江苏灌河入海口附近重金属元素环境地球化学质量分析

以往对灌河口附近海域进行地球化学调查发现,海底沉积物及海水质量总体良好,但局部沉积物中Cr含量高于一类标准,Cu、As、Pb、Hg等其他重金属元素含量也明显高于其他地区,个别重金属元素已接近一类标准最高限,存在潜在生态风险。为进一步了解其与人类活动是否有关,对灌河靠近入海口40 km长的河水进行了地球化学调查,发现灌河河水中Hg、Cu、Pb等重金属元素存在一定程度的超标现象。结合其他证据认为,人类活动不仅对灌河下游河水质量产生了负面影响,还对入海口附近的海域环境质量产生了潜在威胁。借鉴内梅罗综合指数评价思路对灌河下游及入海口的重金属元素环境质量进行评价,并对如何降低、消除生态风险提出了若干建议。     

安徽贵池地区富硒土壤地球化学特征及开发利用潜力

为了解安徽贵池地区富硒土壤特征与潜力,服务当地富硒土地资源开发,选择贵池西部开展土壤地球化学测量试验,探讨Se、I等有益元素的富集特征、成因及潜力,Cd、As等有害元素的超标特征及成因等,结合研究区土壤中有益、有害元素特征,讨论富硒土地资源及其开发优势。发现表层和深层土壤中Se等有益元素含量总体较高,其中Se含量达到富硒土地标准的表层土壤点位占全部样品点位的76%;表层土壤中Cd含量超标的点位占48%,其他有害元素仅个别点位超标,Cd是制约该地区富硒土地资源开发的主要不利因素。在研究区圈定了61.4 km2的富硒土地资源,认为研究区东部土壤富硒的物质来源是二叠系灰岩,可以利用当地灰岩提升富硒土地资源品质,降低生态风险。     

基于STIRPAT模型的内蒙古沙漠化地区环境压力分析

实现经济与生态环境的协调发展，已经成为当前治理沙漠化的巨大挑战。如何定量分析人类活动和自然条件对环境的影响，是当前环境经济学界研究的热点问题。以内蒙古自治区71个沙漠化县为研究对象，以1986—2010年为研究区间做面板空间计量实证分析。选取了人口、富裕度、技术水平、风速和降水作为环境基础指标构建STIRPAT模型，从环境压力内在驱动角度定量分析不同的自然因素和人为因素对沙漠化地区环境的综合影响。结果表明：在观测数据范围内，富裕度、技术水平、风速和降水是内蒙古自治区环境压力的主要驱动因素；富裕度每增加1%，环境压力显著增加0.096%；技术水平每变化1%，将引起环境压力相应发生0.084%的变化；风速和降水每变动1%分别使得沙漠地区环境压力显著地增加0.640%和减少0.216%。     

BDS/GPS/GLONASS在密林地区组合定位性能分析

随着北斗卫星导航系统的建成与运行,目前已形成多系统导航定位的局面。基于短基线,首先对密林地区的GPS、BDS、GLONASS的卫星可见性以及伪距观测值的质量进行了简单的评价,然后分析了密林地区GPS、BDS、GLONASS单系统、双系统及三系统组合模式下单点定位及伪距差分定位性能。结果表明:在密林地区,GNSS多系统组合能够明显提高定位精度,GPS/BDS组合定位的精度优于GPS/GLONASS、BDS/GLONASS组合,而GPS/BDS/GLONASS的定位精度最高。     

Improved GNSS-based indoor positioning algorithm for mobile devices

GPS Solutions - The widespread use of global navigation satellite system (GNSS) receiver in mobile devices induces the adoption of effective GNSS-based indoor positioning algorithms exploiting...     

