GF-4卫星不同成像状态下影像定位误差特性分析   总被引：1，自引：0，他引：1  

韩杰  谢勇  李慧娜  苗宝亮  石宏斌 《测绘通报》2019,(8):59-62,67

高分四号（GF-4）卫星作为我国高分对地观测系统中一颗高分辨率面阵成像的静止轨道卫星，其在不同成像状态下的影像几何定位精度一直是科研人员和应用部门所关注的。本文以谷歌地球数据为几何参考，通过对比GF-4卫星影像和谷歌地球影像上同名点位置信息，分析了GF-4卫星在凝视、俯仰、滚动成像状态下的影像定位特性。结果表明，单幅影像内部均出现了明显的系统误差，凝视成像过程中同一点位的影像定位误差波动较小，俯仰/滚动姿态影像定位误差与俯仰角/滚动角成正比关系。该结论可为地面数据处理部门和用户在数据校正和应用时提供参考。  相似文献   

系缆式剖面测量平台运动性能分析     

李永军  董涛 《海洋技术学报》2008,27(1):11-13

文章简单介绍了系缆式剖面测量平台的结构构成,围绕剖面测量平台升降运动的工作原理,着重对平台的一些固有的基本特性所产生的影响进行了分析,供有关人员参考交流。  相似文献   

Retrieval Snow Depth by Artificial Neural Network Methodology from Integrated AMSR-E and In-situ Data —— A Case Study in Qinghai-Tibet Plateau     

CAO Yungang  ;YANG Xiuchun  ;ZHU Xiaohua 《中国地理科学(英文版)》2008,18(4):356-360

On the basis of artificial neural network （ANN） model, this paper presents an algorithm for inversing snow depth with use of AMSR-E （Advanced Microwave Scanning Radiometer-Earth Observing System （EOS）） dataset, i.e., brightness temperature at 18.7 and 36.5GHz in Qinghai-Tibet Plateau during the snow season of 2002-2003. In order to overcome the overfitting problem in ANN modeling, this methodology adopts a Bayesian regularization approach. The experiments are performed to compare the results obtained from the ANN-based algorithm with those obtained from other existing algorithms, i.e., Chang algorithm, spectral polarization difference （SPD） algorithm, and temperature gradient （TG） algorithm. The experimental results show that the presented algorithm has the highest accuracy in estimating snow depth. In addition, the effects of the noises in datasets on model fitting can be decreased due to adopting the Bayesian regularization approach.  相似文献   

图像端元全自动提取方法研究   总被引：1，自引：0，他引：1  

齐建成  朱述龙  朱宝山  赵泳  李二森 《海洋测绘》2009,29(2):16-19

传统端元提取算法一般需要人工指定端元数目，易导致多选或漏选端元。提出了一种端元全自动提取方法，通过研究分类结果的均方根误差、端元间光谱相关性与端元数目的关系，设置两种循环结束条件，当分类结果的均方根误差最小或端元间恰未出现强相关现象时，获得最佳端元数。实验表明，该方法是正确有效的，能够克服现有方法的不足，提高了端元提取自动化程度。  相似文献   

Hemispheric-scale climate response to Northern Eurasia land surface characteristics and snow anomalies   总被引：3，自引：0，他引：3  

Gavin Gong  Judah Cohen  Dara Entekhabi  Yan Ge   《Global and Planetary Change》2007,56(3-4):359

This paper presents a synopsis of recently published studies by the co-authors, which show that several land surface characteristics unique to Northern Eurasia are responsible for facilitating a causal relationship between autumn snow anomalies in this region and subsequent hemispheric winter climate patterns. The large size and extratropical location of the contiguous Eurasian land mass results in broad, continental-scale interannual snow cover extent and depth variations throughout autumn and winter, and corresponding diabatic heating anomalies. These surface anomalies occur in the presence of a large region of stationary wave activity, produced in part by the orographic barriers that separate northern/central Eurasia from southern/eastern Eurasia. This co-location of snow-forced anomalies and ambient wave energy is unique to Northern Eurasia, and initiates a teleconnection pathway involving stationary wave–mean flow interaction throughout the troposphere and stratosphere, ultimately resulting in a modulation of the winter Arctic Oscillation (AO). Complementary new results are also presented which show that partial snow cover extent or snow depth only anomalies in Northern Eurasia are insufficient to initiate the teleconnection pathway and produce a winter AO signal. This synopsis provides a useful interpretation of the earlier studies in the specific context of Northern Eurasia regional climate and environmental change.  相似文献   

