手机地图显示尺度划分方法研究

随着移动通信技术的发展,手机地图逐渐成为人们获取位置信息的重要工具。由于手机地图具有屏幕小,快速移动和近距离阅读等特点,所以手机地图内容各要素的分层显示特征更为明显,这要求手机地图显示尺度的划分更加精细。而现有基础电子地图多尺度显示模型无法完全适用于手机地图多尺度显示。为此,针对不同要素视觉感受的差异性,利用眼动实验定量确定了手机地图各要素载负量的权重和计算方法。在此基础上,综合考虑不同要素载负量对显示尺度划分的影响,提出了一种利用主成分迭代分析建立手机地图多尺度显示模型的方法。并与现有基于地图面积载负量建立的地图多尺度显示模型进行了分析比较,为今后手机地图多尺度显示提供科学的参考依据。     

西南印度洋中脊表层沉积物中存在热液组分的地球化学证据

Hydrothermal materials in deep-sea sediments provide a robust tracer to the localized hydrothermal activity at mid-ocean ridges. Major, trace and rare earth element(REE) data for surface sediments collected from the ultraslow spreading Southwest Indian Ridge are presented to examine the existence of hydrothermal component.Biogenic carbonate oozes dominate all the sediment samples, with CaO content varying from 85.5% to 89.9% on a volatile-free basis. The leaching residue of bulk sediments by ~5% HCl is compositionally comparable to the Upper Continental Crust(UCC) in SiO_2, Al_2O_3, CaO, MgO, alkali elements(Rb, Cs) and high field strength elements(Nb, Ta, Zr, Hf, Ti). These detritus-hosted elements are inferred to be prominently derived from the Australian continent by means of eolian dust, while the contribution of local volcaniclastics is insignificant. In addition, the residual fraction shows a clear enrichment in Fe, Mn, and Ba compared with the UCC. Combining the positive Eu anomaly of residual fraction which is opposed to the UCC but the characteristic of hydrothermal fluids and associated precipitates occurred at mid-ocean ridges, the incorporation of localized hydrothermal component can be constrained. REE mixing calculations indicate that more than half REE within the residual fraction(~55%–60%) are derived from a hydrothermal component, which is inferred to be resulted from a diffuse fluid mineralization. The low-temperature diffuse flow may be widely distributed along the slow-ultraslow spreading ridges where crustal faults and fissures abound, and probably have a great mineralization potential.     

悬沙组分对再悬浮过程响应的初步研究——以长江口南槽口门为例

根据2011年5月31日至6月3日在长江口南槽口门附近海域投放三角架观测系统获取的沉积动力观测数据以及现场采集的水样和底质样品,进行底部边界层参数、悬沙粒度及悬沙组分分析,以探讨研究区近底部边界层特征和沉积物再悬浮过程。结果表明,研究区海域的悬沙以粉砂组分为主,潮周期内近底部流速与相应层位的悬沙浓度变化呈正相关,存在显著的再悬浮作用。分析发现,随着水体中悬沙砂组分的增加,再悬浮通量随之显著增加;砂组分减小,则再悬浮通量亦减小。因此,悬沙砂组分是对再悬浮过程响应的敏感组分,在一定程度上可指示和"示踪"再悬浮效应。     

无缝仿射基准转换模型的方差分量估计

以无缝仿射基准变换为例,研究了无缝基准转换模型的方差分量估计理论,导出无缝基准变换过程中两套坐标的方差分量估计公式。通过模拟试验分析表明,采用方差分量估计方法能正确地恢复出客观体现两套坐标误差的方差值,从而有效提高无缝基准转换精度。     

PCA-SIFT 特征匹配算法研究

SIFT特征具有旋转、尺度和明暗变化的不变性,在图像匹配中得到广泛应用。针对SIFT特征匹配中耗时长、匹配点对少、准确率低的问题,提出PCA-SIFT特征匹配的方法。使用更加精简的方法构建特征点描述向量,通过预先构建的投影矩阵对描述向量进行主成分分析,降低描述向量的维度从而提高了特征匹配的速度,同时降维也对描述向量进行了去噪提纯,使得匹配更加准确。实验证明,利用PCA-SIFT特征进行匹配在降低匹配耗时的同时,增加了匹配点对,匹配准确率也得到提高。     

