A hazardous noxious substance (HNS) spill accident is one of the most devastating maritime disasters as it is accompanied by toxicity, fire, and explosions in the ocean. In this study, a ground HNS measurement experiment was conducted for artificially spilled HNS by using two hyperspectral cameras at VNIR and SWIR wavelengths. HNS images were obtained by pouring 1 L of toluene into an outdoor marine pool and observing it with a hyperspectral sensor installed at a height of approximately 12 m. The pure endmember spectra of toluene and seawater were extracted using principal component analysis and N-FINDR, and a Gaussian mixture model was applied to the toluene abundance fraction. Consequently, a toluene spill area of approximately 2.4317 m2 was detected according to the 36% criteria suitable for HNS detection. The HNS thickness estimation was based on a three-layer two-beam interference theory model. Considering the detection area and ground resolution, the amount of leaked toluene was estimated to be 0.9336L. This study is expected to contribute to the establishment of maritime HNS spill response strategies in the near future based on the novel hyperspectral HNS experiment.
As marine traffic has increased, the importance of ship detection using remote sensing images has been emphasized. Especially, with a better performance for discrimination of target, the usage of hyperspectral data for marine surveillance has been increasing recently. In this study, we detected the vessels on airborne hyperspectral images and quantitatively analyzed the detection results. To obtain the airborne hyperspectral images and auxiliary data for the quantitative validation, the in-field airborne imaging experiment was carried out. In addition, four different end-member extraction techniques including N-FINDR, PPI, ICA, and VCA were applied for comparison of detection performance with hyperspectral unmixing methods. Detection results present significant differences by endmember extraction techniques. The N-FINDR and VCA techniques presented a total of 14 vessels, while the ICA technique detected seven vessels, and the PPI technique detected two vessels. The pixel-based probability of detection and false alarm ratiofor all 14 ships were 98.83% and 4.30%, respectively. This study also addressed the important role of abundance fraction analysis for marine surveillance purpose.
Characteristics of speckle errors of Sea-viewing Wide Field-of-view Sensor (SeaWiFS) chlorophyll-a concentration
were analyzed, and its removal process was presented in the East Japan Sea from September 1997 to December 2007.
Level-3 data of SeaWiFS chlorophyll-a concentration provided by NASA showed significant speckle errors in the East
Japan Sea. The speckles with anomalously high concentrations were randomly distributed and showed remarkably high
bias, compared with their neighboring pixels. The speckles tended to appear frequently in winter, which might be related
to cloud distribution. Ten-year averaged cloudiness of winter was much higher over the southeastern part, with frequent
speckles, than the northwestern part of the East Japan Sea. Statistical analysis results showed that the number of the
speckles was increased as cloudiness increased.
Herein, we present a methodology of how to remove the speckles with highly anomalous chlorophyll concentration
data using Level-2 data and how to composite the chlorophyll-a data to generate Level-3 data. Considering seasonal
variations of the speckles and their statistical characteristics, dynamic threshold methods were given. Additional
methodology for high values during spring bloom was also developed by considering the chlorophyll-a concentration
frontal zone. After applying the methodology to ten-year Level-2 data, data composite of Level-2 was carried out to
produce Level-3 product and compared with the NASA product. The results showed that most speckles were disappeared
and more than 10% errors of 5°×5° mean values were reduced at speckle regions in the southeast East/Japan Sea.
This study raised the issue about speckle errors in chlorophyll-a concentration composite from SeaWiFS data in the
East Japan Sea for the first time and presented regionally-optimized composite method for more reliable chlorophyll-a
data in oceanic application researches.
Relation between the spring bloom along the Primorye coast and sea ices of the Tatarskiy Strait in the northern
East/Japan Sea were investigated using ten-year SeaWiFS chlorophyll-a concentration data and sea ice concentration
data DMSP/SSMI for the period of 1998~2007. Year-to-year variations of chlorophyll-a concentration in spring were
positively correlated with those of sea ice concentrations at the Tatarskiy Strait in the previous winter. Abrupt increases
of nutrients, indispensable for spring bloom at the upper ocean in spring, were supplied from sea-ice melted waters. The
water mass from sea ices provided a preferable condition for the spring bloom through changes in vertical stratification
structure of water column. Along-coast ratios of stability parameters between the two neighboring months clearly show
rapid progress of generation of shallow thermocline due to the ice-originated fresh waters.
Twenty-year Normalized Difference Vegetation Index (NDVI) data on the highest mountain in northeast Asia were
analyzed to understand their temporal variability and response to large-scale El Niño-Southern Oscillation (ENSO)
events. We demonstrated the first unequivocal evidence that El Niño events have played an important role in determining
the ecosystem conditions in the Mt. Baekdu area in northeast Asia. The analysis confirmed that the onset of phenological
spring was earlier during ENSO years. This was evident from a negative trend of -0.5158 month per ENSO index
between year-to-year variations in spring timing and those in ENSO magnitudes. Over two decades, the phenological
phases were negatively correlated with air temperature variations under atmospheric warming at Mt. Baekdu. However,
such changes in NDVI are not likely to be affected by changes in the local precipitation, as inferred from forest types
determined by land cover classification. On the basis of changes in air temperature during ENSO years, the results of this
study indicate a significant remote connection between the local ecology at the highest mountain and the large-scale
atmospheric and oceanic phenomena.
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