Toshiro Sugimura

Flood–drought cycle of Tonle Sap and Mekong Delta area observed by DMSP‐SSM/I

A method for the linear estimation of water surface area within a land domain in the tropical region of Tonle Sap and the Mekong Delta is studied using special sensor microwave/imager (SSM/I) data. The coefficient of correlation between the water area estimated by SSM/I and that estimated by AVHRR falls within a range of 0.97–0.99, when 37 GHz horizontal polarization (Hpol) brightness temperature TB data is applied to the SSM/I data. This implies that observation by SSM/I has practical applications in flood monitoring in tropical regions. We have also verified a method for linear estimation of water area within a pixel, utilizing the difference of emissivity between SSM/I 37 GHz Hpol and vertical polarization (Vpol) data. This estimation shows good secondary correlation with the first method. Values of water area obtained in the dry season appear somewhat larger than those from the NOAA/AVHRR data. Applying the first methodology, a transition of water cover area over Tonle Sap and Mekong Delta was plotted from May 1997 to April 1999. The transition patterns in both watersheds synchronize well with the transition patterns of precipitation in the region. A phase shift of flood–drought cycles of Tonle Sap and Mekong watersheds can be observed. Flooding in the Mekong Delta watershed begins to subside one and a half months after that in the Tonle Sap watershed starts. Fluctuation of the water area of the Mekong Delta synchronizes with that of the water level in the Mekong Delta.

Improvement of forest type classification by SPOT HRV with 20 m mesh DTM

Abstract For multispectral analysis of forest land in mountainous areas, the estimation of true reflectance without the terrain having an effect on the sensor response is indispensable. To study this subject, the authors carried out the following experiment. First, we made a precise digital terrain model (DTM) at an interval of 10 m for a test forest site covered with Lambertian-type crown surface. Analysing the forest land from the SPOT data with the precise DTM, we obtained a classification result of forest type about 20 per cent higher accuracy than the result without application of this method.

Analysis of landuse change in periphery of Tokyo during last twenty years using the same seasonal landsat data

Abstract Urbanized areas are growing rapidly with the concentration of city functions and the increment of population, and the natural environment has been deteriorating. This paper reports the increasing urbanization occurring through changes in landuse, population, and land price in Japans national capital city, Tokyo, during the past twenty years. Selecting the capital city and the periphery of Tokyo as the test region, the areas within this region were classified according to the distance from the center of Tokyo and the access to the capital city by train. The landuse change for each area can be characterized according to the classification of artificially developed areas, areas of vegetation cover and others. The process of urbanization in the capital city of Tokyo is further discussed.

JAXA High Resolution Land-Use and Land-Cover Map of Japan

Japan Aerospace Exploration Agency creates the “JAXA High Resolution Land-Use and Land-Cover Map (JHR LULC Map)” in Japan. The data was acquired by the Advanced Visible and Near Infrared Radiometer type 2 (AVNIR-2), onboard the Advanced Land Observation Satellite. Ortho-rectification, atmospheric and slope correction were applied to the AVNIR-2 data. The number of the input data for the classification is 1,876 scenes which were acquired from April 28, 2006 to April 15, 2011. The classification categories are 1) water, 2) urban, 3) paddy, 4) crop, 5) grass, 6) deciduous forest, 7) evergreen forest, 8) bare land, and 9) snow and ice. Pixel spacing of the JHR LULC Map is 0.000278° and 0.000333° for the latitude and longitude, respectively. The temporal classification accuracy was found to be 89.3%, which was calculated using the validated accuracy of the classification multiplied by the surface ratio in each category by the Ministry of Internal Affairs and Communications.

Surface currents around Hokkaido in the late fall of 1981 obtained from analysis of satellite images

This paper describes the characteristics of currents around Hokkaido using a current vector map compiled by chasing the displacement of sea marks on a pair of successive thermal infrared images taken from a satellite, NOAA-6. The points of some sea surface patterns showing distinctive features which can be commonly identified in both images are called “Sea Marks≓. This “sea mark chase method≓ has a great advantage over velocity measurements by boats or buoys, in that it gives a synoptic view of the velocity distribution over a broad sea area extending for some hundreds of miles on a short time scale of half a day.In order to investigate the current in the late fall of 1981, we used the data taken at 19:05 JST on 30 October and at 7:20 JST on 31 October. With these data taken with a 12 hr difference, the measurement accuracy of the speed of sea marks reached ±0.1 knot through geometrical correction. The velocity vectors of sea marks agreed with results of GEK measurements performed on those days, and also with the mean current pattern obtained in the past based on sea surface data.The most distinct features recognized were some cyclonic and anticyclonic eddies of the order of 100 km in diameter which dominated in the Kuril Basin of the Okhotsk Sea. They appeared clearly in the original NOAA images and their physical parameters were determined quantitatively from the vector map. These eddies were located in the region of decay of the Soya Warm Current and were rotating at a speed nearly as large as that of the current. The problems of what feeds energy to these eddies and how long they live remain to be solved in future studies.

