It is important to understand the flow of marine debris for environmental research purposes, since marine debris causes extensive damage to coastal environments. Due to its small size, most marine debris in the ocean cannot be confirmed directly, even when a high-spatial-resolution satellite image is used. Thus, to extract candidate pixels containing possible marine debris, pixels with spectra that differ from those of the surrounding ocean are identified. As a first step towards identifying and monitoring marine debris, a method using spectral angle mapper (SAM) algorithm in n-dimensional space corresponding to the satellite spectral bands was previously proposed. In this paper, a method to discriminate marine debris from white-crested waves is proposed using the distance from the origin in an n-dimensional scatter diagram. Moreover, it is also discussed that the relationship between the distance from the coast and the amount of marine debris depends on the locations of the sea currents and neighbouring rivers.
The flow of marine debris in the Sea of Japan causes extensive damage to coastal environments. It is important to understand the debris flow in the ocean for environmental research. The small size of most marine debris in the Sea of Japan makes it impossible to be confirmed directly, even when using high-spatial-resolution satellite imagery. Thus, to extract candidate pixels containing possible marine debris, pixels with spectra that differ from those of the surrounding ocean and wave crests were identified. As a first step towards monitoring marine debris, a previously proposed method for identifying marine debris floating in the Sea of Japan uses a histogram showing the distance from the regression line of the scatter diagram of satellite spectral bands. In this paper, a new method using a spectral angle mapper (SAM) in four- or eight-dimensional space corresponding to satellite spectral bands is proposed. The validity of the method using SAM is also discussed.
The flow of marine debris in the ocean causes extensive damage to coastal environments. In addition to local rivers, a
large proportion of the marine debris that washes up along the coastline of the Sea of Japan originates in neighboring
countries. It is considered important to understand the flow of marine debris in the Sea of Japan for environmental
research purposes and for international relations. This study describes the results of monitoring marine debris flows
using multi-spectral satellite images. The small size of most marine debris means that it cannot be confirmed directly,
even when using high spatial resolution satellite imagery. Thus, to extract candidate pixels containing possible marine
debris, pixels with spectra that differ from those of the surrounding ocean and the wave crests were identified. As a first
step towards monitoring marine debris, a method for identifying marine debris floating on the Sea of Japan has been
proposed using two-dimensional scatter diagrams of satellite spectral bands.
The 2011 off the Pacific coast of Tohoku earthquake (Mw = 9) was one of the most devastating earthquakes in
Japanese history. The extremely large and widespread tsunami it generated caused a large amount of debris to flow into
the Pacific Ocean. It is important to understand debris flow in the ocean for both environmental research and
international relations. In this study, tsunami debris was monitored by satellite remote sensing. As a first step, we
propose a method for identifying debris floating on turbid sea areas through thin clouds using two-dimensional scatter
diagrams for MODIS spectral bands. Characteristic regions in the images are effectively separated by using the scatter
diagram to identify six regions (land, coastal areas, debris, cloud, turbid sea, and clear sea). We report initial results of
monitoring debris floating in the Pacific Ocean.
The purpose of this study is to develop an algorithm for estimating the chlorophyll-a concentrations of relatively clean
coastal waters and highly eutrophic lakes from multispectral satellite images (ALOS/AVNIR-2) and field survey data.
Obama Bay has a low chlorophyll-a concentration (<10 mg/m3). In contrast, Lake Kitagata is a brackish, eutrophic lake
that is connected to the Japan Sea in the northeast, and it has a chlorophyll-a concentration in the range 10 to 200 mg/m3.
For both water areas, the correlation coefficients between various ratios of satellite spectral bands and field survey data
are calculated to determine the most suitable algorithm for estimating chlorophyll-a concentration.
The preliminary results indicate that an algorithm using visible bands (bands 1, 2, and 3 for ALOS/AVNIR-2) have
high correlation coefficients for Obama Bay, whereas an algorithm using the near-infrared band (band 4) is suitable for
Lake Kitagata when it is highly eutrophic. These results indicate that water with a low chlorophyll-a concentration has a
low near-infrared spectral reflectance, because of the strong absorption of light by water in near-infrared wavelengths.
The purpose of our research is to develop the procedure to extract the information on water quality of Lake Kitagata
(heavily eutrophic lake), from multi-spectral satellite images. As the first step of our research, the controlled experiment
in the laboratory, measuring the spectral reflectance of water of Lake Kitagata to search the principal components in it,
has been carried out. Preliminary results of the laboratory experiment indicate that the main components of the water of
Lake Kitagata are mud and plant including phytoplankton. Moreover, the results of the analyses for the direct sampling
data of Lake Kitagata obtained by local government of Fukui prefecture (Fukui Prefectural Institute of Public Health and
Environmental Science) are also reported.
Since June, 2004, studies on triggering factors of the red tide have been carried out in Awara Space Radio Observatory (ASRO), Fukui University of Technology utilizing directly received data of MODIS on the Terra and Aqua satellites which have been acquired in ASRO. Preliminary results of the data analyses for the period from July, 2001 to April, 2005 indicate conditions, for the appearance of the red tide bloom in Wakasa bay as follows: (1) the threshold amount of chlorophyll-a is close to 1.5mg/m3, (2) the range of sea surface temperature (SST) is limited in a range from 12 to 20oC and (3) the period of sunlit time in spring is also a significantly sensitive factor. We propose here to utilize MODIS band1 images corresponding to a red band with spatial resolution of 250m together with NDVI (Normalized Difference Vegetation Index) images which has also spatial resolution of 250m, for the confirmation of the red tide. The problem of coincidence between colored region due to SS (Suspended Sediment) and red tide region using only band1 of MODIS, has been solved by using NDVI images in addition to band1 images together as two dimensional diagram.
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