Preprocessing of gravity gradients at the GOCE high-level processing facility

One of the products derived from the gravity field and steady-state ocean circulation explorer (GOCE) observations are the gravity gradients. These gravity gradients are provided in the gradiometer reference frame (GRF) and are calibrated in-flight using satellite shaking and star sensor data. To use these gravity gradients for application in Earth scienes and gravity field analysis, additional preprocessing needs to be done, including corrections for temporal gravity field signals to isolate the static gravity field part, screening for outliers, calibration by comparison with existing external gravity field information and error assessment. The temporal gravity gradient corrections consist of tidal and nontidal corrections. These are all generally below the gravity gradient error level, which is predicted to show a 1/f behaviour for low frequencies. In the outlier detection, the 1/f error is compensated for by subtracting a local median from the data, while the data error is assessed using the median absolute deviation. The local median acts as a high-pass filter and it is robust as is the median absolute deviation. Three different methods have been implemented for the calibration of the gravity gradients. All three methods use a high-pass filter to compensate for the 1/f gravity gradient error. The baseline method uses state-of-the-art global gravity field models and the most accurate results are obtained if star sensor misalignments are estimated along with the calibration parameters. A second calibration method uses GOCE GPS data to estimate a low-degree gravity field model as well as gravity gradient scale factors. Both methods allow to estimate gravity gradient scale factors down to the 10⁻³ level. The third calibration method uses high accurate terrestrial gravity data in selected regions to validate the gravity gradient scale factors, focussing on the measurement band. Gravity gradient scale factors may be estimated down to the 10⁻² level with this method.     

月面形貌的3维可视化算法

基于大范围地形可视化算法研究的基础上,对平面geometry clipmaps算法进行改进,利用GPU的顶点着色器实现平面地形向球面地形的投影变换,并综合利用球面视域裁剪、球面视点控制等技术,使geometry clipmaps算法适用于球面海量地形数据的3维可视化;收集处理月球全球影像和形貌高程数据,对算法进行验证,实现月球表面形貌的实时动态3维可视化.试验表明:绘制算法可不受数据量大小的限制、绘制效率高、效果逼真,但存在两极变形较大的缺点.

Abstract：

Based on the study of visualization arithmetic of large area terrain, plane geometry clipmaps algorithm is improved. Projection transformation from plane landform to sphere landform was realized by using GPU vertex shader. In that improved algorithm, methods such as sphere vision field culling and sphere viewpoint control are used.That makes geometry clipmops algorithm more effective in 3D visualization of massive sphere terrain data. The whole moon image and DEM data are collected and disposed, which are used to verify the capability of that algorithm, realizing dynamic and real time 3D visualization of moon surface. The experiments show that the graphic algorithm isn't limited by data quantity, which is of high efficiency and reality simulation, but the two-pole distortion is serious.     

基于全站仪观测数据的三维平差模型及数据处理

建立基于全站仪多维观测数据的三维网平差模型,用VisualBasic语言编制计算程序,使其自动完成控制网的平差,解决实际应用中全站仪采集数据和成果处理中存在的问题,指导测绘生产,使全站仪更方便地用于地形控制测量、工程控制测量等测绘工程中。     

建筑物沉降观测技术方法探讨

随着城市建设的迅猛发展,城市规模越来越大,建筑物越来越高,由此带来的安全隐患越来越大,由于高层建筑一般采用桩基基础,且荷载较大,对高层建筑的内部基础和设备的位置关系有很高的精度要求,其施工安装阶段将给高层建筑本身及周边建筑群体带来复杂的形变影响。为了保障建筑物施工和运营的安全,就必须对其进行沉降观测。本文结合笔者多年的实际工作经验,并结合具体的实例,对高层建筑物沉降原因、沉降观测前的准备工作及沉降观测的实施过程和观测数据的处理方法等进行了论述,最后指出如何通过沉降观测技术准确地反映出高层建筑物的沉降情况。     

