基于非线性运动分析的CGCS2000下我国CORS站运动特征

CGCS2000(中国地心坐标系统2000)下CORS(全球导航卫星系统连续运行参考站)站的非线性运动主要受到地壳非构造形变信息、框架点公共误差信息和观测误差信息的组合影响,分析我国CORS站坐标时间序列中包含的非线性运动信息是维护CGCS2000坐标框架精确性、可靠性的基础.本文研究方法首先采用国际卫星对地观测数据及相关地球物理模型,计算了由质量负荷效应造成的地壳非构造形变, 并以此修正了这些非构造形变对国家CORS站坐标时间序列的影响.其次采用主成分空间滤波算法(PCA)提取质量负荷改正后的CGCS2000坐标框架公共误差(Common Mode Errors, CME)的时空特性.最后采用最大似然法定量估计了负荷改正和滤波后的国家CORS网坐标时间序列的噪声特性,采用加权最小二乘法评定了考虑不同噪声影响的CGCS2000框架下的国家CORS网年速度估值和实际精度.     

XAS80到CGCS2000坐标转换的自适应拟合推估算法

借鉴自适应滤波思想,将相似变换作为坐标变换函数模型的趋势项,把模型变换后的残差看成随机场,通过自适应因子调整信号向量与观测向量的先验权比,尝试通过自适应拟合推估法进行坐标变换,并将其应用于1980西安坐标系(XAS80)到2000国家大地坐标系(CGCS2000)的坐标变换。计算结果表明,自适应拟合推估法的坐标变换结果精度明显优于相似变换结果和拟合推估变换结果。     

建立全国CORS更新国家地心动态参考框架的几点思考

在介绍欧美国家和洲际连续运行参考站网(CORS)建设的基础上,分析了国外技术的发展趋势及其启示,阐述了国家CORS和全国联合CORS两个概念,建议由国家和全国联合CORS在满足一定条件下融合成国家级CORS,制定相关标准进行运营管理。国家CORS连同国家级CORS的首要目标是升级、更新和维持2000国家大地坐标系统(CGCS2000),即实现由国家CORS网为主维持的CGCS2000,以此为基础提出了采用CORS对CGCS2000进行更新的目标和方案。针对局部参考框架的建立,提出了框架网和基准网两个概念,分别用于建立区域地心动态参考框架以及国家坐标系与地方测图坐标系的连接,并给出了一个区域动态参考框架的建立方式。     

利用局域欧拉矢量法建立CGCS2000速度场模型

现有研究中,中国大陆速度场模型容易出现数据量小、连续性不佳、现势性不强等问题。基于近7年的中国地壳运动观测网络工程连续运行基准站GNSS(global navigation satellite system)观测数据,解算得到高精度陆态网基准站点的点位坐标和速度场,并利用提出的局部无缝Delaunay三角网反距离加权模型构建中国大陆格网速度场。相较现有的NNR-NUVEL1A(no net rotation Nubia velocity 1A)欧拉矢量模型与常用的速度场数值拟合模型,局部无缝Delaunay三角网反距离加权模型的精度最高,其水平速度场拟合精度优于1.5 mm/a; 采用陆态网约1 800个区域站进行外部检核,结果表明,东、北方向速度差值的绝对值平均值分别为1.11 mm/a、0.90 mm/a,中误差分别为1.50 mm/a、1.35 mm/a。相较于整体三角网而言,局域三角网在大陆边缘地区的拟合精度更优,水平速度场的插值精度更高,平均可以提高约0.3 mm/a,且不易产生粗差。局部无缝Delaunay三角网反距离加权模型不仅考虑了邻近点的距离和方位信息,还可以刻画出更为精细的局部特征,同时克服了边缘地区整体三角网跨度过大以及二级块体边缘处三角网不连续的缺点。     

西宁市CORS中坐标转换方法的研究

讨论了西宁市CORS中的坐标转换方法,研究了坐标转换方法,实现了三维空间基准到二维平面基准的高精度转换。     

Classification of vegetation in an open landscape using full-waveform airborne laser scanner data

