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Abstract:Mapping agricultural crops is an important application of remote sensing. However, in many cases it is based either on hyperspectral imagery or on multitemporal coverage, both of which are difficult to scale up to large-scale deployment at high spatial resolution. In the present paper, we evaluate the possibility of crop classification based on single images from very high-resolution (VHR) satellite sensors. The main objective of this work is to expose performance difference between state-of-the-art parcel-based smoothing and purely data-driven conditional random field (CRF) smoothing, which is yet unknown. To fulfill this objective, we perform extensive tests with four different classification methods (Support Vector Machines, Random Forest, Gaussian Mixtures, and Maximum Likelihood) to compute the pixel-wise data term; and we also test two different definitions of the pairwise smoothness term. We have performed a detailed evaluation on different multispectral VHR images (Ikonos, QuickBird, Kompsat-2). The main finding of this study is that pairwise CRF smoothing comes close to the state-of-the-art parcel-based method that requires parcel boundaries (average difference ≈ 2.5%). Our results indicate that a single multispectral (R, G, B, NIR) image is enough to reach satisfactory classification accuracy for six crop classes (corn, pasture, rice, sugar beet, wheat, and tomato) in Mediterranean climate. Overall, it appears that crop mapping using only one-shot VHR imagery taken at the right time may be a viable alternative, especially since high-resolution OPEN ACCESSRemote Sens. 2015, 7 5612 multitemporal or hyperspectral coverage as well as parcel boundaries are in practice often not available.

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This letter introduces a new approach for the automated detection of circular oil tanks from single panchromatic satellite images. The new approach considers the symmetric nature of the circular oil depots, and it computes the radial symmetry in a unique way. We propose an automated thresholding method to focus on circular regions and a new measure, circle support ratio, to verify detected circles. Experiments are performed on GeoEye-1 test scenes, and the results reveal that the new approach is capable of detecting oil tanks with high success. The performance of our approach is also compared with leading techniques from the literature and has provided comparable or superior results.Index Terms-Circle detection, oil tanks, panchromatic satellite imagery, radial symmetry.

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