NOAA AVHRR数据的高精度导航定位

在ＮＯＡＡＡＶＨＲＲ数据的导航定位中,一般只进行卫星轨道根数调整和卫星时间漂移校正,而未考虑卫星姿态系统偏差的影响。该文在定量分析影响导航定位精度的主要因素基础上,提出了一种新的导航算法。该导航算法不仅对卫星时间漂移、卫星轨道根数进行约束最优调整,而且通过估算卫星姿态偏差将其融入到导航定位中加以校正。同时,将导航算法和卫星轨道计算、地面扫描点地理经纬度的计算方法以及参考图像的高精度配准等结合起来考虑,利用具有足够定位精度的１∶１００ 万数字地图数据和高分辨率Ｌａｎｄｓａｔ ＴＭ图像,提取地面控制点,使ＡＶＨＲＲ数据导航定位精度在整条轨道大范围内提高到１ 个像元,在星下点附近小于１ 个像元。     

天山地区ML≥3.6(K≥9.9)级地震目录定位精度及质量统计检验

采用统计检验方法 ,将天山地区 ML≥ 3.6 (K≥ 9.9)级地震目录与 ISC、NEIC、中国历史地震资料汇编、新疆地震目录进行对比检验 ,结果表明 :天山地震目录与 I、N、Z、X地震目录的发震时刻及经纬度值无明显差异 ;天山地震目录给出的发震时刻、震源位置精度比其它任何一个地震目录都高 ;参检的各地震目录给出的震源深度离散度大 ,稳定性差 ;天山地震目录具有较高的可信度和可靠性     

利用快电场变化脉冲定位进行云闪初始放电过程的研究

利用高时间精度GPS同步的雷电快天线电场变化测量仪等设备,在2004年夏季对甘肃中川地区雷暴的闪电放电特征进行了7站同步观测.在此基础上,发展了一种基于到达时间差的快天线电场变化脉冲定位方法,对8月20日一次强雷暴过程的5次云闪初始阶段产牛的快天线电场变化脉冲进行了三维定佗分析.结果表明:基于辐射源到达不同测站的时间差,能够对云闪产生的辐射源进行较好的定位,闪电的放电区域与雷暴的不同发展阶段密切相关.在雷暴发展的比较旺盛阶段,闪电的放电区域相对较高,对应的离地高度为3.3-6.4 km(此时对应的雷达回波顶高约9 km,回波强度在35 dBz以卜的回波顶高约7 km);在雷暴处于减弱和消敞阶段,闪电的放电高度降低,所分析的该阶段的其中1个云闪对应的离地高度为1.1-3.0 km(此时对应的雷达回波顶高约6 km,回波强度在35 dBz以上的回波顶高约3 km).与雷达同波的对比分析发现,云闪初始阶段的辐射脉冲源位置与强回波区具有较好的空间一致性,辐射脉冲源位置分别与25-50 dBz的回波区域相对成.这不仅在一定程度上表明了定化结果的可靠性,而且说明利用快天线电场变化测量仪组网观测对闪电进行定位跟踪有可能反映雷暴强中心的发展变化过程,同时也表明了利用快天线电场变化测量仪组网观测在强对流的监测和预臀中有一定的应用潜力.另外,定位误差的模拟试验表明,当雷电距观测网络较近时,定位误差较小,雷电距观测网络中心越远,定位误差越大.5次云闪的实际定他误差对比表明,模拟试验的定位结果在很大程度上能够有效地反映实际定位误差.这说明了该定位系统对位于探测网络上空或附近的雷电可以进行云内放电过程的较好的三维定位.     

Theoretical Error Analysis of the Accuracy of Focal Depth Determination of Near Earthquakes

Focal depth is one of the most difficult seismic parameters to determine accurately in seismology. The focal depths estimated by various methods are uncertain to a considerable degree,which affects the understanding of the source process. The influence of various factors on focal depth is non-linear. The influence of epicentral distance,arrival time residual and velocity model (crust model) on focal depth is analyzed based on travel time formula of near earthquakes in this paper. When wave propagation velocity is constant, the error of focal depth increases with the increase of epicentral distance or the distance to station and the travel time residual. When the travel time residual is constant,the error of focal depth increases with the increase of the epicentral distance and the velocity of seismic wave. The study also shows that the location error perhaps becomes bigger for shallower earthquakes when the velocity is known and the travel time residual is constant. The horizontal error caused by location accuracy increases with the increase of the epicentral distance,the travel time residual and the velocity of seismic waves,thus the error of focal depth will increase with these factors. On the other hand,the errors of focal depth will lead to change of the origin time,therefore resultant outcomes will all change.     

