基于Google Earth的地形图制作技术

介绍一种简单新型地形图制作技术.该技术通过在Goosle Earth中建立多边形,并巧妙地将多边形转化为等高面,记录等高线来实现等高线地形图的制作,并对利用此技术制作地形图的质最进行讨论.该技术在保证一定制图精度的前提下,不但能轻松掌握,而且能缩短制图时间、降低制图成本,具有一定的创新性和推广价值.     

On the attribution of changing pan evaporation in a nature reserve in SW China

Negative trends of measured pan evaporation are widely reported. Studies of the factors that underlie this reduction in pan evaporation have not reached a consensus about the controlling factors. Most studies employ statistical analysis (correlation analysis or stepwise regression) to identify the controlling climatic variables; in contrast, few studies have employed physical‐based theories. In addition, observations of pan evaporation and related climatic variables are reported to be influenced by anthropogenic activities. Consequently, the observed trends of climatic variables in a nature reserve would be useful for understanding regional climate change. The present study site is located in Ailaoshan National Nature Reserve, SW China, which is free of anthropogenic activity. In this study, we firstly applied the adjusted PenPan model to estimate the pan evaporation. Then, using this physical‐based model, we identified a positive trend in pan evaporation, with a much larger increase in the dry season than in the wet season. The model results indicate that the change in the aerodynamic component is larger than that in the radiative component. In contrast to the reduction in wind speed and sunshine hours that has been reported in previous studies at various sites, we found that wind speed and sunshine hours have increased in recent decades, thereby explaining the increase of the pan evaporation rate. Wind speed made the greatest contribution to the change in pan evaporation, followed by sunshine duration. This study indicates that the potential evaporation has increased at this site despite the widely reported reduction in measured pan evaporation. During the dry season, the availability of water for agriculture and agroforestry could be threatened. Copyright © 2012 John Wiley & Sons, Ltd.     

Constitutive model for tailing soils subjected to freeze–thaw cycles based on meso-mechanics and homogenization theory

A constitutive model is proposed for tailing soils subjected to freeze–thaw cycles based on the meso-mechanics and homogenization theory. The evolution of meso-structure upon loading was analyzed within the framework of breakage mechanism. When the new model is formed, tailing soils are idealized as composite materials composed of bonded elements described by an elastic brittle model and frictional elements described by a double hardening model. Based on meso-mechanics and homogenization theory, the nonuniform distributions of stress and strain within the representative volume element are given by introducing a structure parameter of breakage ratio with the derivation of the strain coefficient tensor, which connects the strains of the bonded elements and the representative volume element. The methods for determining model parameters are suggested based on the available tested results. The model proposed here can predict the deformation properties of tailing soils experiencing freeze–thaw cycles with acceptable accuracy. The strain-hardening and post-peak strain-softening behaviors of tailing soils under various confining pressures as well as different numbers of freeze–thaw cycles are well captured, and the dilatancy and contraction features are also adequately represented.

     

面向对象的库区高分一号影像土地利用信息提取

高分一号（GF-1）是我国自主研发的第一颗高分辨率遥感卫星,其包含地物信息较为丰富,已应用于土地利用信息提取,但在水利工程库区土地利用调查方面研究较少。本文以峡江水利枢纽工程库区为例,首先对库区影像进行了基于RPC模型的正射校正、几何精纠正等预处理;然后针对GF-1的传感器响应特性,采用基于多元线性波段拟合的方法对多光谱与全色影像进行融合,该方法相对于传统分量替换法具有更好的融合性能;最后综合利用影像的光谱、纹理及形状等特征,采用面向对象的方法对融合后的库区影像进行了地类信息提取与分类精度评价。试验结果表明,融合影像可以有效提取水利工程库区的土地利用信息,总体分类精度达到87.9%,Kappa系数为0.836,能够满足库区土地利用调查和变化监测的要求。     

基于VB平台桥网间接平差的设计与实现

本文采用间接平差方法,利用VB语言,结合高校教学项目,设计编程了一套基于VB平台的间接平差方法软件,运行解算桥网未知控制点的坐标平差值及高程平差值,并解算其点位精度。结果表明,点位精度不超过3 mm,误差改正数不超过2 mm,解算精度较高,符合要求。由此说明了利用间接平差方法解算桥网的正确性及可行性,并将其运用到高校平差解算其他平面控制网。