地磁测量中日变观测的常见问题     

高建尽  武同元 《北京测绘》2014,(6):106-108

地磁日变观测质量主要与仪器性能和观测点的环境有关。本文重点研究了目前在地磁日变测量中主要采用的HC90D氦光泵磁力仪的信号失锁问题,日变站的选址二个对于最终观测精度影响很大的问题,并提出了具体的解决方法。  相似文献   

基于CA模型的佛山市建设用地动态变化研究     

毛华锐  杨武年  桑学佳 《测绘软科学研究》2014,(5):19-23

元胞自动机具有能模拟复杂动态系统的强大能力,本文采用了多约束条件的元胞自动机模型,以广东佛山市2000年、2006年和2012年建设用地的变化为例,从自然、社会经济发展等方面综合考虑选取了高程、坡度、人口密度、道路交通、水系等对城市建设用地发展变化起决定作用的诸多因子,利用马尔科夫概率矩阵计算2000年～2006年建设用地变化,推算建设用地转移总量。结合Logistic-CA模型和决策树-CA模型,预测模拟了2012年的建设用地分布并与实际相比较,分析其整体精度和误差来源。结果显示基于CA模型的建设用地动态发展模拟具有良好的效果,可以为城市的发展规划,过程演变提供虚拟的实验手段和科学依据。  相似文献   

多时相遥感影像的变化监测方法研究     

罗方权  马克委  吴建良 《现代测绘》2014,(6):44-46

多时相遥感影像图变化监测已经在国民经济及国防建设领域得到了广泛应用。通过分析同一地域不同时相的遥感图像变化监测提供地物发生变化的信息,对资源环境数据进行更新及利用。论文围绕变化监测中的一些关键理论方法进行了研究。  相似文献   

美国内政部四轮战略规划的发展趋势及特点分析     

刘丽  陈丽萍  王威 《国土资源情报》2014,(9):6-13

美国内政部的战略规划是该部施政纲领的集中体现。四轮战略规划的目标从2003年强调资源保护、利用与休闲娱乐的平衡,到2007年增加全球经济、环境、政治和其他因素对内政部战略规划的影响,直至2014年强调资源的娱乐、人文观赏价值,并重视培养下一代的管理责任。内政部战略定位逐渐清晰。资源保护、经济发展、休闲娱乐的相对关系发生变化,从强调三者平衡到强调资源的休闲、文化等景观价值。  相似文献   

Google Earth和天地图在林地变更中的应用比较和优化          下载免费PDF全文

曲宏辉  张舒洁  王正茂  孙中元  刘成杰 《山东国土资源》2020,36(4):74-78

在森林资源监测过程中,特别是涉及林地变更工作时,遥感影像发挥了重要的作用。在实际工作中,上级部门下发的标准影像存在部分地区影像分辨率不高的问题,影响了林地变更工作的正常进行。为了拓展影像资源,使林地变更工作顺利进行,该文对Google Earth和天地图影像及校正配准后的精度进行比较研究,结果表明,配准前的Google Earth影像精度明显优于天地图影像;面积在1万hm^2及其以下的乡镇配准后的影像精度较高。  相似文献   

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陈连旺  詹自敏 《大地测量与地球动力学》2011,31(6):1-5

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Debating clean energy: Frames,counter frames,and audiences     

Michaël Aklin  Johannes Urpelainen 《Global Environmental Change》2013,23(5):1225-1232

In the United States, both scholars and practitioners have repeatedly emphasized the importance of “issue framing” for garnering public support for climate change policy. However, the debate frequently overlooks the importance of counter frames. For every framing attempt by advocates of climate policy, there will be a counter frame by the opponents of climate policy. How do counter frames influence the effectiveness of issue framing as a communication strategy? To answer this question, we report results from a survey experiment on a nationally representative sample of 1000 Americans on clean energy policy, a key policy issue in the public debate on climate change in the United States. Overall, we find that different combinations of positive and negative frames have remarkably little effect on support for clean energy policy. A follow-up on-line survey experiment with a convenience sample of 2000 Americans suggests that the counter frames are responsible for undermining the effects of the original frames.  相似文献   

Assessment of future runoff trends under multiple climate change scenarios in the Willamette River Basin,Oregon, USA     