非线性基线长约束条件线性化近似对模糊度解算影响

GNSS动态相对定位中常附加非线性的基线长约束进行解算, 而LAMBDA方法只能处理无约束或者线性约束的模型, 为了应用LAMBDA方法, 应对非线性约束条件进行线性化近似。通常附加该约束后, 模糊度固定成功率会提高, 但对于超短基线有时反而会降低。何种条件下附加线性化近似的基线长约束条件可以提高模糊度固定成功率尚未有定论。本文基于附加基线长约束的GNSS相对定位数学模型, 推导基线长约束条件线性化近似余项对浮点解的最大影响值公式, 给出基线长约束能否线性化近似的诊断条件。当该条件满足时, 线性化近似余项影响可以忽略, 附加线性化近似的基线长约束可以改善浮点解解算精度, 提高模糊度固定成功率;若不满足, 则线性化近似余项影响可能不可以忽略, 附加约束会因浮点解有偏不能固定为正确的模糊度, 并通过算例验证了相关结论。     

Single epoch ambiguity resolution for Galileo with the CAR and LAMBDA methods

This paper investigates single epoch ambiguity resolution performance using Galileo four frequency data. Two commonly used ambiguity resolution methods are used in the tests, including the Cascade Ambiguity Resolution (CAR) and the Least-Squares Ambiguity Decorrelation Adjustment (LAMBDA) methods. For CAR method, four optimal combinations are carefully selected according to their wavelength to noise ratios and success rate for ambiguity fixing. The test results show, in general, the LAMBDA method performs better than the CAR method. The speed of ambiguity resolution is closely related to the carrier phase measurement precision. With carrier phase measurement precision of 3 mm, single epoch ambiguity resolution can be achieved at every epoch with simulated 1-s interval 24-h Galileo data (total epochs 86,400). With the increase of carrier phase noise, ambiguity resolution performances become worse. When the noise level is increased to 12 mm, single epoch ambiguity resolution can only be achieved about 50% of epochs.     

航空高光谱反演耕地土壤重金属分布特征——以苏北灌河地区为例

为探索航空高光谱遥感开展大比例尺、大面积土壤重金属含量和分布特征快速调查的技术方法和工作流程,以苏北灌河地区为例,利用国产高光谱成像仪和自主集成的航空高光谱遥感测量系统获取影像光谱数据,通过数据预处理、CARS特征波段选择及BP神经网络建模反演等方法,建立了从数据获取到数据分析评价的工作流程,反演了土壤重金属元素含量,展示了其空间分布特征。与传统地球化学调查数据进行对比分析,结果显示高光谱反演成果与地球化学调查的重金属浓度空间分布特征吻合度较高,验证了航空高光谱反演耕地土壤重金属分布特征的可靠性。在区域性耕地土壤重金属污染调查评价方面,航空高光谱遥感能够快速、及时地获取土壤污染及相关信息,并具有很好的实用性和经济性。     

Ambiguity validation with combined ratio test and ellipsoidal integer aperture estimator

To ensure reliable ambiguity resolution, ambiguity validation is an indispensable step. It has been a challenge for many years and is far from being resolved. Over the past years, various ambiguity validation methods have been proposed, such as F-ratio test, R-ratio test, difference test, projector test, ellipsoidal integer aperture (EIA) estimator and penalized integer aperture (PIA) estimator. In this paper, through analysis and testing, we find that, when the aperture region of EIA is not allowed to be overlapped, the efficiency of ambiguity resolution with EIA is low and it is not applicable to fast static positioning or real-time kinematic (RTK) applications. Then EIA with overlapped aperture regions is recommended and the resulted fail-rate becomes upper bound of the actual one. After that, it is suggested that combined use of overlapped EIA and R-ratio test can increase the reliability of ambiguity resolution. Finally, numerical tests are carried out based on practical buoy data and simulated Galileo data.     

The temporal change of driving factors during the course of land desertification in arid region of North China: the case of Minqin County

Taking the key research area in the arid region of North China—Minqin County—as a case, this paper analyzes the main factors impacting land desertification. Based on factor analysis method and the collection of data in the last 50 years, this paper researches the spatial changes of driving factors during the course of land desertification in Minqin, Gansu Province. The results of factor analysis indicate that the driving force of human factor on land desertification accounted for 56.33% in 1956–2004 and for 66.19% in 1981–2004, the driving force of nature factor on land desertification accounted for 11.29% in 1956–2004 and 8.11% in 1981–2004, and the synthesis of driving forces of human and natural factors accounted for 11.19% in 1956–2004 and for 14.88% in 1981–2004. This indicated that human driving force on land desertification was increasing in Minqin County gradually.