Airborne laser scanning (ALS) is increasingly being used for the mapping of vegetation, although the focus so far has been on woody vegetation, and ALS data have only rarely been used for the classification of grassland vegetation. In this study, we classified the vegetation of an open alkali landscape, characterized by two Natura 2000 habitat types: Pannonic salt steppes and salt marshes and Pannonic loess steppic grasslands. We generated 18 variables from an ALS dataset collected in the growing (leaf-on) season. Elevation is a key factor determining the patterns of vegetation types in the landscape, and hence 3 additional variables were based on a digital terrain model (DTM) generated from an ALS dataset collected in the dormant (leaf-off) season. We classified the vegetation into 24 classes based on these 21 variables, at a pixel size of 1 m. Two groups of variables with and without the DTM-based variables were used in a Random Forest classifier, to estimate the influence of elevation, on the accuracy of the classification. The resulting classes at Level 4, based on associations, were aggregated at three levels — Level 3 (11 classes), Level 2 (8 classes) and Level 1 (5 classes) — based on species pool, site conditions and structure, and the accuracies were assessed. The classes were also aggregated based on Natura 2000 habitat types to assess the accuracy of the classification, and its usefulness for the monitoring of habitat quality. The vegetation could be classified into dry grasslands, wetlands, weeds, woody species and man-made features, at Level 1, with an accuracy of 0.79 (Cohen’s kappa coefficient, κ). The accuracies at Levels 2–4 and the classification based on the Natura 2000 habitat types were κ: 0.76, 0.61, 0.51 and 0.69, respectively. Levels 1 and 2 provide suitable information for nature conservationists and land managers, while Levels 3 and 4 are especially useful for ecologists, geologists and soil scientists as they provide high resolution data on species distribution, vegetation patterns, soil properties and on their correlations. Including the DTM-based variables increased the accuracy (κ) from 0.73 to 0.79 for Level 1. These findings show that the structural and spectral attributes of ALS echoes can be used for the classification of open landscapes, especially those where vegetation is influenced by elevation, such as coastal salt marshes, sand dunes, karst or alluvial areas; in these cases, ALS has a distinct advantage over other remotely sensed data.     

手持式GPS仪改正参数的内业确定方法

讨论了手持式GPS仪改正参数的内业确定方法 ,并给出了利用Excel表格进行计算的具体解决方案。与传统方法相比,本方法具有完全室内作业、省时省力、参数可靠性高的特点。     

平面控制网的整合与2000国家大地坐标系的转换

2000国家大地坐标系(CGCS 2000)的启用,对原有的测绘成果将产生直接影响。为确保常用测量坐标系与CGCS 2000的衔接和转换,需要有效地整合原有的测绘基础数据,探究地方测量坐标系与CGCS 2000之间的转换方法,确定地方坐标系与CGCS 2000之间的联系。本文分析了石家庄市原有的基础测绘数据分析,提出了平面控制网整合方案和坐标整体转换方法。     

GPS RTK positioning via Internet-based 3G CDMA2000/1X wireless technology

The latest evolution in digital wireless technology, third-generation (3G) Code Division Multiple Access/Single Carrier (CDMA2000/1X) wireless network, is applicable for transmitting real-time kinematic (RTK) GPS correction messages. Fast and reliable, publicly available wireless networks, combined with highly accessible Internet connectivity, allows the multicasting of messages to mobile users, who are no longer restricted to traditional private UHF wireless networks. Nationwide public wireless network systems continue to expand and can provide an inexpensive infrastructure for the emerging multi-reference network system. Transmission performance via the Internet-based CDMA2000/1X outperforms UHF technology in transmission throughput and latency, as well as in the RTK initialization time and positional accuracy.     

Seismic soil pressure for building walls: An updated approach

The Mononobe–Okabe (M–O) method developed in the 1920s in Japan continues to be widely used despite many criticisms and its limitations. The method was developed for gravity walls retaining cohesionless backfill materials. In design applications, however, the M–O method, or any of its derivatives, is commonly used for below ground building walls. In this regard, the M–O method is one of the most abused methods in the geotechnical practice. Recognizing the limitation of the M–O method, a simplified method was recently developed to predict lateral seismic soil pressure for building walls. The method is focused on the building walls rather than retaining walls and specifically considers the dynamic soil properties and frequency content of the design motion in its formulation.