Water surface area measurement of Lake Volta using SSM/I 37-GHz polarization difference in rainy season

Abstract The objective of this study is to examine the possibility of measuring the area of Lake Volta using DMSP-SSM/I data. In the method 1, using the difference between 37-GHz data of water surface and of the ambient land, stable values for three years in the rainy season are obtained. The difference between 37-GHz Vpol values and that of 37-GHz Hpol fluctuates slightly. Although we could not obtain the truth data due to cloud cover over the area in the rainy season, data obtained from NOAA/AVHRR and ETOPO5 elevation provide a means to evaluate the result from the SSM/I data.

Digital roof model (DRM)using high resolution satellite image and its application for 3D mapping of city region

In urban area artificial structures are built over crowdedly and show their complex three-dimensional (3D) characteristics. The authors create a concept of digital roof model (DRM) for giving a series of height of buildings roofs in urban area retrieved from a pair of high resolution images from satellites as IKONOS or QUICKBIRD. They develop consequently an automatic method to generate a DRM. Three-dimensional data of topography of the ground has been expressed mainly with the contour lines or the digital elevation model (DEM) obtained from aerial photographs so far. The contour lines or the DEM show the elevation of ground surface. In order to express correctly the detail of urban space structure, however, single data of ground elevation cannot be said enough. Thus the authors tried making an algorithm to obtain the roof elevation of buildings from high resolution satellite data. Two DRMs were generated for two urbanized areas concentrated with lower buildings and with taller buildings. The accuracy of the DRM was compared with the truth data. Differences between both heights of buildings by the truth and the DRM value became 5.2m rms. Fusing IKONOS spectral data and DRM product, a 3D birds-eye view of the city region is presented. Though it shows a certain quality of reproducibility of the 3D structure, more improvement of DRM is required. Key word - Digital Roof Model (DRM), Birds-eye view, High resolution9y Urban environment

Analysis of hydrological changes in Lakes of Asian arid zone by satellite data

This paper describes a method and results for the investigation of the recent hydrological changes in Aral Sea and Lake Balkhash of Central Asia using multi-temporal satellite data. Landcover change of the lakes and their vicinity from 1960s to 1990s were analyzed by comparing the landcover classification images. Using the analyzed satellite images, a bathymetric map and the meteorological observations, change estimation of water volume and levels, and analysis of water balance in lakes were carried out. It is presumed that the change in Aral Sea has been affected by human activities. Contrary to this, the change of lake Balkhash has been affected by both human and natural dimensions.

An application of digital roof model (DRM) for height measurement of trees

Three dimensional data of forest structure provided by measurement of tree height fulfils an important role to nurture the forest and to conserve its environment. The authors have advanced the investigation of three-dimensional information of a city area by using high resolution satellite images. This image succeeds in providing three-dimensional descriptions of building roofs in the city area by the digital roof model (DRM). DRM is the half side of twin data expressing the ground surface and the tree canopy surface. The ground data are expressed by the digital terrain model (DTM). Measuring the coordinates of corresponding same points on a pair of the high resolution satellite image observed from different orbits, the DRM of forest, i.e. the canopy surface height can be made. Choosing trees in a city park experimentally, a DRM was generated. The shape of the canopy surface accords with the height of the trees obtained by ground surveying.

Pinatubo volcanic dust diffusion into the stratosphere seen from space

Abstract GMS-4/VISSR and NOAA-10/AVHRR data of Mt. Pinatubo area taken on June 15, 1991 reveal an aspect of the stratospheric diffusion of erupted volcanic dust. Erupted dust or Gasses reached a height of about 34 km above sea level. The eruption continued about 8 hours from 6Z to 15Z of June 15, 1991. Scale of the dust diffusion pattern grew up to a size about 600 km in diameter in south-north direction. At the beginning stage to the big eruption, a series of eruptions occurred but those scale was rather smaller than that of the latter big eruption.