载波/多普勒平滑伪距在Android手机中的定位实现     

张书维  高井祥  赵龙  李增科 《测绘通报》2020,(4):63-67

针对Android手机GNSS伪距定位精度较低的问题，利用手机端观测信息，通过载波相位/多普勒平滑伪距改善手机端伪距观测值的质量，从而达到提高定位精度的效果。首先给出了Android手机GNSS原始观测量的获取方法，然后推导了载波相位平滑伪距和多普勒平滑伪距算法模型，并设计合理有效的试验对算法的精度进行评定。试验结果表明：在手机端静态定位中载波相位和多普勒平滑算法均可提高原始伪距的定位精度，且多普勒平滑算法表现更优；在手机端动态定位中多普勒平滑算法可获得比原始伪距更优的定位精度，但是载波相位平滑算法较原始伪距更差；由于硬件的制约手机端周跳和信号失锁严重，占比超过50%，载波相位在手机端的可用性较低；多普勒平滑算法的最优平滑时间常数小于等于10 s，具有实时动态定位的巨大潜力。  相似文献   

Field Measurement of Suction, Water Content, and Water Permeability   总被引：1，自引：0，他引：1  

Alessandro Tarantino  Andrew M. Ridley  David G. Toll 《Geotechnical and Geological Engineering》2008,26(6):751-782

This paper presents a review of techniques for field measurement of suction, water content, and water hydraulic conductivity (permeability). Main problems in the use of field tensiometers are addressed and hints on how to improve tensiometer performance are given. Advantages and limitations of instruments for indirect measurement of suction including electrical conductivity sensors, thermal conductivity sensors, dielectric permittivity sensors, filter paper, and psychrometer are discussed. Techniques for water content measurement based on dielectric methods are then presented. These include time and amplitude domain reflectometry and capacitance. Finally, a brief overview of methods for measurement of water permeability in the field is presented.  相似文献   

Inter sensor comparison between RESOURCESAT LISS III, LISS IV and AWiFS with reference to coastal landuse/landcover studies     

H.B. Chauhan  R.M. Dwivedi 《International Journal of Applied Earth Observation and Geoinformation》2008,10(2):181-1

Coastal zone assumes importance due to high productivity of ecosystems, man-made developmental activities, natural hazards and dynamic nature of the coast. As costal ecosystems are unique and fragile, understanding the impact of developmental activities on the sustainability of the coastal zone is very important. Remote sensing, because of repetitive and synoptic nature is an ideal tool for studying this. Time series data analyses for monitoring coastal zone require different type of sensors. Present study deals with atmospheric correction of satellite data, reflectance, selection of coastal features like, mudflat, mangroves, vegetated dune, coastal water, etc. and their inter-comparison using different sensor data of RESOURCESAT sensors. Reflectance values give better separateability for various coastal features in comparison to DN values. LISS IV can be used in place of LISS III or merged (LISS III + PAN) for long-term coastal zone studies.  相似文献   

如何面对潜在客户的拒绝     

于春红 《气象研究与应用》2003,24(3):59-60

电话营销作为广告营销的一种主要方式,在广告营销过程中起着重要作用,根据这一营销特征,就如何面对客户在电话中拒绝提出相应的应对技巧,以赢得客户。  相似文献   

SMA-MR复合型阻尼器   总被引：5，自引：0，他引：5  

卞晓芳  薛素铎 《世界地震工程》2004,20(2):23-29

利用形状记忆合金超弹性、形状记忆特性和MR液的材料特性，提出了SMA-MR复合阻尼器，建立了阻尼器的理论模型。通过输入正弦波得到小震、大震时相应的滞回曲线，并对一单层框架进行输入El Centro地震波下的减震效果分析，比较了SMA-MR阻尼器、仅有SMA和仅有MR作用下的减震效果。结果表明，所设计的SMA-MR阻尼器具有卓越的阻尼性能，对大震、小震的控制实现了自适应的智能性。  相似文献   

