A GIS-based study toward forecast of suburban forest change

At a time when the concept of ‘human and environmental symbiosis’ has taken on much significance, protection of suburban forests (i.e. forests adjacent to or near developed areas) is a topic that has drawn much attention. Suburban forests have, since ancient times, been places where people have gathered firewood and cultured trees. As a result, the vegetation of suburban forests is only partially natural and continues to change as the forms of human activity in and around them changes. Accurate forecasts of how suburban forests will change are, therefore, an important element in the debate over how to protect them. In this study, a suburban forest was analyzed with laser radar sensing, multi-spectrum scanning, digital photogrammetry analysis, aerial photograph interpretation, and a field survey. Data gathered using these techniques were compiled on a GIS to forecast future changes in the forest. Aerial photographs taken over the past 50 years were analyzed to illuminate changes in the forest over that period. Specifically, comparisons of precise Digital Elevation Models (DEMs) measured by using digital photogrammetry workstations made it possible to estimate growth in forest height. The possible future conversion of such results to estimates of amounts of carbon dioxide consolidated by forests should be very significant for discussions of global environmental problems. This revised version was published online in July 2006 with corrections to the Cover Date.     

Superosculating intermediate orbits: Fourth-and fifth-order tangencies to trajectories of perturbed motion

The theory of superosculating intermediate orbits previously suggested by the author is developed. A new class of orbits with a fourth-order tangency to the actual trajectory of a celestial body at the initial time is constructed. Orbits with a fifth-order tangency have been constructed for the first time. The motion in the constructed orbits is represented as a combination of two motions: the motion of a fictitious attracting center with a variable mass and the motion relative to this center. The first motion is generally parabolic, while the second motion is described by the equations of the Gylden—Mestschersky problem. The variation in the mass of the fictitious center obeys Mestschersky’s first and combined laws. The new orbits represent more accurately the actual motion in the initial segment of the trajectory than an osculating Keplerian orbit and other existing analogues. Encke’s generalized methods of special perturbations in which the constructed intermediate orbits are used as reference orbits are presented. Numerical simulations using the approximations of the motions of Asteroid Toutatis and Comet P/Honda—Mrkos—Pajdu?áková as examples confirm that the constructed orbits are highly efficient. Their application is particularly beneficial in investigating strongly perturbed motion.     

利用地面控制点进行卫星摄影三线阵CCD相机的动态检测

卫星发射及在轨飞行中,环境变化会影响三线阵CCD相机的内方位元素。实际上使相机成为不符合摄影测量定义的相机,导致由经典摄影测量原理推导的有关公式应用受到影响。因此,将变化了的内方位元素规范为正视相机的x坐标为零的内方位元素系统,而此系统的其他参数则作为EFP法反解内方位元素的待求参数,并给出了计算数学模型及模拟计算结果。     

非保守弹性基础板的拟固有频率变分原理

对受随从力作用的非保守弹性基础矩形薄板，针对由微分－积分方程构成的基本方程和边界条件，建立了以挠度和基础反力为两变量的拟固有频率的广义变分原理，从而为该类问题的近似求解提供了理论基础。     

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数字摄影测量下的虚拟城市建设

主要探讨数字城市基础地理信息的内容及获取途径,以及数字摄影测量在虚拟城市建设中的应用,探索了建立虚拟城市的方法。     

基于ArcGIS与航空影像的城市三维建模方法研究

针对当前＂数字城市＂建设对三维建筑模型的需求,提出了一种基于Arc GIS平台,利用航空影像及其4D产品进行城市快速三维建模的方法,详细介绍了建模数据来源、三维模型构建方法及技术路线等,并进行了试验及分析,验证了该方法的可行性和高效性。     

数字航空摄影测量数据处理关键技术探讨

随着计算机技术、测绘技术与信息技术的快速发展,航空摄影测量技术也取得了前所未有的进步,数字航空摄影测量技术已经成为现代航空摄影测量的主要方式。因此,对数字航空摄影测量进行研究,具有十分重要的现实意义。本文首先介绍了数字航空摄影测量的发展与应用领域,然后分析了数字航空摄影测量数据处理关键技术及其技术难点,最后对本课题的研究进行了总结。     

无人机载双拼相机低空航测系统技术研究

目前国内大多数无人机航测系统所采用的单相机平面精度可达到要求,但高程精度无法满足大比例尺测图要求。本文主要介绍一种无人机载双拼组合宽角相机低空航测系统,其组成结构、双拼组合宽角数码相机原理、数据处理软件,以及利用该系统进行大比例尺测图的生产流程。它与单相机系统的最大不同点是,通过双拼组合扩大了成像系统的旁向视场角,使得在等同航高条件下,航带影像地面覆盖宽度增加一倍,从而达到提高效率的目的。