DMSP全球夜間映像の作成と夜の光分布に関する地理学的考察

抄録

Earth's surface lights observed from satellite indicate various aspects about artificial and natural phenomena. Major patterns of light distribution are caused from human activities in cities, forest, farmland, ocean, oil field, etc.
Global assessment of light distribution is important for us to investigate the state of natural environment on the Earth's surface and its change with human activity.
First, gathering 38 DMSP night light photographs in 1984 to 1988, a DMSP global nighttime image was created. Source data were DMSP Block-5D satellite films stored at Colorado University, a branch of World Data Center A. Thanks to the staffs of the University, cloud free or almost less data could be obtained.
Second, a compilation process was taken by A/D conversion from photographs to digital data. After taking two processes, radiometric and geometric correction, a global scale image was produced. Ground control points were used for regional film orientation, and resampling and mosaicking processes were taken.
Our final approach was an interpretation of geographical meaning of the night light in global scale, specially with human activities. We summarized our idea as follows.
1) DMSP nighttime images with selected GCPs about 14 to 41 points after radiometric correction were oriented to a plate carree coordinates by three cubic polynomials. The registration accuracy was about 1.0 pixels and 1.0 lines.
2) A DMSP global nighttime image could be produced by resampling and mosaicking operations on plate carree coordinates. It was proved that the geographical position and the range of light distribution could be investigated in detail on the image combining both of the GVI data and the geographical information.
3) Relationship between light distribution and the human activity was investigated.
4) It was clearly shown that the distribution patterns of light based on sifting cultivation were located in forest of mountainous district and savanna zone.
5) It was searched that the both fishing fire and the flare of oil field had the regional feature.
6) The light distribution pattern on the nighttime image is a description of natural energy consumption. It is thought that the influence of human activity for the natural environment can be investigated from this new viewpoint, if detailed analysis of the nighttime image could continuously be done with the other auxiliary sources.