Refining the origin of thermal water using stable isotope,hydrochemistry and GIS approaches in Jiaoxi,Taiwan

Comprehending the recharge of thermal springs is crucial for preserving the water quality of such springs. However, limited groundwater well data in mountainous areas presents a challenge to determining thermal-spring recharge areas. This study analyzes the isotopes (δ²H and δ¹⁸O) and major ions in rainwater, streamwater, mountain groundwater and thermal spring water in Jiaoxi, located near Taiwan's largest city, Taipei. The results of the isotope-elevation relationship and GIS recharge analysis indicate that the thermal spring water originated from a remote mountain at elevations of approximately 1170–1480 m, rather than the upstream watershed. The thermal spring water was divided into two groups based on the carbonate saturation index (SI) and isotope composition: the foothill group, which had a positive SI and lower δ value, and the downstream group, which had a negative SI and higher δ value. This study improved the conceptual model of the thermal flow path by demonstrating that the recharge of thermal water is a transboundary regional flow and that the foothill thermal water does not mix with the meteoric water. The revised model also highlights the role of structural lineament trends (faults, fractures and folds) in the movement of regional flow in fractured mountain blocks.     

平面插值法构建DEM时特殊地形的处理

本文根据平面插值法构建DEM的特点,提出了一套处理插值禁域、山脊线、山谷线以及陡坎等特殊地形的方法,以期提高建模与插值的精度。试验证明该方法是行之有效的。     

二维水质扩散模型的建立及应用

根据东湖实际,探讨了二维湖泊水质扩散模型及其定解。提出的二维交替算法,具有快速收敛及确保精度等特点,改进后的内插模型解决了流场和浓度场的初始值和边界条件问题,形成了全湖数字高程模型;在浓度等值线快速生成的基础上,通过接口自动形成信息系统空间和属性文件,完成了专题自动分类。     

基于GPM卫星双频降水雷达的地面降雪识别算法

继搭载在TRMM(Tropical Rainfall Measuring Mission)卫星上的降水雷达PR(Precipitation Radar)之后,GPM(Global Precipitation Measurement)核心观测平台搭载了全球首个双频降水雷达DPR(Dual-Frequency Precipitation Radar),其对降雪的探测能力备受人们关注.本文基于GPM双频降水雷达的探测数据,以三次降水过程(包含降雪、积层混合性降雨和冬季层状云降雨)为例,利用Ku和Ka双波段三个参量(即测量双频比DFR_m垂直廓线斜率、回波顶高、垂直方向上Ku波段最大反射率因子)计算的降雪指数SI(Snow Index)来识别地面降水相态.结果表明,若不使用辅助信息(0℃等温线高度等),利用SI原计算公式能很好地区分夏季降雨和降雪,但较难区分冬季降雨和降雪.为了提高冬季降雨和降雪的分辨效果,改进了反射率因子的质量控制方法,用最小二乘法计算DFR_m垂直廓线的斜率,结果显示改进后地面降雪识别结果与地面自动站观测结果有较好的一致性.     

基于语义认知的地形建模

针对当前地形建模注重渐变地形与地形几何特征(点、线)的表达,缺乏从整体形态上对地形的描述,该文提出将语义信息引入地形建模的方法。从地形建模的认知过程出发,引入"地形语义"描述地形的整体特征,剖析了地形语义的特点,实现了地形语义的形式化表达,设计了语义参与的建模流程,建立原型系统进行了实验。实验表明,地形语义信息作为数据源参与的地形建模能够保留一个地形区域的语义特征,提高了DEM的保真度,该方法进一步拓宽了地形建模数据源,为地形建模及其应用提供了新的思路与方法。     

