Nephogram Analysis And The Cloud Area Measurement Based On Image Processing Technology

The study on the technology and methods for clouds classification and clouds analysis prediction, and the research on how to identify nephogram and estimate clouds regional objectively, precisely and timely, which are main research directions in the application technology on the meteorology. Based on cross-ideologies of disciplines and methods, this paper explores on nephogram analysis and clouds area measurement by using digital image processing technology and provides effective algorithm in the process of analysis and measurement.This paper first pre-treat nephogram and presents a new method of removing underlying surface——pad-histogram threshold value method of twin peaks. This method will make use of different gray-level between sample cloud and underlying surface in the picture to realize sample cloud and underlying surface segmentation efficiently. As for wiping off mist noise, homomorphic filtering method is used because the mist change is relatively flat, corresponding to the low frequency components. Experiment shows that pre-treat nephogram quality is improved while complexity lowered, a better image effect。After image pre-treatment, the paper carried out further analysis of the sample cloud in this chapter. First, aiming to solve the dimension disasters problems brought by the traditional PCA, this paper gives the advanced algorithm of PCA, reduces the mean-square-error in non-compressed and compressed situations and improves the resolution in order to obtain clear sample nephogram in low dimension space of digital image. Experiment shows that the image SNR increase by7.64dB and the image recognition rate also largely improved.The paper also discussed the quantitative statistics of the sample cloud, giving the basic ideas and realization of functions of count. The algorithm is run in MATLAB, the simulation results not only count the same, but also operation is very simple, time-saving when it compares to the traditional manual. Finally, according to the current situation of sample cloud Reflectance measurement, this paper combined image processing techniques and mathematical theory organically, established mathematical relationships between the reflectivity, visual light and infrared brightness, achieving the purpose of the sample cloud classification.In addition, satellite nephogram exists more or less "blind area" of cloud cover causing information lost which harm nephogram analysis and interpretation. This brings up a second question in this paper to solve——calculating clouds area. Making the image of N*M element in array into a set of blocks made of many non-overlapping regions. Using image processing technology will improve Freeman chain code algorithm, only judgying the boundary points of the chain code, achieving the rapid filling of the enclosed area in order to calculate the area of irregular clouds automatically. The experimental results show that the computing time-consuming small, accuracy achieves about±1%.In short, this paper presents effective and feasible solution for nephogram analysis and clouds area measurement by using image processing technology. The findings is based on previous theories, optimized and improved by this paper, providing new ideas for future theory study and application.