平面影像到DQG像元的转换精度与效率分析

平面影像到退化四叉树格网(Degenerate Quadtree Grid,DQG)的转换是实现全球DQG无缝可视化建模的前提任务。以相交面积为权重,提出平面影像到球面退化四叉树格网的转换算法。实验利用4km分辨率256级灰度图像数据Wsiearth.tif和30m分辨率Landsat5 Level4遥感数据,详细对比分了平面影像到退化四叉树格网与平面影像到四元三角格网(Quaternary Triangular Mesh,QTM)的转换精度和效率。     

基于Matlab的地图投影程序设计

随着地理信息系统(GIS)的发展与应用,地图投影转换成为GIS软件是当前面临的一个主要问题。本文首先分析和阐述了Matlab的程序设计基础、图形用户界面及地图投影整体程序设计,然后结合Matlab的计算程序,实现了高斯投影正算与反算、高斯投影换带、高斯投影与UTM投影之间转换的计算。通过实例验证了程序的可行性,满足了工程需要,为基于Matlab的地图投影程序设计提供了重要的参考依据。     

椭球变换法建立地方独立坐标系的变形研究

在分析高斯投影变形的基础上,针对工程测量中的投影变形精度要求,阐述了3种椭球变换法建立地方独立坐标系的方法,给出具体的计算公式和参数选取原则。对3种椭球变换法进行软件设计,简化计算的工作量。并详细介绍如何求解这些参数和控制点坐标值,结合实例数据进行分析,得到不同方法建立地方独立坐标系的优缺点和适用范围。     

车载鱼眼图像的全景图拼接误差分析

针对车载鱼眼图像拼接过程中的"拼接缝"的问题,对拼接误差的来源及其理论模型进行了分析。通过对全景影像的拼接过程进行梳理,对拼接误差的来源进行了论证,并对误差的理论模型进行了详细推导。最后,结合实际车载鱼眼数据,通过在不同目标距离情况下进行全景图拼接实验,证实了实际拼接成像效果与根据理论模型推导所得的拼接缝的大小基本吻合,说明了该文所提出的理论模型的可靠性,从而为后续改善全景图像拼接效果提供了理论支持。     

投影寻踪法在建立积雪深度模型上的应用

针对融雪期积雪深度变化问题的高维非线性、非正态特点,利用投影寻踪法将积雪深度变化多指标问题转化为单一投影指标问题,采用遗传算法优化投影方向得出最佳投影值,最终得到对积雪深度变化影响较大的因子,实现在低维空间上反应积雪深度变化的目的。实例分析结果表明:影响积雪深度变化的各因素贡献力依次为:土壤地表温度净辐射空气温度土壤体积含水量风速空气相对湿度降水水汽压。通过建立MLP神经网络积雪深度模型表明:利用投影寻踪法提取的积雪深度主要影响因子是可靠的,且提取的主要影响因子为简化积雪深度模型提供理论依据。     

大椭圆线椭球高斯投影在高速铁路工程中的应用

为了减少东西走向长线工程中的控制点数据在进行高斯投影转换时需要频繁换带的问题,提出了一种方法,即以工程线路中心线或其附近的大椭圆线为中央子午线,建立大椭圆线椭球,根据非线性规划最优理论求出大椭圆线椭球参数,并对其进行椭球变换,然后以此新椭球为基础进行高斯投影。     

全球气候变化的几个关键问题辨析

基于对全球气候变化事实与国家气候变化行动的分析,就当前全球气候变化科学认识和行动中的几个关键问题的不同观点与争论进行了辨析。指出：①应以比较确定的科学事实和“共同但有区别的责任”作为应对气候变化的出发点;②全球增温的幅度被高估了;③近百年全球变暖主要归因于人类活动的论断科学证据不足;④全球变暖的影响有利有弊,具体问题需具体分析;⑤气候预估不等于气候预测,气候预测尚待时日,气候预估的不确定性也非常大;⑥当前应对全球变暖的行动应采取“适应为主、减缓为辅”的战略。     

Climate Simulation and Future Projection of Precipitation and the Water Vapor Budget in the Haihe River Basin

The climatological characteristics of precipitation and the water vapor budget in the Haihe River basin (HRB) are analyzed using daily observations at 740 stations in China in 1951-2007 and the 4-time daily ERA40 reanalysis data in 1958-2001. The results show that precipitation and surface air temperature present significant interannual and interdecadal variability, with cold and wet conditions before the 1970s but warm and dry conditions after the 1980s. Precipitation has reduced substantially since the 1990s, with a continued increase of surface air temperature. The total column water vapor has also reduced remarkably since the late 1970s. The multi-model ensemble from the Fourth Assessment Report (AR4) of the Intergovernmental Panel on Climate Change (IPCC) has capably simulated the 20th century climate features and successfully reproduced the spatial patterns of precipitation and temperature. Unfortunately, the models do not reproduce the interdecadal changes. Based on these results, future projections of the climate in the HRB are discussed under the IPCC Special Report on Emissions Scenarios (SRES) B1, A1B, and A2. The results show that precipitation is expected to increase in the 21st century, with substantial interannual fluctuations relative to the models’ baseline climatology. A weak increasing trend in precipitation is projected before the 2040s, followed by an abrupt increase after the 2040s, especially in winter. Precipitation is projected to increase by 10%-18% by the end of the 21st century. Due to the persistent warming of surface air temperature, water vapor content in the lower troposphere is projected to increase. Relative humidity will decrease in the mid-lower troposphere but increase in the upper troposphere. On the other hand, precipitation minus evaporation remains positive throughout the 21st century. Based on these projection results, the HRB region is expected to get wetter in the 21st century due to global warming.     

温度升高和CO2浓度增加对冬小麦生物量的影响和不确定性分析（英文）

Impacts of climatic change on agriculture and adaptation are of key concern of scientific research. However, vast uncertainties exist among global climates model output, emission scenarios, scale transformation and crop model parameterization. In order to reduce these uncertainties, we integrate output results of four IPCC emission scenarios of A1FI, A2, B1 and B2, and five global climatic patterns of HadCM3, PCM, CGCM2, CSIRO2 and ECHAM4 in this study. Based on 20 databases of future climatic change scenarios from the Climatic Research Unit (CRU) , the scenario data of the climatic daily median values are generated on research sites with the global mean temperature increase of 1 ℃(GMT+1D), 2 ℃ (GMT+2D) and 3 ℃(GMT+3D). The impact of CO2 fertilization effect on wheat biomass for GMT+1D, GMT+2D and GMT+3D in China’s wheat-producing areas is studied in the process model, CERES-Wheat and probabilistic forecasting method. The research results show the CO2 fertilization effect can compensate reduction of wheat biomass with warming temperature in a strong compensating effect. Under the CO2 fertilization effect, the rain-fed and irrigated wheat biomasses increase respectively, and the increment of biomass goes up with temperature rising. The rain-fed wheat biomass increase is greater than the irrigated wheat biomass. Without consideration of CO2 fertilization effect, both irrigated and rain-fed wheat biomasses reduce, and there is a higher probability for the irrigated wheat biomass than that of the rain-fed wheat biomass.     

全球等面积四叉树离散格网建模与编码体系研究

在分析球冠、球带表面积公式的基础上,提出了一种等面积四叉树全球离散格网建模方法,阐述了格网划分机理,制定了格网编号体系,给出了由编号确定格网中心地理坐标及由地理坐标确定格网编号的公式,分析了其实际应用方向。