CORS系统在航空重力测量地面GNSS基站解算中的应用

航空重力测量是以飞机为载体,快速、高效获取大面积中、高频地球重力场信息的航空物探测量方法。航空重力测量技术的商业化运行归功于动态差分GNSS定位技术的成熟,使得载体的动态定位、动态测速和加速度解算精度大大提高,而差分GNSS技术解算载体动态定位的精度又依赖于地面基准站坐标精度。在实际作业中,通过组建控制网并设立地面GNSS基站,联测国家GNSS控制点,不仅需要花费较多的经济成本和时间成本,而且在人迹罕至的沼泽、高原、荒漠无人区以及远离大陆的海岛礁地区,这种方法都面临很大的困难。随着我国CORS站建设的不断深入,CORS系统精度和网度不断提高,利用CORS站数据,通过GAMIT等软件进行地面GNSS基站解算来确定其准确坐标位置的方法成为一种新趋势。本文以某测区实际数据为例,对比分析了两种方法得到的基站坐标精度及对重力测量结果的影响,介绍了CORS系统在航空重力测量地面GNSS基站解算中的应用效果,说明利用CORS系统解算不仅满足航空重力测量精度要求,而且能够提高工作效率。     

北斗三频伪距相关随机模型单站建模方法

为了提供可靠的伪距随机模型,基于3个线性无关的北斗三频伪距/载波无几何无电离层(GIF)组合,研究了一种利用单站数据估计北斗三频伪距相关随机模型算法。该算法首先利用低阶多项式对GIF组合进行拟合,以尽可能消除非伪距噪声以外的其他常数和误差,然后利用多元线性回归分析实现对3个线性无关的GIF组合随机噪声同时建模,最后再由线性组合关系变换得到原始北斗三频伪距相关随机模型。经北斗三频实测数据验证结果表明,该算法可实现北斗非差三频伪距相关随机模型的单站解算,有利于为导航定位以及完好性监测提供精准随机模型。     

Identifying geospatial services across heterogeneous taxonomies

Geospatial services with different functions are assembled together to solve complex problems. Different taxonomies are developed to categorize these services into classes. As differences in granularity and semantics exist among these taxonomies, the identification of services across different taxonomies has become a challenge. In this paper, an approach to identify geospatial services across heterogeneous taxonomies is proposed. Using formal concept analysis, existing heterogeneous taxonomies are decomposed into semantic factors and their various combinations. With these semantic factors, a super taxonomy is established to integrate the original heterogeneous taxonomies. Finally, with the super taxonomy as a cross-referencing system, geospatial services with classes in original taxonomies are identifiable across taxonomies. Experiments in service registries and a social media-based spatial-temporal analysis project are presented to illustrate the effectiveness of this approach.     

中国大陆流域分区TRMM降水质量评价

根据中国境内2 257个气象站点1998-2013年逐日降水资料,结合流域分区,采用探测准确性、相关系数以及相对误差等指标,对热带降水测量（TRMM）降水精度和一致性进行系统评价。结果表明:① TRMM日降水准确性从东南沿海向西北内陆递减;② 气象站点年均降水日数显著大于TRMM年均降水日数;③ 西北片区以外气象站点降水量和TRMM降水量在月尺度和年尺度上均具有较好的相关关系;④ 各流域年均TRMM面降水量均高于气象站点面降水量,且TRMM面降水量相对误差雨季较小,枯季较大;⑤ 各流域TRMM面降水量与气象站点面降水量演变趋势基本一致,南方各流域年降水量均呈减少趋势,北方各流域年降水量均呈增加趋势,全国尺度上年降水量呈微弱的减少趋势。     