A new temperature based method to separate rain and snow   总被引：2，自引：0，他引：2  

Stefan W. Kienzle 《水文研究》2008,22(26):5067-5085

This paper presents the development and testing of a new method to estimate daily snowfall from precipitation and associated temperature records. The new method requires two variables; the threshold mean daily air temperature at which 50% of precipitation is considered snow, and the temperature range within which mixed precipitation can occur. Sensitivity analyses using 15 climate stations across south‐western Alberta, Canada, and ranging from prairie to alpine regions investigates the sensitivity of those two variables on mean annual snowfall (MAS), the coefficient of determination, and the MAS‐weighted coefficient of determination. Existing methods, including the static threshold method, one linear transition method used by Quick and Pipes, and the Leavesley method employed in the PRMS hydrological modelling system are compared with the new method, using a total of 963 years of daily data from the 15 climate stations used for the sensitivity analyses. Four different approaches to using the two input variables (threshold temperature and range) were tested and statistically compared: mean annual variables based on the 15 stations, mean annual variables for each station, mean monthly variables for each station, and a sine curve representing seasonal variation of the variables. In almost all cases the proposed new method resulted in higher MAS‐weighted coefficients of determination, and, on average, they were significantly different from those of other methods. The paper concludes with a decision tree to help decide which method and approach to apply under a variety of data availabilities. Copyright © 2008 John Wiley & Sons, Ltd.  相似文献   

Open boundary conditions for nonlinear channel flow   总被引：1，自引：0，他引：1  

Jonas Nycander  Andrew McC. Hogg  Leela M. Frankcombe   《Ocean Modelling》2008,24(3-4):108-121

Open boundary conditions are derived for the one-dimensional nonrotating two-layer shallow-water equations. The conditions are based on characteristics of the external and internal modes. It is possible to find exact nonlinear characteristic conditions for the external mode, as well as approximate nonlinear conditions for the internal mode. These conditions can also be linearised by Taylor expansion; the approximate linear conditions are similar to those used in several previous studies. Both of the nonlinear and linearised conditions perform well, indicating that either the nonlinear or linearised conditions may potentially be extended to the more general case of multi-layer flows.  相似文献   

Modification and testing of a one‐dimensional energy and mass balance model for supraglacial snowpacks     

Andrew M. Fox  Ian C. Willis  Neil S. Arnold 《水文研究》2008,22(16):3194-3209

A one‐dimensional energy and mass balance snow model (SNTHERM) has been modified for use with supraglacial snowpacks and applied to a point on Haut Glacier d'Arolla, Switzerland. It has been adapted to incorporate the underlying glacier ice and a site‐specific, empirically derived albedo routine. Model performance was tested against continuous measurements of snow depth and meltwater outflow from the base of the snowpack, and intermittent measurements of surface albedo and snowpack density profiles collected during the 1993 and 2000 melt seasons. Snow and ice ablation was simulated accurately. The timing of the daily pattern of meltwater outflow was well reproduced, although magnitudes were generally underestimated, possibly indicating preferential flow into the snowpack lysimeter. The model was used to assess the quantity of meltwater stored temporally within the unsaturated snowpack and meltwater percolation rates, which were found to be in agreement with dye tracer experiments undertaken on this glacier. As with other energy balance studies on alpine valley glaciers, the energy available for melt was dominated by net radiation (64%), with a sizable contribution from sensible heat flux (36%) and with a negligible latent heat flux overall, although there was more complex temporal variation on diurnal timescales. A basic sensitivity analysis indicated that melt rates were most sensitive to radiation, air temperature and snowpack density, indicating the need to accurately extrapolate/interpolate these variables when developing a spatially distributed framework for this model. Copyright © 2008 John Wiley & Sons, Ltd.  相似文献   

泉水信息在研究水文地质条件中的应用     

杨现国 《河南国土资源》2000,(2)

根据仁村东泉、西泉流量变化特征与降水之间的有关信息 ,分析了泉域相应的水文地质条件 ,其与实际情况相吻合。用这种方法分析泉域水文地质条件 ,不仅可以加深对泉域水文地质条件的认识 ,而且对查明泉域水文地质条件 ,并合理投入工程量有着一定的指导意义。  相似文献   

测量平差中求解协因数的简化算法   总被引：3，自引：1，他引：2  

杨雪峰  龚涛  汪精河 《测绘科学》2009,34(1)

本文从测量平差精度评定的求解协因数阵的过程中,寻找了一种有关协因数阵的简便算法,此算法的特点在于从已知的解法中,提炼出一种便于理解和记忆的方法,从经典的平差解答中找出规律,从而避免了去死记硬背复杂的结论。本文针对提出的简便算法,在条件平差、间接平差、附参数的条件平差和附限制条件的间接平差中通过验证,结果是正确的。  相似文献