The use of object detection algorithms for the analysis of satellite imagery is increasing in various fields, including environment and defense, as they enable the automatic detection, recognition and localization of targets. Satellite images often exhibit significant variations, including differences in resolution and noise levels between different satellites. Additional distortions can be caused by factors such as the position of the satellite and the specific area being scanned, resulting in changes in tangential distortion, brightness and saturation. Depending on the severity, these variations can affect the visual clarity of objects in the images and thus impair the effectiveness of object detection algorithms. This study therefore investigates the effects of such fluctuations on the performance of 3 categories of object recognition algorithms - YOLO, FASTER-RCNN and RT-DETR - by applying the principle of adversarial attacks to the inference phase of the algorithms. This experiment makes it possible to uncover the weaknesses of the algorithms facing different degrees of 5 types of satellite images noises. The case study presented is based on the automatic detection of three types of oil and gas infrastructure: compressor, tank and well in the Permian Basin (USA).

Reducing methane emissions is essential to tackle climate change. Here, we address the problem of detecting automatically point source methane leaks using high resolution hyperspectral images from the PRISMA satellite. We use a variation of the Matched Filter (MF) called the Adjusted Spectral Matched Filter (ASMF) to detect methane plumes in satellite images. To remove false positives, the detected plumes are confirmed by comparing their orientation to the wind direction extracted from the standard meteorological reanalysis product ERA5. The ASMF reduces the fraction of false detections compared to the MF and without preventing the detection of plumes. To validate the method, we use a recently proposed dataset of manually annotated plumes on PRISMA images. We also compare our detection rate to the detection rate of methods using deep learning or the standard matched filter. We then show that our method outperforms those methods in terms of F1 score.

Reducing methane emissions is essential to tackle climate change. Here, we address the problem of detecting large methane leaks by using hyperspectral data from the satellite Sentinel-5P. By sampling Sentinel-5P spectral data at fine scale, we detect methane absorption features in the shortwave infrared wavelength range (SWIR). Our method involves two separate steps: i) background subtraction and ii) detection of local maxima in the negative logarithmic spectrum of each pixel. In the first step, we remove the impact of the albedo using albedo maps and the impact of the atmosphere by using a principal component analysis (PCA) over a time series of past observations. In the second step, we count for each pixel the number of local maxima that correspond to a subset of local maxima in the methane absorption spectrum. This counting method allows us to set up a statistical a contrario test that controls the false alarm rate of our detections.

Hydraulic fracturing (or "fracking") is a revolutionary well stimulation technique for shale gas extraction, but has spawned controversy in environmental contamination. If methane from gas wells leaks extensively, this greenhouse gas can impact drinking water wells and enhance global warming. Our work is motivated by this heated debate on environmental issue and focuses on general data analytical techniques to detect anomalous spatial data samples (e.g., water samples related to potential leakages). Specifically, we propose a spatial outlier detection method based on contextual neighbors. Different from existing work, our approach utilizes both spatial attributes and non-spatial contextual attributes to define neighbors. We further use robust metric learning to combine different contextual attributes in order to find meaningful neighbors. Our technique can be applied to any spatial dataset. Extensive experimental results on five real-world datasets demonstrate the effectiveness of our approach. We also show some interesting case studies, including one case linking to leakage of a gas well.

Causality analysis, beyond “mere” correlations, has become increasingly important for scientific discoveries and policy decisions. Many of these real-world applications involve time series data. A key observation is that the causality between time series could vary significantly over time. For example, a rain could cause severe traffic jams during the rush hours, but has little impact on the traffic at midnight. However, previous studies mostly look at the whole time series when determining the causal relationship between them. Instead, we propose to detect the partial time intervals with causality. As it is time consuming to enumerate all time intervals and test causality for each interval, we further propose an efficient algorithm that can avoid unnecessary computations based on the bounds of F-test in the Granger causality test. We use both synthetic datasets and real datasets to demonstrate the efficiency of our pruning techniques and that our method can effectively discover interesting causal intervals in the time series data.