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21.
A long-term Global LAnd Surface Satellite (GLASS) data-set for environmental studies 总被引:1,自引:0,他引:1
《International Journal of Digital Earth》2013,6(6):5-33
Recently, five Global LAnd Surface Satellite (GLASS) products have been released: leaf area index (LAI), shortwave broadband albedo, longwave broadband emissivity, incident short radiation, and photosynthetically active radiation (PAR). The first three products cover the years 1982–2012 (LAI) and 1981–2010 (albedo and emissivity) at 1–5 km and 8-day resolutions, and the last two radiation products span the period 2008–2010 at 5 km and 3-h resolutions. These products have been evaluated and validated, and the preliminary results indicate that they are of higher quality and accuracy than the existing products. In particular, the first three products have much longer time series, and are therefore highly suitable for various environmental studies. This paper outlines the algorithms, product characteristics, preliminary validation results, potential applications and some examples of initial analysis of these products. 相似文献
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《International Journal of Digital Earth》2013,6(6):582-603
ABSTRACTPublic understanding of climate and climate change is of broad societal importance. However, misconceptions regarding reasons for the seasons abound amongst students, teachers, and the public, many of whom believe that seasonality is caused by large variations in Earth’s distance from the Sun. Misconceptions may be reinforced by textbook illustrations that exaggerate eccentricity or show an inclined view of Earth’s near-circular orbit. Textbook explanations that omit multiple factors influencing seasons, that do not mesh with students’ experiences, or that are erroneous, hinder scientifically valid reasoning. Studies show that many teachers share their students’ misconceptions, and even when they understand basic concepts, teachers may fail to appreciate the range of factors contributing to seasonal change, or their relative importance. We have therefore developed a learning resource using Google Earth, a virtual globe with other useful, weather- and climate-related visualizations. A classroom test of 27 undergraduates in a public research university showed that 15 improved their test scores after the Google Earth-based laboratory class, whereas 5 disimproved. Mean correct answers rose from 4.7/10 to 6/10, giving a paired t-test value of 0.21. After using Google Earth, students are helped to segue to a heliocentric view. 相似文献
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针对面阵影像与线阵影像之间存在的尺度、旋转等几何差异所导致的难以高效获得稳定可靠匹配点问题,该文提出了一种稳健的面阵影像与线阵影像匹配方法。算法分为3个阶段:(1)对影像进行尺度、旋转预处理,消除影像间的尺度和旋转差异;(2)用Harris算子提取特征点,进行逐层金字塔匹配,在最底层影像上进行最小二乘匹配获取精匹配点,利用随机抽样一致算法获取准确性较高的匹配点;(3)对准确性较高的匹配点分区,构建4块匹配区域,根据每块区域的匹配点计算重心,以此4块区域的重心作为匹配基准点和基准方向,重约束初始匹配结果。通过多组面阵影像与线阵影像数据实验结果,验证了该方法的可行性和有效性,可为后续空中三角测量及相关应用提供可靠的匹配点。 相似文献
24.
Global geospatial data from Earth observation: status and issues 总被引:1,自引:0,他引:1
ABSTRACTData covering the whole of the surface of the Earth in a homogeneous and reliable manner has been accumulating over many years. This type of data became available from meteorological satellites from the 1960s and from Earth-observing satellites at a small scale from the early 1970s but has gradually accumulated at larger scales up to the present day when we now have data covering many environmental themes at large scales. These data have been used to generate information which is presented in the form of global data sets. This paper will give a brief introduction to the development of Earth observation and to the organisations and sensors which collect data and produce global geospatial data sets. Means of accessing global data sets will set out the types of data available that will be covered. Digital elevation models are discussed in a separate section because of their importance in georeferencing image data as well as their application to analysis of thematic data. The paper will also examine issues of availability, accuracy, validation and reliability and will look at future challenges. 相似文献
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本文结合实例讨论了小地区平面控制测量中多条图根支导线测角中误差m角平的三种计算方法,其中方法二全面考虑多条图根支导线的测量误差,其计算测角中误差m角平的公式也是最值得推广的。按照方法二可计算出各条图根支导线的测站点圆周角闭合差是否超过±40″,各条支导线的角度闭合差fβj是否超过40 n1″,测角中误差m角平是否超过21.2″,由此可以判断测角精度是否合格,在测量工作中具有一定的实用性。 相似文献
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