Influencia das Condicoes de Iluminacao Solar Nos Dados TM/Landsat (Influence of Solar Illumination Conditions on TM/Landsat Data)

摘要

Satellite imageries are subjected to change in tonality as related to both topography and sensing geometry changes along the year. How changes in solar incidence angle affects digital number on the reflective TM bands was studied. Irradiance on the surface is a function of: (1) annual change in solar zenith and azimuth; (2) annual changes in the Sun-Earth distance; (3) aspect and inclination of slopes. All those variables can be joined in the term cos beta which was used to express changes in the radiance on the Earth surface. Correlation between cos beta and digital number was run for 72 examples and 2 different Earth targets; bare soil and sugar cane. The hypothesis tested was that if cos beta was the only factor effecting digital number, there would be a very high correlation between them. The results showed the following trends: (1) digital numbers taken from the soil samples are more dependent on cos beta than sugar cane sample; (2) infrared wavelengths are more dependent on cos beta term than visible wavelengths. Results led to the conclusion that topography does effect digital number on TM Landsat data.