Xiao Pengfeng

Estimate of methane emissions from rice fields in China by climate-based net primary productivity

Rice fields provide food for over half of the world population but are also an important source of atmospheric CH4. Using the climate-based GIS empirical model and the meteorological data collected from 600 meteorological stations in China, with county as the basic unit, the net primary productivity (NPP) of rice fields in China in 1990, 1995, 1998, and 2000 were estimated to be in the range from 202.19×1012g C in 1990 to 163.46×1012g C in 2000. From the measured data of the factors affecting CH4 emission and NPP, the conversion ratio of the NPP into CH4 emission for the rice fields of China was determined to be 1.8%. Using this ratio and estimated NPP, the CH4 emissions from rice fields of China in 1990, 1995, 1998, and 2000 were estimated to be 7.24×1012, 6.31×1012, 6.77×1012 and 5.85×1012g CH4, respectively.

An investigation of urban water automatic extraction based on texture and imaging knowledge from high resolution SAR images

Extracting water body information with SAR images is distinctive and important. Especially for high-resolution SAR images, its hard to extract water accurately because of Speckle Noises, so a Gabor filtering method related to the image texture is proposed. Firstly, frequency spectrum analysis method was used to identify the wedge and ring characters of image texture, and the period and directional parameters of the texture distribution were computed. Based on these characters, Gabor filter were constructed in order to filter the frequency spectrum of the multi-texture image, and best filter parameters were selected. After the filtering in frequency domain, components of corresponding texture were acquired by transforming the filtered frequency spectrum image to time domain image. The test results of terra SAR image indicate that the water body extraction method is good.