横断山区地表真实面积与垂直投影面积差异分析 ——以雅江县为例

横断山脉地形起伏复杂,以垂直投影面积作为地表真实面积进行定量计算会产生较大误差.本文以横断山脉中部雅江县为例,基于DEM数据和地表覆盖产品数据集,利用地表粗糙度的地学意义,计算了雅江县不同土地利用类型地表真实面积,并分析了地表真实面积与垂直投影面积之间的差异.结果表明:雅江县地表面积与投影面积的差异与DEM分辨率呈正相...     

On the reliability of the VCV Matrix: A case study based on GAMIT and Bernese GPS Software

Commonly, the variance-covariance (VCV) matrix derived from GPS processing software underestimates the magnitude of the error, mainly due to the fact that physical correlations are normally neglected. The GAMIT and Bernese software packages serve the scientific community as important tools for GPS measurement processing and analyzing, especially in precise applications. Therefore, the reliability of the VCV matrices derived by the GAMIT and Bernese packages is of great importance. Formal accuracies derived from both software need to be scaled by applying a scaling factor (SF) that multiplies the software-derived formal errors. However, to the best of our knowledge, no standard approach approved by the GPS community exists. In this report, an analysis is carried out in order to test the reliability and the validity of the VCV matrices in both software, and to provide SFs needed to calculate the realistic accuracies reflecting the actual error levels. The method applied in this study allows deriving SFs for formal accuracies obtained from GAMIT and Bernese. The results attained from the time series of eight days for eight baselines (lengths of 20–415 km) indicate that the overall SF for GAMIT is more than 10 times smaller than for Bernese (1.9 and 23.0, respectively). Although no distance-dependent SF was detected in either case, the session-duration dependence was detected for the Bernese software, while no clear session-duration dependence was observed for the GAMIT. Furthermore, no receiver/antenna dependence could be deduced from the results of this analysis.     

基于典型物候特征的MODIS-EVI时间序列数据 农作物种植面积提取方法 —小区域冬小麦实验研究

利用MODIS植被指数时间序列这一特性,以北京市通州及周边为实验区,冬小麦种植面积为研究对象,提出 了农作物种植面积指数模型(Pan-CPI模型)的概念,并构造了冬小麦特征物候期植被指数与种植面积的定量函数关系, 通过样区TM影像求解关键参数,对研究区冬小麦种植面积测量方法进行了试验研究。研究结果表明：(1)Pan-CPI模 型能够很好地反映特定目标农作物种植面积状况,为基于植被指数时间序列影像识别农作物种植面积提供了新方法; (2)精度分析结果表明：Pan-CPI模型具有很高的稳定性,且不受样本变化的影响,只要达到满足模型计算的样本量(如： 5%),多次测量结果间具有很好的一致性。选取MODIS 6×6像元大小的窗口时,TM样本的复相关系数(R2)稳定在0.85 左右,与TM结果比较,窗口相对精度稳定在95%左右,区域精度稳定在92%以上,经调整的区域精度高达96%以上; (3)对于种植结构复杂、目标作物种植破碎的地区,Pan-CPI模型可以充分利用MODIS植被指数时间序列的优势,有效改 善TM单时相和多时相提取信息因时相缺失无法表征作物变化的不足。     

浙西低山丘陵区景观格局变化的高程分异研究——以桐庐县为例

国内外学者对于景观格局的地形分异研究,经历了从景观类型分布高程差异到景观指数高程分异研究的过程,目前处在景观格局静态地形分异阶段。本文利用浙江西部桐庐县1996、2004的土地利用现状图和DEM数据,对其1996-2004年景观格局动态演变特征的高程分异规律进行研究。研究对桐庐县1996、2004年的土地利用现状图进行处理获得景观类型分布图,通过1∶10000的DEM数据的分带操作,生成不同高程带的景观类型分布图。选取斑块密度、景观形状指数、分维数、破碎度、香农多样性指数、香农均匀度指数等景观格局指数,并在ArcGIS和Fragstats的支持下,计算出各带两个年份的景观格局指数并作对比分析。结果表明:研究区景观格局演变具有明显的高程分异特征,不仅表现为景观类型分布的变化与高程变化相关,而且体现在景观格局指数的变化值随高程上升而增减的趋势也有一定的规律性:景观水平上所有指数变化的剧烈程度大致与高程呈负相关关系,景观类型水平上各景观类型的破碎度、和斑块密度变化程度随海拔升高趋于缓和。     

