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21.
Meiyan Shu Xiaohe Gu Lin Sun Jinshan Zhu Tingting Chen Kai Wang Quan Wang Guijun Yang 《遥感技术与应用》1986,35(1):194-201
The GaoFen4 (GF4) satellite is China’s first geo-synchronous orbit remote sensing satellite. With the advantages of high frequency and wide width, it can provide fast and stable optical remote sensing images for agricultural, forestry, disaster reduction, meteorology, environmental protection, water conservancy and other applications in China. Efficient image automatic cloud detection helps to further improve the utilization efficiency of GaoFen4 images. CDAG(Cloud Detection Algorihtm-Generating)Cloud detection is an automatic cloud detection algorithm based on spectral analysis of pixel components, which can effectively reduce the influence of mixed pixels, complex surface structure and atmosphere. This paper aims to explore the application of CDAG algorithm in cloud detection of GaoFen4 multispectral imagery (GF4-PMS). Firstly, different cloud types and surface cover types were selected from hyperspectral images (AVIRIS) to establish cloud pixel library and clear sky pixel library. Next, the pixel library of multispectral images was simulated based on Hyperspectral pixel library and spectral response function of GF4-PMS sensor. Then, according to the spectral difference analysis of broken cloud, thin cloud, thick cloud and non-cloud pixel, the similarity probability analysis was performed on the to-be-detected pixel of the GF4-PMS image and the terminal pixel, and the GF4-PMS image cloud detection based on the optimal threshold automatic iteration was realized. Finally, cloud detection accuracy verification was carried out from multiple indicators such as cloud pixel correct rate, clear sky pixel correct rate, false positive rate and missed rate. The results show that AVIRIS images can effectively extract terminal pixel libraries for GF4-PMS image cloud detection. Clouds of Various types on GF4-PMS images can be better identified based on the CDAG algorithm. The accuracy of detection results for broken clouds, thin clouds and thick clouds with different time phases and different underlying surfaces can reach more than 90%. Therefore, the cloud detection method based on the priori terminal pixel library has a good application value for improving the utilization efficiency of GF4-PMS images. 相似文献
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剖析了时间延迟积分CCD(TDICCD)像元校正对信噪比和调制传递函数测试的影响,设计了基于辐射标定和地面控制的多通道TDICCD像元响应非均匀性实时处理方法以提高星上实时图像的像元响应非均匀性。该方法基于辐射标定去除图像的固定图形噪声,并校正图像奇异点;通过分析星上实时传输图像,处理奇异点像元的图像问题,实现地面控制像元响应非均匀性的实时调整。提出的系统实时处理方式可以不改变硬件结构即有效改善图像的视觉效果,对于坏像元、像元性能降低、像元污染等特定情况有很强的纠错能力。实际成像试验的对比表明,该方法对信噪比、调制传递函数有很好的修正作用,其精确调整能力分别达到0.1db及0.01;在50%饱和值下测试的图像非均匀性指标达到1.25%。该方法结构简单,在工程实践中有很好的应用前景。 相似文献
23.
To improve poor viewing angle characteristics of top emission organic light emitting diodes (TEOLEDs) without any serious pixel blur phenomena, we applied a circular polarizer (CP) film modified by nanoporous polymer film (NPF). From this approach, we could improve the color shift significantly (Δu'v’ in CIE 1976 with viewing angle, from 0.0165 to 0.0114), and expand angular light emission distribution of off-axis by applying CP with NPF. We found that black color shift was little associated with NPF position change although black color was slightly faded tint by applying NPF, as like plasma display panel(PDP)’s off condition. Very interestingly, we found that the reflectance was not changed seriously whether NPF exists between glass encapsulation and CP or not. Besides, we investigated the pixel blur level when we applied different condition in encapsulation thickness and morphology of diffusing films. As a result, we found that the pixel blur phenomena can be significantly suppressed by applying thin encapsulation and NPF type diffuser film. 相似文献
24.
Sushmita Mitra 《Information Sciences》2011,181(17):3601-3613
Satellite images often require segmentation in the presence of uncertainty, caused due to factors like environmental conditions, poor resolution and poor illumination. Since any subsequent image analysis depends on the quality of such segmentation, one has to obtain an efficient algorithm for the purpose. Pixel clustering is a popular way of determining the homogeneous image regions, corresponding to the different land cover types, based on their spectral properties. In this paper we map the newly developed shadowed clustering algorithm to the problem of segmenting remotely sensed images.It is observed that shadowed clustering can efficiently handle overlapping among segments while modeling uncertainty among the boundaries. Unlike rough clustering, here the choice of user-defined parameters is fully eliminated. The number of segments is automatically optimized in terms of validity indices. The algorithm is robust in the presence of outliers. The superiority of the system is demonstrated in segmenting a synthetic image, along with land cover types from the Indian Remote Sensing (IRS) images of the cities of Mumbai and Kolkata and the SPOT image around Kolkata. The algorithm is found to efficiently and accurately extract the different homogeneous regions in the presence of uncertainty. The results are analyzed both qualitatively and quantitatively. 相似文献
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Further computer results are presented on the use of Fisher's linear discriminant for pixel classification in object isolation of infrared images. A new form of theoretical error probability is proposed which compares very favorably with the experimental error probability. 相似文献
30.
Vladimir A Kovalevsky 《Pattern recognition letters》1984,2(5):281-288
For all kinds of stationary plane grids only the 6-neighborhood is consistent. It admits the definition of a digital curve, in particular a contour, as a set of pixel pairs. Thus curves become objects of zero thickness and may be coded with one bit per grid step. 相似文献