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1.
一种北斗联合低轨星座的导航增强方法研究 总被引:1,自引:0,他引:1
单纯依靠北斗导航系统提供定位导航授时服务,存在卫星信号落地功率低、易受遮蔽和阻断的不足。针对此问题,研究了一种北斗联合低轨星座实现导航增强的系统架构;提出了一种新的适应严重遮蔽或干扰条件下,基于到达时间(TOA)和到达频率(FOA)联合观测的定位解算算法;对高中低轨混合星座条件下的覆盖特性和精度衰减因子进行了仿真分析。分析结果表明,用户可见星数平均增加了64.2%,位置精度衰减因子(PDOP)平均改善了28.7%。研究结果可为下一代北斗的论证设计与研制建设提供参考借鉴。 相似文献
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结合GPS测量的特点,较为详细的探讨了GPS静态相对定位和RTK(实时动态定位)技术在高速公路测量中的应用,并通过实例证明GPS用于高速公路测量是完全可行的,它在很大程度上可以提高测量的工作效益并节省费用。 相似文献
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Roads represent an important landscape element affecting both biotic and abiotic components. Alteration of soil properties along roads (addition of nutrients) is assumed to have a great impact on vegetation structure especially in nutrient poor ecosystems. Existing studies focus mainly on road dust. In our study we assessed the overall effects of roads upon adjacent alpine tundra vegetation and soils in Krkonoše Mts, Czech Republic. Our aims were to (1) reconstruct the road-related changes using aerial data and GPS mapping to study colonization of roadside plant species; (2) assess the road effects on physical-chemical soil properties and vegetation composition along transects; and (3) propose conservation measures to stop further damage. Changes were reconstructed from historical multispectral aerial photography (1986 to 1997), measured by GPS device (1997, 2004), and accompanied by detailed soil (1998, 2000 and 2001) and vegetation (2000 and 2004) surveys along transects. Along alkaline roads, fast and profound shifts in physical-chemical soil properties (pH increased from 3.9 up to 7.6, base saturation from 9-30% up to 100%), and species composition were recorded. The roadside vegetation doubled in area during the studied decade. Stress-tolerant tundra species were replaced by meso- to nitrophilous species and species preferring man-made habitats. The intensity of changes depended significantly on the type of road material and the position relative to the road (slope position, distance from the road). Our findings support the assumption that alkaline gravel is the main cause of changes along roads in the area, and indicate the leading role of water transport in the soil and consequent vegetation alteration. To prevent the further damage we recommended replacement of alkaline gravel by granite, even though expensive and technically complicated. Based on our recommendations, the National Park authorities started to reconstruct the trails, although recovery is expected to be slow. 相似文献
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移动定位大数据包括手机信令数
据、移动互联网LBS数据等类型,是表示个
体活动时空特征的轨迹数据。在移动定位
大数据中依据轨迹点的时空特征规律能识
别出个体活动的居住、工作、游憩等特征
点,计算上述活动的空间分布特征,进而获
得居住、工作、游憩等功能之间联系的流向
和流量特征,获得传统数据无法反映的城
市功能空间分布以及城市功能联系的时空
特征。由此,移动定位大数据支持建成环境
规划设计有密度出发和联系出发两种应用途
径。联系出发的途径能支持区域城市关联、
职住空间关系、城市中心体系、设施服务水
平等方向;密度出发的应用途径能支持城
市人口规模、街道活力分析等方向。移动定
位大数据测算居民活动特征还只是一种推
测,在应用方法上要避免“黑箱”方式,对移
动定位大数据测算结果一定要结合传统数
据进行校核,提高可靠性。 相似文献
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High-accuracy positioning is not only an essential issue for efficient running of high-speed train (HST), but also an important guarantee for the safe operation of high-speed train. Positioning error is zero when the train is passing through a balise. However, positioning error between adjacent balises is going up as the train is moving away from the previous balise. Although average speed method (ASM) is commonly used to compute the position of train in engineering, its positioning error is somewhat large by analyzing the field data. In this paper, we firstly establish a mathematical model for computing position of HST after analyzing wireless message from the train control system. Then, we propose three position computation models based on least square method (LSM), support vector machine (SVM) and least square support vector machine (LSSVM). Finally, the proposed models are trained and tested by the field data collected in Wuhan-Guangzhou high-speed railway. The results show that: (1) compared with ASM, the three models proposed are capable of reducing positioning error; (2) compared with ASM, the percentage error of LSM model is reduced by 50.2% in training and 53.9% in testing; (3) compared with LSM model, the percentage error of SVM model is further reduced by 38.8% in training and 14.3% in testing; (4) although LSSVM model performs almost the same with SVM model, LSSVM model has advantages over SVM model in terms of running time. We also put forward some online learning methods to update the parameters in the three models and better positioning accuracy is obtained. With the three position computation models we proposed, we can improve the positioning accuracy for HST and potentially reduce the number of balises to achieve the same positioning accuracy. 相似文献
10.
《Measurement》2015
Structural failures (bridge or building collapses) and geohazards (landslides, ground subsidence or earthquakes) are worldwide problems that often lead to significant economic and loss of life. Monitoring the deformation of both natural phenomena and man-made structures is a major key to assessing structural dynamic responses. Actually, this monitoring process is under real-time demand for developing warning and alert systems.One of the most used techniques for real-time deformation monitoring is the Global Navigation Satellite System (GNSS) real-time procedure, where the relative positioning approach, using a well-known reference station, has been applied.This study was conducted to evaluate the actual quality of the real-time kinematic Precise Point Positioning (PPP) GNSS solution for deformation monitoring, where it can be concluded that a promise tool is under development and should be taken into account on actual and near future real-time deformation monitoring studies and applications. 相似文献