智能卡和出租车轨迹数据中蕴含城市人群活动模式的差异性分析     

郑晓琳  刘启亮  刘文凯  吴智慧 《地球信息科学学报》2020,22(6):1268-1281

当前采用交通流数据量化城市人群活动模式研究已经取得了丰硕的研究成果,但是对于同一区域、同一时段不同类型交通流数据反映城市人群活动模式的共性与差异性仍然知之甚少,直接影响了城市人群活动模式挖掘结果的可解释性与实际应用效果。为此,本文旨在对目前广泛采用的智能卡数据（公交和地铁刷卡）和出租车轨迹数据2种重要的交通流数据,从时空分布模式的差异性、行程距离及距离衰减效应的差异性、空间社团结构的差异性3个方面,探索二者反映城市人群活动模式的差异性：① 采用北京市六环以内区域2016年5月9日至15日的智能卡和出租车轨迹数据进行实验分析,研究发现：① 2种交通流反映出行需求的空间分布呈现出高度相关性,但是在同一空间单元上,2种交通流反映出行需求的时间相关性较低;② 2种交通流的使用率在不同空间位置存在明显差异,仅在城市中心区域使用率较为均衡;③ 2种交通流反映人群行程距离的空间分布、距离衰减效应存在明显差异,公共交通对于促进长距离出行更为重要;④ 从2种交通流发现的空间社团结构都显示了城市的多中心结构特征,但是二者发现社团结构存在的差异性表明两种交通方式对城市空间交互起着不同的作用。本研究有助于深入理解多源交通流反映城市人群活动的内在机理,提升城市人群活动模式在城市规划、交通管理等领域的应用效果。  相似文献   

基于移动端的“智慧城市与地理国情一张图系统”设计及其应用     

薛晓轩  徐凯  李俊卿 《测绘与空间地理信息》2016,(11):147-149

系统把智慧城市建设与地理国情应用完美结合,形成时空一体、二三维一体的集成多源数据的一张图;开发IPAD版系统,把PC端的数据处理向移动端适时展现。系统具有国情普查数据的展示和分析、专题地图展示、电子地图、三维模型展示、轨迹记录,以及其他GIS基本功能。在屏幕上任意点取闭合图形,就会实时显示选定图形范围内的国情数据及统计分析数据。辅助决策者又好又快地进行科学决策。  相似文献   

Opportunistic natural experiments using digital telemetry: a transit disruption case study     

Kevin Stanley  L. Kurt Kreuger  Priyasree Bhowmik  Narjes Shojaati  Alexa Elliott 《International journal of geographical information science》2016,30(9):1853-1872

ABSTRACT

In the past decade society has entered a technological period characterized by handheld computing that supports input and processing from numerous sensors. Today’s mobile phones offer the ability to integrate input from sensors monitoring various external and internal sources (e.g., accelerometer, magnetometer, microphone, GPS, wireless Internet, and Bluetooth). Furthermore, these raw inputs can be integrated and processed in ways that can offer novel representations of human behaviour. As a result, new opportunities to examine and better understand human spatial behaviour are available; one such application is the constant monitoring of a group of people over an extended period of time. Such a research setting lends itself to natural experiments that emerge as a result of regular and on-going observations. We report here on the observation of a natural experiment that took place in the context of a month-long monitoring study of 28 participants using mobile phone-based ubiquitous sensor monitoring. The implications for public health and transportation planning are discussed.  相似文献   

上海中心城就业中心体系测度————基于手机信令数据的研究   总被引：17，自引：2，他引：15  

丁亮  钮心毅  宋小冬 《地理学报》2016,71(3):484-499

利用手机信令数据识别上海市域内手机用户的工作地和居住地,获取就业者的通勤数据,测度上海中心城的就业中心体系.首先用就业者工作地数据生成就业密度分布图,基于中心城的就业密度识别就业中心.随后,用就业者工作地和居住地数据分别从就业密度和通勤联系两方面测度各中心的能级,分析各中心的腹地和势力范围.研究发现:① 上海中心城的就业中心呈主中心强大的弱多中心体系;② 就业密度越高的中心与其他地区的通勤联系一般也越强,但通勤联系在各中心间的差异更显著;③ 能级越高的中心腹地面积越大,但势力范围不一定越大;④ 相比于能级,职住功能混合度对职住平衡的影响更大;⑤缺少就业中心的地区势力范围呈交替状.本研究一定程度上能有助于解决既往就业中心体系研究因空间单元较大,缺少通勤数据在中心识别,通勤联系测度等方面受到的局限,希望能为构建上海中心城就业多中心体系提供帮助.  相似文献   

Advances and Trends in Atmospheric Measurement by Smartphones*     

Xichuan Liu  Taichang Gao  Binsheng He  Lei Liu  Min Yin  Kun Song 《地球科学进展》2018,33(12):1223-1236

With the development and popularization of smartphones and embedded sensors, a non-professional atmospheric measurement method by using smartphones carried by the public has been proposed recently. Without extra dedicated instrument, this method has many advantages, such as low hardware cost, high spatio-temporal resolution, and wide coverage, and it can supplement the professional atmospheric measurement methods, which has broad applications in the meteorological operation, scientific research, public service, and other fields. At present, the research on the non-professional atmospheric measurement in China is limited. In order to make full use of this method, this paper briefly outlined the states of existing smartphones and embedded sensors, highlighted the measurement of precipitation, air temperature, pressure, aerosols, and radiation by smartphones. To promote the development of smartphones for atmospheric measurement, future research should focus on mechanism study, available sources exploration, data quality control, big data processing, joining and matching with operation, research and service, etc.  相似文献