Between the Centre and the Periphery: the development of port trade in Darwin,Australia

Darwin, the capital of the Northern Territory, is a port city located in Australia's Top End and facing Southeast Asia. The distance from Darwin to Australia's main economic centres of Sydney and Melbourne is almost the same as to Singapore. This central geographical location has inspired the development of the Port and the City of Darwin from time to time while being held back by its remoteness, and especially the lack of an efficient railway link to Australia's major southern centres. The Port of Darwin has been redeveloped with the vision of repositioning the City of Darwin as Australia's gateway to Asia which it was expected to achieve with the completion of the transcontinental railway link from Adelaide to Darwin. This paper analyses trade and cargo movements for the Port of Darwin between 2000 and 2009—5 years for each period before and after the availability of intermodal transport—and examines the processes by which transformation of the gateway is actually occurring. The evidence to date, however, suggests that the landbridge development has had little material effect in terms of trans-shipments and throughputs for the Port of Darwin. The volume of container trade and interstate export and import cargo that passes through the port has in fact declined since the availability of the transcontinental railway in 2005.     

Spatio-temporal features and the dynamic mechanism of shopping center expansion in Shanghai

Since the first modern shopping centre was built in the United States in the 1920s, shopping centres have gradually become representative patterns of economic growth and consumerism in the United States, and these patterns are now trending globally. Shopping centres have demonstrated tremendous development potential since their initial entry into China in the 1990s. Shanghai is the most economically prosperous city in China, and the development and evolution of its shopping centres reflect the trend in China's commercial real estate development. Therefore, based on the central-place and agglomeration economy theory, this paper quantitatively measures and analyses the spatial gravity, extending direction, agglomeration characteristics and hierarchical structure of Shanghai's shopping centres using GIS (Geographic Information Systems) and spatial analysis. Moreover, this paper analyses the dynamic mechanism of urban development and its patterns of centripetal and centrifugal movement. The results demonstrate the following. (1) The spatial gravity points are located in the districts of Huangpu, Luwan and Xuhui in the city centre and within the inner ring. In addition, there is a trend to be gradually near the middle ring, exhibiting an obvious tendency from the northeast to the southwest. (2) Shopping centres in Shanghai exhibit a clustered distribution in the centres of urban areas, which form numerous business districts that extend in the same direction. (3) The hot spot analysis is a very effective method for identifying the hierarchy of business circles. (4) Planning by the government is the most important external impetus, and commercial agglomeration is the internal force determining the spatial expansion of shopping centres. Additionally, urban transportation patterns have an obvious influence on the spatial morphology of shopping centres. (5) Over the last two decades, the spatial development of Shanghai's shopping centres has reached a balance between the centripetal and centrifugal forces. In other words, we have not observed a tendency towards suburbanization, which indicates that Shanghai's shopping centres are still in the early stages of development. Therefore, future shopping centres may be primarily located in the stretch or peripheral zones of the city.     

Distance predicting functions and applied location-allocation models.

Distances between demand points and potential sites for implementing facilities are essential inputs to location-allocation models. Computing actual road distances for a given problem can be quite burdensome since it involves digitalizing a network, while approximating these distances by l _p -norms, using for instance a geographical information system, is much easier. We may then wonder how sensitive the solutions of a location-allocation model are to the choice of a particular metric. In this paper, simulations are performed on a lattice of 225 points using the k-median problem. Systematic changes in p and in the orientation of the orthogonal reference axes are used. Results suggest that the solutions of the k-median are rather insensitive to the specification of the l _p -norm. Received: 12 October 1998/Accepted: 17 September 1999     

导航地图情境建模

目前,尽管形形色色的导航地图产品已经成为人们日常出行的必备帮手,但是实用性不强、效率偏低是普遍存在的一种现象,严重降低了人们对地图的信任程度。为此,本文引进情境理论,通过分析其与导航地图之间的联系,指出情境建模在沟通用户、环境与设备之间作为桥梁的重要意义,并将活动从一般情境信息中剥离出来,确定了导航地图情境建模基本原理,从通用情境信息建模和导航活动建模2个方面详细阐述了导航地图情境建模的方式与方法,为后续研究情境推理与表达奠定基础。     

1994年4月的SL9彗星观测

１９９４年４月１２日晨，我们对Ｓ９彗星进行了成功的观测．观测使用云南天文台一米望远镜和加了缩焦器的Ⅱ号ＣＣＤ系统．照相机像素为５１２×５１２，视场约７’×７’．在近两小时的不同时刻的四张照片中，观测到了彗星２１颗碎核中的主要部份及其运动．本文介绍了此次观测情况和资料处理，并给出对ＳＬ９各彗核的位置和亮度的测量结果．     

城市居民住宅区位选择的因子分析

随着我国住房制度的改革 ,城市居民个人消费成为我国房地产市场的消费主体 ,居民对住宅区位选择行为由过去的被动接受转变为主动选择。本文主要研究在这种新的住房制度下 ,影响城市居民住宅区位选择的因子。作者认为 ,房价的高低、住宅区位的交通通达性、环境条件是决定城市居民住宅区位选择的客观条件 ,居民自身的社会、经济、文化等特征、以及对不同住宅区位和环境的偏好也左右着住宅区位选择过程和结果。