天津市滨海新区芦苇湿地恢复适宜性评价

利用综合评价模型,结合地理信息系统技术的空间分析功能,以土地利用、土壤类型、坡度、降雨量和人类干扰活动作为评价因子,对天津滨海新区芦苇湿地恢复进行了适宜性评价。结果表明,较适宜开展湿地恢复的比例为21.46%,一般适宜比例为21.87%,不适宜比例占56.68%,其中较适宜湿地恢复的区域集中分布在北大港湿地自然保护区周边、独流减河下游、北塘入海口以及沿海滩涂,海河流域两侧也有零星分布。在适宜性评价基础上,对未来芦苇湿地恢复与建设的重点区域进行了成效预评估,芦苇对TC、TN、TP的年吸收通量约为1.3935×104、0.0258×104、0.0017×104t,能有效地减少入海排污压力和污染物对近岸海域环境质量的影响。研究结论可为天津湿地治理与生态恢复、土地利用结构调整、景观优化等提供理论依据和科学参考。     

Zircon U-Pb Geochronology,Geochemistry and Petrogenesis of Early Cretaceous A-type Granites in the Mikengshan Area,Southern Jiangxi ProvinceEI北大核心CSCD

In the Mikengshan-Yanbei area, a special region for the tin mineralization in South China, there are some Yanshanian granites and porphyries and associated porphyry tin deposits (e.g., Yanbei). Although the tin mineralization is closely associated with the granitoids magmatism, the age and petrogenesis of the granites remain controversial. The Mikengshan pluton, which intrudes into the rhyolitic tuff and pyroclastic rocks of the Upper Jurassic Jilongzhang Formation, is the largest one in Mikengshan-Yanbei area and mainly consists of K-feldspar bearing granites. In this study, we report new age and geochemical data for the Mikengshan K-feldspar bearing granites. LA-ICP-MS zircon U-Pb age dating shows that they were generated in the Early Cretaceous (~138 Ma). They have high SiO2 (74.42% to 76.69%), low Al2O3 (12.39% to 13.49%) and Mg# (11 to 19), and negative Eu, Sr and Ba anomalies, and are rich in potassium (most K2O/Na2O=1.37 to 1.94) and high field strength elements (HFSEs), and are weakly peraluminous (A/CNK=1.03 to 1.1) with high 10000×Ga/Al ratios (3.46 to 4.96) and slightly high zircon saturation temperatures (807 ℃ to 817 ℃), showing the characteristics of the typical A-type granites. Moreover, they have high Rb contents 842×10-6 to 1295×10-6, Rb/Sr (90 to 255) ratios and show rare earth elements (REE) tetrad effect, which are similar to those of high fractionated granites. Thus, we suggested that the Mikengshan K-feldspar bearing granites are high fractionated and aluminous A-type granite. Their slightly high εNd(t) values (-3.4 to -4.6) indicate that the mantle components should have played a role during their formation. Taking into account regional igneous rocks and tectonic setting data, we suggest that the Mikengshan K-bearing granites were formed in an extensional setting, which was probably related to the roll-back of the subducted Paleo-Pacific plate. © 2018, Science Press. All right reserved.     

基于OGRE的三维场景可视化关键技术研究

OGRE是面向对象图形渲染的开源三维渲染引擎,具有面向场景和易扩展等特点。本文系统研究了基于OGRE三维渲染引擎的任意场景三维可视化的诸多关键技术,并以某学校为例,采用Sketch Up建模,以Microsoft Visual Studio 2010为开发环境,使用C++作为编程语言,最终实现了校园三维场景的三维可视化模拟和漫游等功能。     

Timing and identification of potential snow avalanche types: a case study of the central Tianshan Mountains

Landslides - Identifying and tracking the potential avalanche types is the first step toward characterizing an avalanche problem and a fundamental principle of effective avalanche risk management...     

利用气象要素计算五道梁地区土壤热流量的试验

根据五道梁地区1994—1997年的热流板测量土壤热流值,初步分析了该地区土壤热流随时间的变化特征。利用1994—1996年的月平均资料分别分析了总辐射、地表温度、地表温度和80 cm深度温度差和2 cm、10 cm深度的土壤热流的相关性,并建立了相应的回归方程;利用得到的回归方程对1997年的土壤热流作计算检验,就月平均资料来说,用总辐射和地温差来计算浅层土壤热流结果是比较可靠的。