Il‐Won Jung  Heejun Chang 《水文研究》2011,25(2):258-277

We investigated trends in future seasonal runoff components in the Willamette River Basin (WRB) of Oregon for the twenty‐first century. Statistically downscaled climate projections by Climate Impacts Group (CIG), eight different global climate model (GCM) simulations with two different greenhouse gas (GHG) emission scenarios, (A1B and B1), were used as inputs for the US Geological Survey's Precipitation Runoff Modelling System. Ensemble mean results show negative trends in spring (March, April and May) and summer (June, July and August) runoff and positive trends in fall (September, October and November) and winter (December, January and February) runoff for 2000–2099. This is a result of temperature controls on the snowpack and declining summer and increasing winter precipitation. With temperature increases throughout the basin, snow water equivalent (SWE) is projected to decline consistently for all seasons. The decreases in the centre of timing and 7‐day low flows and increases in the top 5% flow are caused by the earlier snowmelt in spring, decreases in summer runoff and increases in fall and winter runoff, respectively. Winter runoff changes are more pronounced in higher elevations than in low elevations in winter. Seasonal runoff trends are associated with the complex interactions of climatic and topographic variables. While SWE is the most important explanatory variable for spring and winter runoff trends, precipitation has the strongest influence on fall runoff. Spatial error regression models that incorporate spatial dependence better explain the variations of runoff trends than ordinary least‐squares (OLS) multiple regression models. Our results show that long‐term trends of water balance components in the WRB could be highly affected by anthropogenic climate change, but the direction and magnitude of such changes are highly dependent on the interactions between climate change and land surface hydrology. This suggests a need for spatially explicit adaptive water resource management within the WRB under climate change. Copyright © 2010 John Wiley & Sons, Ltd.  相似文献   

A broad‐scale assessment of the effect of improved soil management on catchment baseflow index     

I. P. Holman  T. M. Hess  S. C. Rose 《水文研究》2011,25(16):2563-2572

Although the importance of sustainable soil management is recognized, there are many threats to soils including widespread soil structural degradation. This reduces infiltration through the soil surface and/or the percolation of water through the soil profile, with important consequences for crop yields, nutrient cycling and the hydrological response of catchments. This article describes a broad‐scale modelling approach to assess the potential effect that improved agricultural soil management, through reduced soil structural degradation, may have on the baseflow index (BFI) of catchments across England and Wales. A daily soil–water balance model was used to simulate the indicative BFI of 45 696 thirty‐year model runs for different combinations of soil type, soil/field condition, land cover class and climate which encapsulate the variability across England and Wales. The indicative BFI of catchments was then calculated by upscaling the results by spatial weighting. WaSim model outputs of indicative BFI were within the 95% confidence intervals of the national‐average BFI values given for the Hydrology of Soil Type (HOST ? ) classes for 26 of the 28 classes. At the catchment scale, the concordance correlation coefficient between the BFI from the WaSim model outputs and those derived from HOST was 0·83. Plausible improvements in agricultural soil/field condition produced modest simulated increases of up to 10% in the indicative BFI in most catchments across England and Wales, although for much of southern and northern England the increases were less than 5%. The results suggest that improved soil management might partially mitigate the expected adverse effects of climate change on baseflow to rivers. Healthy, well‐functioning soils produce many additional benefits such as better agricultural yields and reduced pollutant movement, so improved soil management should provide win‐win opportunities for society, agricultural systems and the environment and provide resilience to some of the expected environmental impacts of climate change. Copyright © 2011 John Wiley & Sons, Ltd.  相似文献   

Shift trend and step changes for runoff time series in the Shiyang River basin,northwest China     

Z. L. Li  Z. X. Xu  J. Y. Li  Z. J. Li 《水文研究》2008,22(23):4639-4646

Shift trend and step changes were detected for runoff time series in the Shiyang River basin, one of the inland river basins in north‐west China. Annual runoff data from eight tributaries as well as both annual and monthly runoff from the mainstream from 1958 to 2003 were used. Seven statistical test methods were employed to identify the shift trends and step changes in the study. Mann–Kendall test, Spearman's Rho test, linear regression and Hurst exponent were used to detect past and future shift trends for runoff time series, while the distributed‐free CUSUM test, cumulative deviations and the Worsley likelihood ratio test were used to detect step changes for the same time series. Results showed that the annual runoff from Zamu, Huangyang and Gulang rivers, as well as both annual and monthly runoff from the mainstream, show statistically significant decreasing trends. Future tendency of runoff for both tributaries and mainstream were consistent with that from 1958 to 2003. Step changes probably occurred in 1961 for the runoff from Huangyang, Gulang and Dajing rivers according to the Worsley likelihood ratio test, but no similar results were found using the other two test methods. Three change points (1979, 1974 and 1973) were detected for the mainstream using different methods. These change points were close to the years that reservoirs started to be operated. Both climate change and human activities, especially the latter, contributed to the decreasing runoff in the study area. Between 21% and 79% of the reduction in runoff from the mainstream was due to the impact of human activities during the past few decades. Copyright © 2008 John Wiley & Sons, Ltd.  相似文献