国家西部测图工程产品模式设计与实践——以1:50000影像地形图为例

为实现国家西部1∶50 000地形图空白区测图工程:丰富产品种类,拓展服务领域的设计宗旨,根据ISO 9000对产品的概念,提出了西部测图工程整体产品模式,并对其进行细化,建立了国家两部测图工程地形图产品模式.本文以西部测图工程1∶50 000影像地形图的设计与实现为实例,详细介绍了1∶50 000影像地形图测绘新产品...     

利用地形正规化校正反立体现象

影像目视判读常会遇到山脊与沟谷的凹凸感与现实相反的反立体现象。消除反立体现象,能有效提高非专业人员对遥感影像的正确使用。立足于反立体现象的成因,本文采用地形正规化模型来校正影像的反立体现象,推导出Lambertian、Cosine-Civco、c校正、b校正这4种地形正规化模型的反立体校正式;对这4种地形正规化模型的反立体校正效果进行了对比,并且与其他5种校正法也进行了对比。通过3个实验区的校正发现,这4种地形正规化模型均能校正反立体现象,但校正影像存在色调偏差;Lambertian、Cosine-Civco的反立体校正影像立体感较强,但影像色调改变较大,视觉效果偏差;c校正、b校正的校正影像在视觉效果和定量指标上都比较接近,基本保持地物光谱信息,校正效果相对较好。从定量指标来看,b校正的反立体校正影像的各指标值整体最小,一定程度代表b校正能取得相对较好的反立体校正效果。与其他方法的对比表明,c校正和b校正的反立体校正不局限于波段个数,在有效消除反立体现象的同时,能相对较好的保留地物光谱信息,有利于影像的定量应用。     

Application of a vanishing, quasi-sigma, vertical coordinate for simulation of high-speed, deep currents over the Sigsbee Escarpment in the Gulf of Mexico

Recent observations over the Sigsbee Escarpment in the Gulf of Mexico have revealed extremely energetic deep currents (near 1 m s⁻¹), which are trapped along the escarpment. Both scientific interest and engineering needs demand dynamical understanding of these extreme events, and can benefit from a numerical model designed to complement observational and theoretical investigations in this region of complicated topography. The primary objective of this study is to develop a modeling methodology capable of simulating these physical processes and apply the model to the Sigsbee Escarpment region. The very steep slope of the Sigsbee Escarpment (0.05–0.1) limits the application of ocean models with traditional terrain-following (sigma) vertical coordinates, which may represent the very complicated topography in the region adequately, can result in large truncation errors during calculation of the horizontal pressure gradient. A new vertical coordinate system, termed a vanishing quasi-sigma coordinate, is implemented in the Navy Coastal Ocean Model for application to the Sigsbee Escarpment region. Vertical coordinate surfaces for this grid have noticeably gentler slopes than a traditional sigma grid, while still following the terrain near the ocean bottom. The new vertical grid is tested with a suite of numerical experiments and compared to a classical sigma-layer model. The numerical error is substantially reduced in the model with the new vertical grid. A one-year, realistic, numerical simulation is performed to simulate strong, deep currents over the Escarpment using a very-high-resolution nested modeling approach. The model results are analyzed to demonstrate that the deep-ocean currents in the simulation replicate the prominent dynamical features of the observed intense currents in the region.     

基于SRTM DEM的InSAR高分辨率山区地表高程重建算法

山体的叠掩和阴影现象造成的信号去相关,一直是InSAR重建山区地表高程的瓶颈之一.为此,提出了一种新的基于粗分辨率SRTM DEM(约90m分辨率)辅助InSAR数据重建山区地表高程的方法.利用SRTM DEM模拟的干涉相位,对ERS-1/2干涉相位做去地形相位处理,得到残余相位.通过对解缠后的残余相位计算方差提取叠掩和阴影区域的噪声,并用平均相位近似恢复噪声区域的相位,然后将其转换为高程,并用SRTM DEM作高程补偿处理,从而实现地表高程重建.最后,定量比较了该方法与传统InSAR技术生成的DEM精度.实验表明,这种方法能有效提高传统InSAR技术生成地表高程的精度,这对提高星载雷达数据的使用效率具有重要意义.     

