Modeling of spatial distributions of farmland density and its temporal change using geographically weighted regression model

This study used spatial autoregression（SAR） model and geographically weighted regression（GWR） model to model the spatial patterns of farmland density and its temporal change in Gucheng County,Hubei Province,China in 1999 and 2009,and discussed the difference between global and local spatial autocorrelations in terms of spatial heterogeneity and non-stationarity. Results showed that strong spatial positive correlations existed in the spatial distributions of farmland density,its temporal change and the driving factors,and the coefficients of spatial autocorrelations decreased as the spatial lag distance increased. SAR models revealed the global spatial relations between dependent and independent variables,while the GWR model showed the spatially varying fitting degree and local weighting coefficients of driving factors and farmland indices（i.e.,farmland density and temporal change）. The GWR model has smooth process when constructing the farmland spatial model. The coefficients of GWR model can show the accurate influence degrees of different driving factors on the farmland at different geographical locations. The performance indices of GWR model showed that GWR model produced more accurate simulation results than other models at different times,and the improvement precision of GWR model was obvious. The global and local farmland models used in this study showed different characteristics in the spatial distributions of farmland indices at different scales,which may provide the theoretical basis for farmland protection from the influence of different driving factors.     

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1961-2010年中国400mm和800mm等雨量线时空变化

以中国1961-2010年逐日降水数据为基础,利用等值线加权平均位置的方式对400 mm和800 mm等雨量线的空间位置进行定量化处理。采用Kendall 秩次相关检验法、Morlet小波分析法、滑动t-检验法和Yamamoto法时间序列分析方法,对全国50年来 400 mm和800 mm等雨量线的空间位移特征进行了系统揭示:1961-2010年期间,400 mm和800 mm等雨量线加权平均位置坐标分别为（106°07'12"E,39°25'13"N）和（110°16'31"E,34°12'04"N）。趋势性结果表明,全国400 mm和800 mm等雨量线有向西和向南发生移动的趋势,其中400 mm等雨量线向西移动明显,800 mm等雨量线向南移动明显;周期性结果表明,全国400 mm等雨量线在经向和纬向上发生迁移的主周期分别为9年和 12年,800 mm等雨量线在经向和纬向变化均存在7年的主周期;突变性结果表明,400 mm等雨量线空间位置的突变年为1995-1996年（纬度）,800 mm等雨量线空间位置的突变年为1975年、2002年（经度）和1980年、1982年和1987年（纬度）。     

中国美丽乡村空间格局演变及其影响因素

以2014年、2017年、2020年对应的140、560、1216个美丽乡村为研究对象,运用GIS空间分析方法研究美丽乡村空间格局演变特征,采用地理探测器和多尺度地理加权回归探究美丽乡村空间格局的影响因素及其在空间上的分异。研究表明：① 美丽乡村空间分布的集聚性增强,主要集聚区呈现“带状-网状-面状”分布的演变趋势,热点区由沿海地带向内扩散。② 美丽乡村的空间分异是多因素共同作用的结果,但各影响因素对美丽乡村空间分异的解释度呈显著差异,其中非物质文化遗产、5A级景区、人口密度对美丽乡村空间分布的解释力最大。③ 主要影响因素对美丽乡村空间分布的影响作用存在空间差异,且局部不平衡性显著,正相关和负相关分析单元具有呈块状与带状的聚集特征。     

FCM聚类算法协同Canny算子的遥感影像边缘检测方法

提出一种FCM聚类算法协同Canny算子的遥感影像边缘检测方法,算法采用中值滤波消除原始遥感影像中的非高斯噪声;采用FCM(Fuzzy C-mean)聚类算法将滤波处理后的遥感影像中的像素分为两类:边缘类像素和非边缘类像素,并得到聚类影像;最后采用Canny算子对聚类影像进行边缘检测得到遥感影像地物边缘信息。实验结果表明,文中提出的方法能有效消除遥感影像中的混合噪声并准确地检测出地物目标的边缘,是一种有效的遥感影像边缘检测方法。     

