We have developed a method to monitor the slant column density of nitrogen dioxide in the lower troposphere using a compact hyperspectral camera with a high spectral resolution of 1 nm at the full width half-maximum. Measurements of skylight spectra were conducted in wavelength regions of 460-490 nm and 550-610 nm to retrieve the slant column densities of nitrogen dioxide, in addition to water vapor and oxygen dimer. The results of ground-based measurements are shown for the cases of urban air pollution and aircraft emission near an airport runway.
Small size object detection in vast ocean plays an important role in rescues after accident or disaster. One of the promising approach is a hyperspectral imaging system (HIS). However, due to the limitation of HIS sensor's resolution, interested target might occupy only several pixels or less in the image, it's difficult to detect small object, moreover the sun glint of the sea surface make it even more difficult. In this paper, we propose an image analysis technique suitable for the computer aided detection of small objects on the sea surface, especially humans. We firstly separate objects from background by adapting a previously proposed image enhancement method and then apply a linear unmixing method to define the endmember's spectrum. At last, we use spectral angle mapping method to classify presented objects and thus detect small size object. The proposed system provides the following results for supporting the detection of humans and other small objects on the sea surface; an image with spectral color enhancement, alerts of various objects, and the human detection results. This multilayered approach is expected to reduce the oversight, i.e., false negative error. Results of the proposed technique have been compared with existent methods, and our method has successfully enhance the hyperspectral image, and detect small object from the sea surface with high human detection rate, shows the ability to further detection of human in this study). The result are less influenced by the sun glint effects. This study helps recognizing small objects on the sea surface, and it leads to advances in the rescuing system using aircraft equipped HIS technology.
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