基于惯导/天文高精度定姿方法

研究了利用惯性导航系统与天文导航系统进行组合定姿的方法;构造了惯导/天文组合导航系统的状态方程和量测方程;采用卡尔曼滤波技术设计了惯导/天文组合定姿算法。设计飞行器的典型飞行轨迹,通过数学仿真对该算法的有效性进行了验证。结果表明,天文导航能够有效地补偿惯性导航因陀螺漂移带来的误差,非常适用于飞行器的高精度定姿。     

利用GPU实现基于物理模型的流体运动仿真

纳维-斯托克斯方程是描述流体运动的基础物理模型。首先简要介绍了在计算机上实现该模型的数值解算方法。在流体运动的计算机视觉仿真中,密度渲染才是最终结果,因此,又阐述了流体的密度场与速度场的关系,并且给出了流体仿真的基本流程。由于可编程图形处理器(GPU)具有并行性和速度快等特点,流体模拟的解算和渲染在图形处理器上运行更加高效,但是利用GPU编程实现流体仿真必须要实现3个核心转换,最后以支持3维纹理的Direct3D10为例,给出了利用GPU实现流体运动仿真两个简单实例。     

嫦娥一号IIM数据应用处理流程分析

对嫦娥一号干涉成像光谱仪（IIM）数据的特点进行了分析,并就存在的一些问题提出了解决方案,制定了IIM数据应用处理流程,为该数据的正确使用提供方法参考。研究结果表明,在空间域传感器左侧响应偏低,右侧响应偏高;在波谱域长波段响应存在较大偏差。经过绝对定标和辐射畸变校正后的反射率与地基望远镜光谱匹配良好,可以用于应用研究。利用校正后的数据对Aristarchus地区岩石类型开展初步研究的结果表明,该地区在纵向和横向上都存在岩性的多样性。校正后的图像不仅提高了分类精度,还被识别出撞击坑可能存在的滑坡。嫦娥一号IIM能够在全球、区域和局部尺度上以较高的空间分辨率和光谱分辨率获取月表元素和矿物成分信息,有助于深化对月球形成和演化的认识。     

三维城市模型的研究与实践(英文)

The way we interact with spatial data has been changed from 2D map to 3D Virtual Geographic Environment (VGE). Three-dimensional representations of geographic information on a computer are known as VGE, and in particular 3D city models provide an efficient way to integrate massive, heterogenous geospatial information and georeferenced information in urban areas. 3D city modeling (3DCM) is an active research and practice topic in distinct application areas. This paper introduces different modeling paradigms employed in 3D GIS, virtual environment, and AEC/FM. Up-to-date 3DCM technologies are evolving into a data integration and collaborative approach to represent the full spatial coverage of a city, to model both aboveground and underground, outdoor and indoor environments including man-made objects and natural features with 3D geometry, appearance, topology and semantics. Supported by the National Natural Science Foundation of China ( No. 40871212, No. 40671158), the Leading Academic Discipline Project of Shanghai Educational Committee( No.J50104).     

Total electron content processing from GPS observations to facilitate ionospheric modeling

With the increasing global distribution of high rate dual-frequency global positioning system (GPS) receivers, the production of a real-time atmospheric constituent definition, total electron content (TEC), has become a beneficial contributor to the modeling applications used in the assessment of GPS position accuracy and the composition of the ionosphere, plasmasphere, and troposphere. Historically, TEC measurements have been obtained through post processing techniques to produce the quality of data necessary for modeling applications with rigorous error estimate requirements. These procedures necessitated the collection of large volumes of data to address the various abnormalities in the computation of TEC associated with the use of greater data quality controls and source selection while real-time modeling environments must rely on autonomous controls and filtration techniques to prevent the production of erroneous model results. In this paper we present methods for processing TEC in real time, which utilize several procedures including the application of an ionospheric model to automatically perform quality control on the TEC output and the computational techniques used to address receiver multipath, faulty receiver observations, cycle-slips, segmented processing, and receiver calibrations. The resulting TEC measurements are provided with rigorous error estimates validated using the vertical TEC from the Jason satellite mission.

基于CCGIS的三维城市模璎数据生产

立足于生产实际阐述了一种基于CCGIS的三维城市生产工艺,重点说明了三维城市模型数据生产流程和控制,并结合恩施三维信息查询系统为例对该生产工艺进行验证。