油气勘探开发数据体平均值代表性分析

油气勘探开发涉及各类数据体,同一数据体可得多种平均值,目前尚无明确而有效的方法以判断何种平均值能客观反映数据体的典型水平。运用数据统计平均分析方法,对勘探开发实践中的孔隙度、渗透率、产量、成本等数据体进行系统分析,确立了加权中位数计算公式和平衡中位数法则。加权中位数计算公式适于分析不同领域正常有序数据体的基本特征,加权中位数为正常有序数据体的平衡点;平衡中位数法则适于确定有足够大数据容量、能满足统计分析基本要求、能选择合理权衡指标的正常有序数据体的典型水平;有明确物理意义的加权平均值也可确定数据体的典型水平。     

BDS/GPS实时动态网络伪距差分定位

针对基于单基准站的伪距差分定位方法中,随着流动站与基准站距离的增加,大气误差相关性减弱,定位精度将会降低的问题,该文采用网络伪距差分方法,利用网络将多个基准站的伪距改正数实时传输给流动站,并内插流动站改正数,提高定位精度的同时扩大差分范围。实验表明,该方法提高了常规伪距定位精度,实现了实时分米级定位,可满足大多数用户的导航定位需求。     

北方地区日光温室气候适宜性区划方法

通过对我国北方地区影响日光温室生产的主要气候因素进行分析,从光、温、风、雪4个方面选取了冬季总辐射、日光温室生产季阴天日数、年极端最低气温、冬季平均气温、生产季月最大风速平均值、年最大积雪深度平均值6个因子作为气候适宜性区划指标,采用加权指数求和的评价方法建立综合气候适宜性区划指标模型,在利用层次分析法对区划指标进行量化分析确定其权重的基础上,借助GIS技术,得到北方地区日光温室发展的气候适宜性区划图。为了细化区划结果,将研究区域气候特征明显不同的典型区域分别进行进一步区划。结果表明:该方法不仅理论性较强,与实际相吻合的区划结果也说明该方法还具有良好的实用性。     

Estimation of pH optima and tolerances of diatoms in lake sediments by the methods of weighted averaging,least squares and maximum likelihood,and their use for the prediction of lake acidity

Ecological optima and tolerances with respect to autumn pH were estimated for 63 diatom taxa in 47 Finnish lakes. The methods used were weighted averaging (WA), least squares (LS) and maximum likelihood (ML), the two latter methods assuming the Gaussian response model.WA produces optimum estimates which are necessarily within the observed lake pH range, whereas there is no such restriction in ML and LS. When the most extreme estimates of ML and LS were excluded, a reasonably close agreement among the results of different estimation methods was observed. When the species with unrealistic optima were excluded, the tolerance estimates were also rather similar, although the ML estimates were systematically greater.The parameter estimates were used to predict the autumn pH of 34 other lakes by weighted averaging. The ML and LS estimates including the extreme optima produced inferior predictions. A good prediction was obtained, however, when prediction with these estimates was additionally scaled with inverse squared tolerances, or when the extreme values were removed (censored). Tolerance downweighting was perhaps more efficient, and when it was used, no additional improvement was gained by censoring. The WA estimates produced good predictions without any manipulations, but these predictions tended to be biased towards the centroid of the observed range of pH values.At best, the average bias in prediction, as measured by mean difference between predicted and observed pH, was 0.082 pH units and the standard deviation of the differences, measuring the average random prediction error, was 0.256 pH units.     

一种基于小波变换的InSAR干涉图滤波方法

提出一种基于小波变换的InSAR干涉图滤波算法,此算法先用小波变换对干涉图数据做多级分解,得到图像的多级近似部分系数和3个(水平、垂直、对角线)方向的细节部分系数,然后分别对每一级各个方向的细节部分系数检测其是否为对应方向的边缘,对边缘处的系数根据边缘的方向不同,用不同的方向模板平滑后,再中值滤波;对非边缘处的系数直接中值滤波。用真实的InSAR干涉图实验结果证明此方法具有较好的滤波效果。