一种基于LEO卫星信标的电离层层析成像新算法

LEO卫星信标是电离层监测的重要手段之一.利用电离层层析成像算法,LEO卫星信标能够实现区域电离层电子密度的快速重构.针对LEO卫星信标的特点,本文提出了一种函数基模型与像素基模型组合的电离层层析成像新算法.选择差分相对电离层总电子含量作为输入数据源,先通过函数基模型法获取电离层电子密度初始分布,再利用像素基模型法对初始分布进行二次迭代重构,该方法可有效降低电离层层析成像对背景电离层模型的依赖,同时能够实现电离层小尺度扰动结构的有效反演.利用数值仿真方法及低纬度电离层层析成像网的实测数据的反演结果验证了本文提出的新算法的可行性和可靠性.     

东亚赤道异常区电离层CT诊断──实验及初步结果

国际上第一个低纬电离层层析（ＣＴ）探测台链于１９９３年１１月建成，并开始数据采集．该ＣＴ台链沿１２０°Ｅ子午圈由６个卫星信标差分多普勒接收站组成，北起我国上海，南至菲律宾的马尼拉，纬度覆盖范围约２０°．该台链专为电高层赤道异常区电子密度大尺度结构ＣＴ成像而设计，其目的是监测研究赤道异常形态与动力学、电离层等离子体泡、行优以及暴时磁层－电离层－热层耦合过程等重要的赤道与低纬区电离层现象．本文介绍该低纬电离层ＣＴ实验的有关技术问题，包括接收台站布设、实验设备、数据采集软件和数据预处理方法．文中还给出利用ＣＴ技术，由实测斜电子含量数据反演电离层电子密度二维分布图像的几个实例．结果表明，利用低纬电离层ＣＴ台链可以有效地监测电离层赤道异常及其它低纬电高层电子密度大尺度结构的时空变化．     

一种海洋潜标适用的新型GPS信标机

本研究设计了一种潜标适用的新型信标机,它集成了GPS模块、数传模块、微处理器和压力开关等部件,可有效提高潜标回收过程中的目标定位能力。该信标机安装于潜标主浮体,通过压力开关控制电源。当主浮体位于海面时,信标机处于工作状态,它可以不断地将GPS位置数据通过无线传输方式向外发送,配套的接收端可以将接收的位置信息直观地显示在...     

Measurement of the group velocity of light in sea water at the ANTARES site

The group velocity of light has been measured at eight different wavelengths between 385 nm and 532 nm in the Mediterranean Sea at a depth of about 2.2 km with the ANTARES optical beacon systems. A parametrisation of the dependence of the refractive index on wavelength based on the salinity, pressure and temperature of the sea water at the ANTARES site is in good agreement with these measurements.     

多功能一体化信标机在海洋施工的应用

勘察人员在海洋地质勘察测量放样时,采用的定位导航设备通常是分体式信标机。分体式信标机主要由天线头、电缆、主机、数据线电源线、计算机和电瓶6大部件连接组成。在实际生产时,连接天线头和主机的电缆经常受到海水腐蚀而损坏,应用过程中经常需要搬运诸多装备,尤其风浪较大时候,操作过程烦琐且不安全,经市场调查,国内尚无专门的主机-天线一体化信标机。在此背景下,勘察处计划开发一款便携、操作方便的一体化信标机来解决上述问题,该系统不需要架设基站,并通过信标来发射差分信号,在离岸较远的海域使用星站差分服务提供高精度位置结果。经测试验证发现满足工程精度要求,提高海上定位的效率和安全性。     

基于单水声信标距离量测的匹配定位方法

水声通信和测距能力是实现水下航行器准确定位的重要技术手段。当前基于水声定位的方法主要有利用测距和测向功能的水声定位技术以及水声测距辅助导航技术,二者的系统物理复杂度都比较高。本文提出了一种基于单水声信标距离量测的匹配定位方法,航行器在水声信标测距覆盖范围内,利用航行过程中多次测距信息构建测距圆序列形成位置约束,基于航位推算导航信息,将航行器在连续测距时间段内的相对航迹在圆序列上进行最优匹配,从而获得位置估计,通过对测距误差进行补偿可进一步提升定位精度。本方法所需物理系统结构复杂度低、可操作性强,仿真实验表明,该方法可以独立实现较高精度的定位。     

信标GPS定位信号与测深仪水声信号的融合技术研究

以水下地形地貌测量为例,通过测量仪器硬件有效安装和倾斜改正,对信标GPS定位信号与换能器测深水声信号的空间位置在垂直轴上进行统一;以计算机API时钟作为时间基准,使定位信息和测深信息在时间轴上对齐;经过位置与时间信息融合后,形成空间匹配的三维数据.     

How Burial Time of Avalanche Victims is Influenced by Rescue Method: An Analysis of Search Reports from the Alps

Two hundred and seventeen avalanche reports from Switzerland and the Tyrol were used to investigate the influence of rescue method on the survival and burial time of avalanche victims. The probability of survival for victims rescued by their companion was higher (75, n=113) than for people found by an organised search team (30, n=104). Burial time and burial depth are the main factors, which decide whether a person is recovered dead or alive. People who were still alive were recovered significantly earlier and from a shallower burial depth than people who died in an avalanche. There is also a significant difference in the burial time dependent on whether companions or rescue teams carry out the search. In localising the site by means of sight/call or avalanche beacon by companions there is a clear relation between burial time and burial depth. For rescue teams, the relation between burial time and area of the avalanche is important. When working with avalanche dogs or probe lines there should be a clear correlation between burial time and area of the avalanche For dog teams arriving at the scene, there is a relation between search/excavation time and burial depth. Search time for tour skiers based on the information given will always be limited due to the burial depth of the victim. This means that the digging tools used are very important. The greatest problems facing rescue teams are limited transport capacity and the organisation of the whole mission over a large area. Therefore, speed and efficiency are of the utmost importance, when organising any search.     

基于定位信标的机动车辆辅助定位技术研究

采用计算机视觉技术解决机动车辆行使中定位问题是一项技术创新,运用定位信标的特殊性质和射频手段,选择合适的图象处理方法达到快速精确识别目标目的,在此基础上再量测为计算地理坐标所需要的几何元素,以上处理方法经过测试达到了机动车辆辅助定位的要求,系统地验证了方法和手段的有效性。     

Ray Theory Application in Long Baseline System

The long baseline (LBL) system is widely used to locate and track autonomous underwater vehicles (AUV) through acoustic communication.Three important issues are presented here in LBL system application with AUV.Those issues which regard the normal acoustic communication between LBL system and AUV are the depth of towed array,the length of beacon cable,and the effective area of the AUV.The first issue is the key of the LBL system,which ensures the normal communication between towed array and beacons.The second issue which impacts the normal communication from the AUV to beacons in available range should be considered after the first one has been settled.Then the last issue determines the safe work area of the AUV.The ordinary differential equations (ODE) algorithm of ray is deduced from Snell′s law.The ODE algorithm is applied to obtain sound rays from sound source to receiver.These problems are solved by the judgment that whether rays pinging from a sound source arrives at a receiver.The sea trial shows that these methods have much validity and practicality.