GPS高程区域似大地水准面分区方法

由于坐标系统不同,用GPS进行高程测量时必须首先进行高程拟合确定似大地水准面。高程拟合的方法有多种,当测区面积不大时,这些方法在一定程度上都能取得好的效果,但当测区面积很大时,直接应用这些方法往往难以取得好的结果。实际操作中对于测量面积很大时,往往采用分区拟合的方法。目前分区主要有两类方法:一是根据测区的实际地形起伏情况划分;二是根据支撑点的高程异常来划分。按地形分区,简捷易行常被采用,但有时精度难保证;按支撑点划分,在地形复杂地区,其高程异常起伏不定,根据相邻点的高程异常的差值很难定出分区情况。本文提出一种新的思路,即首先依据EGM96去掉高程异常中的中长波部分,再用残余的高程异常做等值线图,根据等值线图再进行分区。由于等值线图能反映高程异常的细部结构,根据等值线图进行的分区能保证每个分区中高程变化的单调性,因而有利于高程的拟合。实例表明,该方法能取得良好的拟合效果。     

Recent Changes Occurred in the Terminus of the Debris-covered Bilafond Glacier in the Karakoram Himalayas Using Remotely Sensed Images and Digital Elevation Models (1978-2011)

Recent changes occurred in terminus of the debris-covered Bilafond Glacier in the Karakoram Range in the Himalayas, Northern Pakistan was investigated in this research. Landsat MSS, TM and ETM＋ images were used for this study. Digital elevation models derived from ASTER GDEM and SRTM were also utilized. Visible, infrared and thermal infrared channels were utilized in order to get accurate glacier change maps. Three methods were tried to map this debris-covered glacier in this research. The glacier has been mapped successfully and the changes in the glacier terminus from 1978 to 2011 have been calculated. Manual, semi-automatic and thermal methods were found to give similar results. It was found that the glacier has undergone serious ablation during this period despite of the fact that many of the larger glaciers in the Hindu Kush and Karakoram mountain regions in the Upper Indus Basin were reported to be expanding. The terminus has been moved back about 600 meters during this period and there was an abrupt change in the glacier terminus during 1990-2002. We propose that debris thickness is not the only factor that influences the glacier ablation but the altitude of the debris-covered glacier as well. Many glaciers in the Karakoram region reported to be expanding were having higher altitudes compared to the study area.     

Volume estimation of small scale debris flows based on observations of topographic changes using airborne LiDAR DEMs

This paper describes a geographic information system(GIS)-based method for observing changes in topography caused by the initiation, transport, and deposition of debris flows using highresolution light detection and ranging(LiDAR) digital elevation models(DEMs) obtained before and after the debris flow events. The paper also describes a method for estimating the volume of debris flows using the differences between the LiDAR DEMs. The relative and absolute positioning accuracies of the LiDAR DEMs were evaluated using a real-time precise global navigation satellite system(GNSS) positioning method. In addition, longitudinal and cross-sectional profiles of the study area were constructed to determine the topographic changes caused by the debris flows. The volume of the debris flows was estimated based on the difference between the LiDAR DEMs. The accuracies of the relative and absolute positioning of the two LiDAR DEMs were determined to be ±10 cm and ±11 cm RMSE, respectively, which demonstrates the efficiency of the method for determining topographic changes at an scale equivalent to that of field investigations. Based on the topographic changes, the volume of the debris flows in the study area was estimated to be 3747 m3, which is comparable with the volume estimated based on the data from field investigations.     

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简述摄影测量与遥感中的4D产品制作

简介摄影测量与遥感中的4D产品的制作方法,以及4D包括的内容。     

利用神经网络建立GPS网络RTK的双差对流层误差模型

为减小对流层误差改正数中系统偏差的影响以提高对流层改正精度,提出了基于神经网络的顾及空间的对流层误差建模模型,该模型的对流层延迟误差改正在网内外精度均达5 cm。     

GNSS+SINS组合导航地固系高度阻尼算法

GNSS+SINS组合导航在地固系中计算有诸多优点,但GNSS信号缺失时的高度阻尼比较复杂。本文从空间直角坐标系与大地坐标系的关系出发,结合地固系捷联惯导的导航方程,提出了一种地固系高度阻尼算法。经仿真测试证明,应用此算法在地固系高度阻尼,可以达到与导航系相同的效果,证明了算法的有效性。     

1985国家高程基准与全球似大地水准面之间的系统差及其分布规律

将由大地高和正常高导出的几何高程异常与由位系数模型计算得到的物理高程异常进行比较,求出1985国家高程基准与全球似大地水准面之间的系统差,并分析其分布特性.为抵制异常值的影响,引入"抗差等价权".利用分布全国大陆范围的GPS网949个点的GPS/水准数据和地球重力场模型EGM96、DQM99A,求出1985国家高程基准点与WGS84定义的似大地水准面之间有35.7 cm的垂直偏差,1985国家高程基准面的系统差自东向西、自南向北明显增大,给出相应的数学模型.     

RTCM数据格式实时处理方法应用

＂GNSS基准实时数据采集、传输与监测技术＂课题要求实现多台GPS接收机秒级的数据实时采集与解析。针对这一问题,分析了RTCM3.1数据格式,介绍了CRC-24校验算法,详细阐述了数据在缓冲区中实时存储的实现方法,分析了原始观测数据的还原算法及数据边界情况的处理方法;在TCP/IP协议模式下实现了天宝NetR8接收机的实时数据采集,并基于RTCM3.1实现了二进制数据流的实时解析。同天宝GPSNet软件进行比对,结果一致,程序运行稳定。