航天飞机SIR—C数据对内蒙古额济纳旗北部浅层地下水的探测分析

利用航天飞机3号SIR-C数据对额济纳旗北部中-蒙交界处浅层地下水的分布与形成原因进行研究，分析了在SIR-C图像上呈亮条带的机理，研究得出如下结论：（1）浅层地下水区能被ISR-C图像特别是L-HV以及L-HH极化以亮黄色强烈显示，这是与该带地下水位浅，植被长势好，植被固沙形成沙垄等因素造成雷达波体散射以及后向散射强烈所致；（2）在研究区的中-蒙交界段正是地形由缓向陡转折处，这是与拉张正断层原因导致中方上盘相对下降，并在此处具备储水条件有关。（3）雷达遥感能敏感地探测到微地形的变化，可很好地反映地表植被分布和地表及次地表水分，使其在干旱区应用研究具有极大的优势，此研究可能为西部干旱区寻找浅层地下水提供一条快捷，实用的方法。     

利用雷达回波三维拼图资料识别雷暴大风统计研究

应用雷达回波三维组网拼图数据、加密自动站和地面灾害大风资料,对2008—2012年京津冀地区20次区域性雷暴大风天气过程进行了统计。检验了基于模糊逻辑建立的利用回波强度识别大风的算法,分析了大风出现的位置。该大风识别算法确定了雷暴大风的6个雷达识别指标及其对应的权重系数和不同季节的隶属函数。检验分析块状回波、带状回波和片状回波3类大风过程的识别效果,结果表明：块状回波类大风是由孤立的强单体风暴引发的,风暴单体具有回波强、回波顶高、垂直积分液态水含量大和移动快等特点,雷暴大风多出现在风暴单体附近且二者移动路径一致;带状回波的长度远大于宽度,主要包含飑线和弓状回波,大风影响范围广且多位于带状回波的前沿一带;片状回波多指大面积层云回波中镶嵌着强回波单体块的混合回波,对应出现的雷暴大风多位于风暴单体的周边区域。3类回波识别到的可能出现大风区域与实测大风范围基本吻合,块状、带状和片状3种类型的雷暴大风命中率分别为96.2%、68.6%和45.3%,漏报率分别为3.8%、31.4%和54.7%。由于垂直积分液态水含量偏低和回波强度弱,片状雷暴大风识别漏报相对较多;空报原因除了与测站分布稀疏有很大关系外,也与识别算法本身有关。识别检验证明雷暴大风综合识别方法是合理可靠、切实可行的,可以为雷暴大风的短时临近预警业务和系统开发提供技术支撑,这一工作也为进一步预警大风出现的位置提供了基础。     

Vertical accuracy of the SRTM DTED level 1 of Crete

A reference digital elevation model (DEM), produced from contour lines digitization, from topographic maps at scale 1:250.000 is used in order to assess the vertical accuracy of the SRTM DTED level 1 in Crete Island in Southern Greece. The error image interpretation revealed three types of systematic errors: (a) stripping, (b) large voids and (c) those errors resulted from the mis-registration of the Shuttle Radar Topography Mission (SRTM) imagery to the local datum. Terrain was segmented to plane regions and sloping regions. Sloping regions were segmented to aspect regions (aspect being standardized to the eight geographic directions defined in a raster/grid image). Error statistics was computed for the study area as well as the individual terrain classes. Vertical accuracy was found to be terrain class dependent. Sloping regions present greater mean error than the plane ones. Statistical tests verified that the difference in mean error between aspect regions that slope in opposite geographic directions is statistically significant. The greater mean error is observed for SW, W and NW aspect regions. The additional finishing steps applied to the SRTM dataset were not sufficient enough for the systematic errors and the terrain class dependency of the error to be corrected. The observed root-mean-square error (RMSE) for the SRTM DTED-1 of Crete do not fulfil the 16 m RMSE specification for the SRTM mission while the USA national map accuracy standards for the scale 1:250.000 are satisfied.     

数字化内业制图中等高线若干问题的处理

数字化地形图内业等高线的生成过程中,成图软件的不完善和外业高程数据采集的非无限多,将会使生成的等高线变形失真,从而降低图面和测量精度.这种情况并不全是由于外业测量造成的,可由内业完善处理.就等高线的生成修改问题进行了的探讨.     

EGM2008模型在GPS高程转换中的应用研究

分析了EGM2008模型的精度,利用已有GPS水准资料,通过实例对GPS高程转换的多种方案进行比较分析,得出了一些有益的结论和认识。