Precise geodesy with the Very Long Baseline Array

We report on a program of geodetic measurements between 1994 and 2007 which used the Very Long Baseline Array (VLBA) and up to ten globally distributed antennas. One of the goals of this program was to monitor positions of the array at a 1 mm level of accuracy and to tie the VLBA into the international terrestrial reference frame. We describe the analysis of these data and report several interesting geophysical results including measured station displacements due to crustal motion, earthquakes, and antenna tilt. In terms of both formal errors and observed scatter, these sessions are among the very best geodetic very long baseline interferometry experiments.     

A non-iterative and non-singular perturbation solution for transforming Cartesian to geodetic coordinates

The Cartesian-to-Geodetic coordinate transformation is re-cast as a minimization algorithm for the height of the Satellite above the reference Earth surface. Optimal necessary conditions are obtained that fix the satellite ground track vector components in the Earth surface. The introduction of an artificial perturbation variable yields a rapidly converging second order power series solution. The initial starting guess for the solution provides 3–4 digits of precision. Convergence of the perturbation series expansion is accelerated by replacing the series solution with a Padé approximation. For satellites with heights < 30,000 km the second-order expansions yields ~mm satellite geodetic height errors and ~10⁻¹² rad errors for the geodetic latitude. No quartic or cubic solutions are required: the algorithm is both non-iterative and non-singular. Only two square root and two arc-tan calculations are required for the entire transformation. The proposed algorithm has been measured to be ~41% faster than the celebrated Bowring method. Several numerical examples are provided to demonstrate the effectiveness of the new algorithm.     

深圳区域椭球确定与坐标转换方法研究

提出了单点平移多点调整确定区域椭球的方法,构建了通过GPS水准点确定已知椭球面与似大地水准面之间倾斜关系的数学模型,实现了深圳独立坐标系与空间大地坐标系之间的无精度损失、无多义性转换。     

地籍数据建库方案的探讨

通过对建立"地籍数据库"的一些体会和认识,探讨地籍数据转换、CAD图形系统生产的矢量数据转换到地籍数据库中的一些技术路线,探索利用CAD系统生产地籍数据库的方法.     

平面影像到QTM像元的转换算法及精度分析

平面影像数据到四元三角网(Quaternary Triangular Mesh,QTM)像元的转换是实现全球QTM格网影像无缝建模的首要任务。提出基于面积权的数据转换方法,给出不同类型的权重及格网值的计算,并利用ArcGIS中256级灰度的Wsiearth.tif图像数据分析了转换精度。结果表明:将4 km分辨率的影像数据转换到12层的QTM像元时,转换误差在0~2灰度内占96.27%,对一般应用的影响可以忽略不计。     

从地方坐标系到2000国家大地坐标系的转换方法

探讨了我国原有地方坐标系与CGCS2000坐标系的定义差别,在我国相关学者研究成果的基础上,设计一种基于布尔莎七参数转换模型的坐标系统转换方法,可以实现除高等级大地控制点之外的各种地理信息数据从原有地方坐标到CGCS2000坐标的快速转换。     

Evaluation of the wave transformation in an open bay with two spectral models

An evaluation of two state of the art phase averaged wave models for the transformation scale, SWAN and STWAVE, is carried out in the present work. The target area is the Obidos Bay located in the central part of the Portuguese continental nearshore. The wave input for the two models is provided by an offshore buoy. In order to compare the nearshore outputs of the wave models against in-situ measurements, a directional buoy and an ADCP, operating in intermediate water depth, are used. The wave parameters considered for comparisons are significant wave height, peak period and wave direction. Sensitivity analyses studies and evaluations in the spectral and geographical spaces concerning the results of the two models are also carried out in both intermediate and shallow water. The present study provides some information on the performances of the two wave models in different forcing conditions as well as on their sensitivity in relationship with various input parameters and some physical processes. STWAVE appears to be faster and more robust than SWAN, which on the other hand has more options and flexibility. In statistical terms the results are comparable.     

Nonlinear Dispersion Relation in Wave Transformation

1 .Ｉｎｔｒｏｄｕｃｔｉｏｎ1ＴｈｉｓｗｏｒｋｗａｓｆｉｎａｎｃｉａｌｌｙｓｕｐｐｏｒｔｅｄｂｙｔｈｅＮａｔｕｒａｌＳｃｉｅｎｃｅＦｏｕｎｄａｔｉｏｎｏｆＣｈｉｎａ (ＧｒａｎｔＮｏ .4 0 0 760 2 6ａｎｄ 4 0 0 760 2 8) Ｃｏｒｒｅｓｐｏｎｄｉｎｇａｕｔｈｏｒ.Ｅ ｍａｉｌ:ｒｊｌｉ@ｈｈｕ .ｅｄｕ .ｃｎ　　Ｉｔｉｓａｖｅｒｙｕｓｅｆｕｌａｎｄｅｆｆｅｃｔｉｖｅｗａｙｔｏａｄｊｕｓｔｔｈｅｗａｖｅｄｉｓｐｅｒｓｉｏｎｒｅｌａｔｉｏｎｆｏｒｔｈｅｓｔｕｄｙｏｆｔｈｅｎｏｎ ｌｉｎｅａｒｉｔｙｏｆｗａｖｅｐｒｏ…     

潮滩“干湿过程”模式下营养盐的迁移、转化微观实验模拟

潮滩是联系陆地生态系统和海洋生态系统的交互过渡带,与陆地湖泊、河流和深海系统相比有其特殊性和复杂性.在潮汐作用下由于潮滩受潮水周期性浸没和暴露的影响,使得潮滩界面成为一个典型的沉积物-水-气周期性交互作用界面.潮水的周期性涨退将诱使潮滩沉积物中发生一系列的物理、化学和生物变化[1].在暴露期间,因蒸发作用潮滩沉积物可能会发生失水现象,并引起沉积物孔隙水发生迁移和水溶性物质扩散梯度发生变化[2,3].在暴露失水过程中,空气也可能会占据沉积物间隙,并引起潮滩沉积物物理结构发生变化,加剧了沉积物-气界面之间需氧过程的发生[4,5].     

国家西部测图工程成果1980西安坐标系与CGCS2000国家大地坐标系转换方案的设计与实现

通过对西部测图工程成果数据的坐标转换试验,提出了一种有效的坐标转换方案。文中详细探讨了转换过程中的技术要点、解决方案以及在VB．NET中代码实现的过程。