应用遥感时序数据研究植被变化与气候因子的关系——以环渤海地区为例

在全球气候变化背景下研究陆地植被的时空变化规律,探讨气候因素的驱动作用,对于预测未来气候变化对生态系统的可能影响、制定合适的生态环境保护策略具有重要意义。利用2000—2009年MODIS归一化差值植被指数(normalized difference vegetation index,NDVI)时间序列数据和地面气象站点的气温、降水量数据,从遥感角度分析环渤海地区植被的时空变化,并研究变化与气温、降水的相关关系,探讨区域植被年内和年际变化的驱动因素。结果表明,2000—2009年环渤海地区植被覆盖总体呈增加的趋势,但存在一定的空间异质性,局部有减少的倾向;区域植被的生长受温度和降水的双重驱动,对降水和温度的响应存在明显的滞后,滞后期大约为1个合成期;年际的变化主要受降水和人类活动的影响,降水增加可使区域NDVI提高;不同的人类活动会导致NDVI向相反的方向发展。     

基于分形的数字水系集水面积阈值确定研究

集水面积阈值的确定是基于数字高程模型提取水系过程中的关键环节,但目前集水面积阈值的确定存在着随意性和主观性.本文引入分维数量化集水面积阈值对水系提取的影响.研究表明,在给定标度区间内集水面积阈值和分维数存在着良好的回归关系.二者的拟合方程可用来进行集水面积阈值的合理确定和水系的准确提取.     

遥感影像与POI数据相结合的城市建成区提取适用性研究——以沈阳市为例

城市建成区的发展状况是地理国情监测的重要内容,本文基于遥感影像数据和POI数据对城市建成区进行提取,针对二者的适用性问题进行了研究。试验以沈阳市为研究区域,在研究区域内选择2016年遥感影像数据和POI数据作为数据源进行对比分析。首先,对遥感影像数据和POI数据进行预处理;其次,通过监督分类的方法对遥感影像进行建成区的提取;然后,采用核密度估计法分析POI数据并提取出建成区;最后,利用叠加分析法对比分析这两种数据的适用性。试验结果表明：使用遥感影像数据作为数据源可以较为全面客观地反映城市建成区的发展现状;利用POI数据提取出的城市建成区具有较强的经济属性,能够很好地反映出城市中的经济活跃区。     

Local geoid determination combining gravity disturbances and GPS/levelling: a case study in the Lake Nasser area, Aswan, Egypt

 The use of GPS for height control in an area with existing levelling data requires the determination of a local geoid and the bias between the local levelling datum and the one implicitly defined when computing the local geoid. If only scarse gravity data are available, the heights of new data may be collected rapidly by determining the ellipsoidal height by GPS and not using orthometric heights. Hence the geoid determination has to be based on gravity disturbances contingently combined with gravity anomalies. Furthermore, existing GPS/levelling data may also be used in the geoid determination if a suitable general gravity field modelling method (such as least-squares collocation, LSC) is applied. A comparison has been made in the Aswan Dam area between geoids determined using fast Fourier transform (FFT) with gravity disturbances exclusively and LSC using only the gravity disturbances and the disturbances combined with GPS/levelling data. The EGM96 spherical harmonic model was in all cases used in a remove–restore mode. A total of 198 gravity disturbances spaced approximately 3 km apart were used, as well as 35 GPS/levelling points in the vicinity and on the Aswan Dam. No data on the Nasser Lake were available. This gave difficulties when using FFT, which requires the use of gridded data. When using exclusively the gravity disturbances, the agreement between the GPS/levelling data were 0.71 ± 0.17 m for FFT and 0.63 ± 0.15 for LSC. When combining gravity disturbances and GPS/levelling, the LSC error estimate was ±0.10 m. In the latter case two bias parameters had to be introduced to account for a possible levelling datum difference between the levelling on the dam and that on the adjacent roads. Received: 14 August 2000 / Accepted: 28 February 2001     

Intercomparison and validation of MODIS and GLASS leaf area index (LAI) products over mountain areas: A case study in southwestern China