旋转流体物理实验中见到的大气环流特征

在合适的实验参数下(热力Rossby数R_(OT)=0.1,Taylor数T_a=2.2 ×10~7),在旋转斜压流中,大尺度地形强迫造成低频振荡以及大气环流中的“阻塞”流型。这是由于地形强迫造成的准静止波与行进波的相互作用及共振引起的。地形把波数单一的流动变成多波数的流动。地形强迫使波数减少。     

Two different methods of geoidal height determinations using a spherical harmonic representation of the geopotential, topographic corrections and the height anomaly–geoidal height difference

 It is suggested that a spherical harmonic representation of the geoidal heights using global Earth gravity models (EGM) might be accurate enough for many applications, although we know that some short-wavelength signals are missing in a potential coefficient model. A `direct' method of geoidal height determination from a global Earth gravity model coefficient alone and an `indirect' approach of geoidal height determination through height anomaly computed from a global gravity model are investigated. In both methods, suitable correction terms are applied. The results of computations in two test areas show that the direct and indirect approaches of geoid height determination yield good agreement with the classical gravimetric geoidal heights which are determined from Stokes' formula. Surprisingly, the results of the indirect method of geoidal height determination yield better agreement with the global positioning system (GPS)-levelling derived geoid heights, which are used to demonstrate such improvements, than the results of gravimetric geoid heights at to the same GPS stations. It has been demonstrated that the application of correction terms in both methods improves the agreement of geoidal heights at GPS-levelling stations. It is also found that the correction terms in the direct method of geoidal height determination are mostly similar to the correction terms used for the indirect determination of geoidal heights from height anomalies. Received: 26 July 2001 / Accepted: 21 February 2002     

Topographic and atmospheric corrections of gravimetric geoid determination with special emphasis on the effects of harmonics of degrees zero and one

 The topographic and atmospheric effects of gravimetric geoid determination by the modified Stokes formula, which combines terrestrial gravity and a global geopotential model, are presented. Special emphasis is given to the zero- and first-degree effects. The normal potential is defined in the traditional way, such that the disturbing potential in the exterior of the masses contains no zero- and first-degree harmonics. In contrast, it is shown that, as a result of the topographic masses, the gravimetric geoid includes such harmonics of the order of several centimetres. In addition, the atmosphere contributes with a zero-degree harmonic of magnitude within 1 cm. Received: 5 November 1999 / Accepted: 22 January 2001     

Long internal waves in shear flows: topographic resonance and wave-induced global instability

Issues pertaining to a mechanism whereby long internal waves in shallow seas may give rise to enhanced rates of resuspension of sedimentary material are addressed. The proposed mechanism is intimately related to the creation of conditions in the bottom boundary layer which are favorable for flow separation and spontaneous onset of global instability. It is shown that long waves generated by topographic resonance and propagating upstream against the oncoming current, especially a sheared current, have a strong tendency to release a coherent, pulsating dynamics in their footprint. The passage-through-resonance problem for a sheared, stratified flow is considered, conditions for topographic resonance in the flow model are defined, and preliminary results for the unsteady dynamics in the boundary layer under the footprint of a long wave packet are presented.     

1：5万区域地质图编稿原图的制作

目前,省内各地调单位在编制1∶5万区域地质图编稿原图时采用的方法、程序和依据的技术要求等方面尚不完全一致,直接且不同程度地影响了地质图件的质量。本文就上述问题,依据国家、部颁布的有关规程、规范及局的有关文件精神作了较全面系统的说明与论述,可望今后逐步走上统一标准。     

SCS+C地形辐射校正模型的应用分析研究

在对有森林覆盖的山区影像进行地形辐射校正时，基于太阳-冠层-传感器（SCS）几何关系的校正模型优于基于太阳-地形-传感器（STS）几何关系的模型。SCS校正模型解释了树木不依赖于地形、观测角和光照入射角而具有向地性生长的本质特性，但在某些地形区域，SCS与余弦校正同样存在过度校正的问题。为了解决这个问题，研究者在SCS校正模型中引入C校正系数来解释散射辐射项，提出了SCS+C校正模型。以北京密云Landsat 5影像为数据源，通过目视判别、直方图、定量的统计参数和地物光谱曲线对比等方法，对SCS+C校正模型与传统的余弦校正、C校正和SCS校正模型进行了对比。结果表明，4种方法均能在很大程度上消除地形阴影，更好地反映阴影区域的细节信息； 从总体的光谱特性保真程度来说，余弦和SCS校正都因过度校正问题表现较差，SCS+C校正最好，C校正次之。