IMPROVEMENT OF THE METHOD TO ESTIMATE RELATIVE NIGHT-TIME CITYLIGHT INTENSITY OF THE HIGHLY URBANIZED AREA CONSIDERING THEFLUCTUATION OF OBSERVED DIGITAL NUMBER IN DMSP VISIBLE IMAGERY

摘要

Night-time city light distribution observed by DMSP satellites has been focusedrnon as a promising approach to monitor the global human activities. Highly urbanized area is, however, easily saturated since its intensity of night-time city light is larger than the gain limit of DMSP visible band sensor in routine observation. This make it difficult to estimate basic in-formation required in disaster risk assessment such as distribution of population and social in-frastructures in highly urbanized area. In this paper, we proposed an improved methodology to estimate the original median of DN values which should have been obtained without upper gain limit on a pixel during given period as an index of relative night-time city light intensity con-sidering the stability of probability distribution of DN values. It was clarified that relative cityrnlight intensity (RCI) based on improved methodology is superior to RCI based on precedingrnmethodology proposed by Takashima and Hayashi (2004) as an index of night-time city lightrnintensity and that improved RCI is more advantageous than preceding RCI in estimation ofrnpopulation especially in highly urbanized area.