The validation study of leaf area index (LAI) products over rugged surfaces not only gives additional insights into data quality of LAI products, but deepens understanding of uncertainties regarding land surface process models depended on LAI data over complex terrain. This study evaluated the performance of MODIS and GLASS LAI products using the intercomparison and direct validation methods over southwestern China. The spatio-temporal consistencies, such as the spatial distributions of LAI products and their statistical relationship as a function of topographic indices, time, and vegetation types, respectively, were investigated through intercomparison between MODIS and GLASS products during the period 2011–2013. The accuracies and change ranges of these two products were evaluated against available LAI reference maps over 10 sampling regions which standed for typical vegetation types and topographic gradients in southwestern China.The results show that GLASS LAI exhibits higher percentage of good quality data (i.e. successful retrievals) and smoother temporal profiles than MODIS LAI. The percentage of successful retrievals for MODIS and GLASS is vulnerable to topographic indices, especially to relief amplitude. Besides, the two products do not capture seasonal dynamics of crop, especially in spring over heterogeneously hilly regions. The yearly mean LAI differences between MODIS and GLASS are within ±0.5 for 64.70% of the total retrieval pixels over southwestern China. The spatial distribution of mean differences and temporal profiles of these two products are inclined to be dominated by vegetation types other than topographic indices. The spatial and temporal consistency of these two products is good over most area of grasses/cereal crops; however, it is poor for evergreen broadleaf forest. MODIS presents more reliable change range of LAI than GLASS through comparison with fine resolution reference maps over most of sampling regions. The accuracies of direct validation are obtained for GLASS LAI (r = 0.35, RMSE = 1.72, mean bias = −0.71) and MODIS LAI (r = 0.49, RMSE = 1.75, mean bias = −0.67). GLASS performs similarly to MODIS, but may be marginally inferior to MODIS based on our direct validation results. The validation experience demonstrates the necessity and importance of topographic consideration for LAI estimation over mountain areas. Considerable attention will be paid to the improvements of surface reflectance, retrieval algorithm and land cover types so as to enhance the quality of LAI products in topographically complex terrain.     

复杂地形条件的地表面积计算软件开发

针对现有地表面积计算软件在计算复杂地形时操作异常繁琐,且所生成三角网为单边界三角网这一问题,开发了一种新的地表面积计算软件。采用C#语言,利用数字地图,按照三角网建立地面模式,通过三角网内高程内插、点坐标集判断和分类等方式,完成待测区域内地表的并行分块与三角网的重建,实现复杂地形条件下的多边界三角网的生成和地表面积的一体化计算,并将区域内各个三角形的编号和面积直接显示于计算机屏幕上。实验结果表明:该软件使用直观方便,操作简单,精度可靠,适用范围广,可以有效地减少计算复杂地形地表面积时的操作步骤,降低工作强度,并能输出面积计算结果的各种信息。     

关于多功能房屋共有建筑面积分摊计算模型的探讨

房产测绘中共有建筑面积的分摊是最基本、最重要也是最为复杂的问题,本文针对复杂多功能房屋共有建筑面积分摊,依据GB/T17986.1-2000《房产测量规范》,通过分析房屋的功能结构和共有建筑面积的分摊级别,提出了共有面积分摊计算的方法及其数学模型,并列举了一个多级分摊的例子进行了详细阐述。     

房产面积测量的系统性研究

房产面积测量具有不确定性。究其原因是专业人员对房产面积的认识有差异,对物业功能属性认识模糊,同时还缺少科学的评判方法。本文突破房产面积的平面概念,对房产面积进行了空间系统性分析,提出容积率条件下的建筑面积是最基本的房屋产权面积,从而剥离出没有土地使用权的建筑面积。通过建立决策规则,对构成物业功能空间各要素在不同组合条件下的具体物业空间作出是否计算建筑面积的评判。本研究已用于指导GB《房产测绘规范》江西省地方细则编制的实践。     

Predictive fire occurrence modelling to improve burned area estimation at a regional scale: A case study in East Caprivi,Namibia

Fires threaten human lives, property and natural resources in Southern African savannas. Due to warming climate, fire occurrence may increase and fires become more intense. It is crucial, therefore, to understand the complexity of spatiotemporal and probabilistic characteristics of fires. This study scrutinizes spatiotemporal characteristics of fires and the role played by abiotic, biotic and anthropogenic factors for fire probability modelling in a semiarid Southern African savanna environment. The MODIS fire products: fire hot spots (MOD14A2 and MYD14A2) and burned area product MODIS (MCD45A1), and GIS derived data were used in analysis. Fire hot spots occurrence was first analysed, and spatial autocorrelation for fires investigated, using Moran's I correlograms. Fire probability models were created using generalized linear models (GLMs). Separate models were produced for abiotic, biotic, anthropogenic and combined factors and an autocovariate variable was tested for model improvement. The hierarchical partitioning method was used to determine independent effects of explanatory variables. The discriminating ability of models was evaluated using area under the curve (AUC) from the receiver operating characteristic (ROC) plot. The results showed that 19.2–24.4% of East Caprivi burned when detected using MODIS hot spots fire data and these fires were strongly spatially autocorrelated. Therefore, the autocovariate variable significantly improved fire probability models when added to them. For autologistic models, i.e. models accounting for spatial autocorrelation, discrimination was good to excellent (AUC 0.858–0.942). For models not counting spatial autocorrelation, prediction success was poor to moderate (AUC 0.542–0.745). The results of this study clearly showed that spatial autocorrelation has to be taken in to account in the fire probability model building process when using remotely sensed and GIS derived data. This study also showed that fire probability models accounting for spatial autocorrelation proved to be superior in regional scale burned area estimation when compared with MODIS burned area product (MCD45A1).     

