representation (SR) of the GPR data to enhance feature extraction for target classification via support vector machine. Online methods are preferred because traditional batch DL like K-SVD is not scalable to high-dimensional training sets and infeasible for real-time operation. We also develop Drop-Off MINibatch Online Dictionary Learning (DOMINODL) which exploits the fact that a lot of the training data may be correlated. The DOMINODL algorithm iteratively considers elements of the training set in small batches and drops off samples which become less relevant. For the case of abandoned anti-personnel landmines classification, we compare the performance of K-SVD with three online algorithms: classical Online Dictionary Learning, its correlation-based variant and DOMINODL. Our experiments with real data from L-band GPR show that online DL methods reduce learning time by 36-93% and increase mine detection by 4-28% over K-SVD. Our DOMINODL is the fastest and retains similar classification performance as the other two online DL approaches. We use a Kolmogorov-Smirnoff test distance and the Dvoretzky-Kiefer-Wolfowitz inequality for the selection of DL input parameters leading to enhanced classification results. To further compare with state-of-the art classification approaches, we evaluate a convolutional neural network (CNN) classifier which performs worse than the proposed approach. Moreover, when the acquired samples are randomly reduced by 25%, 50% and 75%, sparse decomposition based classification with DL remains robust while the CNN accuracy is drastically compromised.2 Furthermore, online DL 2 methods have been studied more generally in GPR. Only one other previous study has employed DL (K-SVD) using GPR signals [24], although for the application of identifying bedrock features. We employ online DL methods and use the coefficients of the resulting sparse vectors as input to a SVM classifier to distinguish mines from clutter. Our comparison of K-SVD and online DL using real data from L-band GPR shows that online DL algorithms present distinct advantages in speed and low false-alarm rates.2) A new, faster online DL algorithm. We propose a new Drop-Off MINi-batch Online Dictionary Learning (DOMINODL) which processes the training data in mini-batches and avoids unnecessary update of the irrelevant atoms in order to reduce the computational complexity. The intuition for the dropoff step comes from the fact that some training samples are uncorrelated and, therefore, in the interest of processing time, they can be dropped during training without significantly affecting performance.3) Better statistical metrics for improved classification. Contrary to previous studies [24] which determine DL parameters (number of iterations, atoms, etc.) based on bulk statistics such as normalized root-mean-square-error (NRMSE), we consider statistical inference for...