Ali akbar Shamsi pur; Kazem Alavi panah; Hossein Mohammadi
Volume 17, Issue 3 , October 2010, , Pages 445-465
Abstract
The purpose of this study is to track and analyze the environmental effects of droughts by remote sensing indices in Kashan desert and dry zone. Temporal changes of droughts was evaluated using normal Z index in annual and seaonal (spring) scales. Spectral and thermal data from data series of NOAA-AVHRR ...
Read More
The purpose of this study is to track and analyze the environmental effects of droughts by remote sensing indices in Kashan desert and dry zone. Temporal changes of droughts was evaluated using normal Z index in annual and seaonal (spring) scales. Spectral and thermal data from data series of NOAA-AVHRR satellite between 1998 and 2004 were used to determine the drought indices. Vegetative and thermal drought indices were calculated using NDVI, VCI and TCI values derived from NOAA-AVHRR data. Results from applying mentioned indices showed that this area had low vegetation index values as NDVI index was generally less than 0.2. According to NDVI and VCI maps, years of 2000 and 2001 were characterized as drought condition contrary to 2002 and 2004 as rainy years.However, land surface temperature (LST), TCI and VHI indices showed different temperature conditions specifically in the months of April and May. Using validation of results derived from remote sensing indices, test of significance between them and climatic indices was calculated.According to the calculations, climatic condition of the study area was more compliant with the results of vegetation indices. Also thermal condition of the environment was more accurately indicated by thermal indices. According to the results, applying remote sensing data in environmental studies of arid and desert regions like Kashan is recommended.
Hamid reza Matin far; Kazem Alavi panah; Ammar Rafiei Emam
Volume 16, Issue 4 , January 2010, , Pages 560-573
Abstract
One of the apparent characteristics of soil is color which shows high correlation with soil characteristics and spectral reflectance. Soil color is identified using visual comparison of sample and colored chips of Munsell color charts .In arid regions due to the prolonged sunny days, low soil moisture, ...
Read More
One of the apparent characteristics of soil is color which shows high correlation with soil characteristics and spectral reflectance. Soil color is identified using visual comparison of sample and colored chips of Munsell color charts .In arid regions due to the prolonged sunny days, low soil moisture, sparse vegetation cover and close relation between land units and soils, there is an ideal condition for application of remote sensing data especially for study of relation between satellite data and color of surface features. The soil color and the most effective factors on color and spectral reflectance of soil are explained in brief. Color composite images produced from TM7, TM4 and TM2 as red, green and blue respectively used in order to choose sample sites. The 20 sample sites were chosen based on resample 3×3 pixels (90×90 m). In each site, the soil surface conditions and the munsell color of the soil surface were investigated in the field. Some physico-chemical properties of soil samples were also determined in the laboratory. The results of this study indicates that munsell notation of hue, value and Chroma are significantly correlated to the visible bands of Landsat (TM) data. From this study it may be concluded that visible reflectance of Landsat can be used to estimate soil color, if very precise result is not expected .More investigation are necessary in order to improve the obtained results.
Ammar Rafiei Emam; Kazem Alavi panah
Volume 13, Issue 1 , February 2006, , Pages 1-9
Abstract
Remote sensing plays a considerable role on detection of natural resources features by its multi spectral means. Three decades works of remote sensing scientists have resulted in presentation of several vegetation indices, for soil how ever there are not many examples. TM spectral ratioing have been ...
Read More
Remote sensing plays a considerable role on detection of natural resources features by its multi spectral means. Three decades works of remote sensing scientists have resulted in presentation of several vegetation indices, for soil how ever there are not many examples. TM spectral ratioing have been employed in this study to overcome problem of detection of soil variation. To reach the point spectral ratioing of TM (18 May 1998) was used. Data used in this study were: a) 3 first principle component, b) spectral ratioing of reflectance bands, c) spectral ratioing of Thermal band and d) original bands of TM. Results show that distinction of different soil in possible by PC3 on the basis of soil moisture variation. So, more researches in various regions for more studies in this subject are advised.