基于3S技术的采煤沉陷区土地利用变化分析——以淮北闸河矿区为例

以淮北闸河矿区为例,以煤炭资源开发引起的土地资源与环境的演变为研究对象,采用3S技术获取该区主要土地利用类型信息,建立土地利用变化转移矩阵,并对该区的土地利用变化及驱动力因素进行初步分析。研究表明,因矿区内煤炭开采和经济的持续发展,使得矿区土地遭受不同程度的毁损。通过采取合理的城乡规划和土地环境整治工程,矿区的土地仍然得到高效利用。     

三峡库区土地利用格局变化的分形结构研究——以开县为例

运用分形理论建立了研究区土地利用/覆被镶嵌体的分形结构模型,对各种景观的分维值进行了计算,讨论了各种景观形态的复杂性和稳定性及三峡工程实施十年间其稳定性和复杂性的动态变化。结果表明:分维值是研究区域土地利用/覆被镶嵌体景观格局的一种综合性定量指标,通过对土地利用景观类型的分维值进行分析,可以获取其形态的复杂性、稳定性信息。1992年和2002年两个时期研究区土地利用景观类型斑块形态复杂性和稳定性由大到小的顺序均依次为:未利用地、草地、建设用地、灌木林、森林、水田、旱地。十年间研究区旱地、建设用地和未利用地斑块形态变得愈加不规则,草地、灌木林、森林和水田的斑块形状变得愈加规则;十年间研究区旱地、建设用地和未利用地的形态稳定性变弱,草地、森林、灌木林和水田的形态稳定性增强。     

Minimum conformal mapping distortion according to Chebyshev’s principle: a case study over peninsular Spain

Defining the distortion of a conformal map projection as the oscillation of the logarithm of its infinitesimal-scale σ, Chebyshev’s principle states that the best (minimum distortion) conformal map projection over a given region Ω of the ellipsoid is characterized by the property that σ is constant on the boundary of that region. Starting from a first map of Ω, we show how to compute the distortion δ₀(Ω) of this Chebyshev’s projection. We prove that this minimum possible conformal mapping distortion associated with Ω coincides with the absolute value of the minimum of the solution of a Dirichlet boundary-value problem for an elliptic partial differential equation in divergence form and with homogeneous boundary condition. If the first map is conformal, the partial differential equation becomes a Poisson equation for the Laplace operator. As an example, we compute the minimum conformal distortion associated with peninsular Spain. Using longitude and isometric latitude as coordinates, we solve the corresponding boundary-value problem with the finite element method, obtaining δ₀(Ω)=0.74869×10⁻³. We also quantify the distortions δ_l and δ_utm of the best conformal conic and UTM (zone 30) projections over peninsular Spain respectively. We get δ_l=2.30202×10⁻³ and δ_utm=3.33784×10⁻³.     

狭长区域下基于正交法的GPS高程拟合研究

将GPS点大地高直接转换成正常高,越来越广泛地应用于建立高程控制网的实践中。而要保证GPS点高程精度的关键是高程异常拟合模型选择的合理性。文中介绍了在狭长带状区域下利用正交函数法拟合GPS点高程的数学模型。并利用试验数据进行比对分析。结果表明,文中提出的方法计算具有算法稳定,成果合理的特点。     

Monitoring urban growth on the European side of the Istanbul metropolitan area: A case study

Istanbul is the largest city in Turkey with an area of around 5750 km² and a population of around 10.8 M (2000). In 1980, the population was only around 4.7 M and so has more than doubled in only 2 decades. In 2000, around 65% of the population were living on the European side of the city with its large industrial/commercial and trade centres. The population is increasing as a result of both births exceeding deaths and mass immigration. Consequently, planned and unplanned housing are increasing while green areas are decreasing in area. Monitoring urban growth will enable the Municipality of Istanbul to better manage this complex urban area.     

SPOT5城区影像几何精校正点位和面积精度研究

为深入研究二维多项式校正SPOT5城区影像(2.5m)的点位和面积精度,本文分别使用不同精度(GPS点和1∶10000地形图获取的点),不同数量(25和6)的地面控制点校正影像。并利用另外的10个GPS点作为检核点分别检核四种校正结果的点位和面积精度。     

青海地区三级GPS大地控制网的建立

针对青海地区地理环境的特点和大地控制网的现状,从GPS控制网设计与布测、数据处理、控制网质量检测和成果管理等方面对青海地区三级GPS大地控制网的建立进行了分析研究。在此基础上,总结了在高原困难地区建立GPS网的一些经验。