一种利用方差分量估计的BDS卫星定轨算法

针对采用Helmert方差分量估计的方法来调节BDS不同类型卫星之间的权比时,出现的区域站MEO卫星观测值数量少、卡尔曼滤波开始阶段不稳定等问题,提出了一种待滤波稳定后再进行Helmert方差分量估计的改进算法。该算法可以根据卫星类型以及它们的数目,自适应地采取不同的策略。基于BDS观测数据的实验结果表明,采用改进的Helmert方差分量估计方法进行BDS卫星卡尔曼滤波定轨,提高了BDS卫星轨道平均径向精度。     

Image processing and GIS techniques applied to high resolution satellite data for lineament mapping of thermal power plant site in Allahabad district,U.P., India

The present study is based on digital analysis of IRS 1C/1D LISS-III and IRS P6 LISS-IV images for identification of lineaments in Meja Thermal Power Plant site in Allahabad district. In spite of all limitations due to anthropogenic activities of stone quarrying and criss cross unmetalled roads, almost non-existent vegetation indicators and soil moisture, the efforts were made to identify and map a number of lineaments in the study area and these were subsequently verified in the field. Most of the lineaments identified and mapped are not having any major displacement along them or are not displacing or truncating any major rock unit. Field investigations have revealed that there is no drastic change in the trend of rocks along the lineaments mapped in the study area. On the basis of digital analysis of IRS P6 LISS-IV data NE–SW and NW–SE trending lineaments have been identified and mapped. Some NNE–SSW trending lineaments have also been mapped. All the lineaments demarcated in this area still need to be correlated with the seismic data of the area by superimposing the microseismicity data over lineaments.     

Integration of full-waveform LiDAR and hyperspectral data to enhance tea and areca classification

Hyperspectral image and full-waveform light detection and ranging (LiDAR) data provide useful spectral and geometric information for classifying land cover. Hyperspectral images contain a large number of bands, thus providing land-cover discrimination. Waveform LiDAR systems record the entire time-varying intensity of a return signal and supply detailed information on geometric distribution of land cover. This study developed an efficient multi-sensor data fusion approach that integrates hyperspectral data and full-waveform LiDAR information on the basis of minimum noise fraction and principal component analysis. Then, support vector machine was used to classify land cover in mountainous areas. Results showed that using multi-sensor fused data achieved better accuracy than using a hyperspectral image alone, with overall accuracy increasing from 83% to 91% using population error matrices, for the test site. The classification accuracies of forest and tea farms exhibited significant improvement when fused data were used. For example, classification results were more complete and compact in tea farms based on fused data. Fused data considered spectral and geometric land-cover information, and increased the discriminability of vegetation classes that provided similar spectral signatures.     

采用主成分分析法的面状居民地自动选取

居民地选取是一个多种因素相互约束、相互关联的过程,而这些影响居民地重要性因素的关系往往难以定量地描述出来,提出了基于主成分分析法的居民地自动选取方法。首先,采用主成分分析法对这些相互约束、相互影响的因子转换成一组无关变量;其次,对这转换后的无关变量提取主要成分;第三,计算出主成分的权重用以评价居民地的重要性程度;最后,利用开方根模型完成居民地要素的定额选取。该方法将相互关联、相互约束的影响居民地重要性的因子转换成新的无关变量,提炼出其主要成分并计算权值用以综合评价居民地的重要性。实验对比分析表明,该方法综合考虑了居民地要素的行政等级、位置特征和面积大小等因素对居民地重要性的影响,选取结果,较好地保持了居民地选取前后的整体形态,符合选取原则。     

一种高精度的基坑水平位移监测方法探讨

将CPⅢ(高速铁路轨道控制网)平面控制测量的自由测站施测方法应用到基坑水平位移变形监测中,其特点是根据施工现场情况选择任意合适的地点架设测站,避免了施工环境对测量工作的影响和仪器的对中误差。介绍了Helmert方差分量估计定权原理和置平平差原理,通过自编程序完成了基坑变形监测的仿真计算。计算结果证明:利用自由测站采集观测数据,Helmert方差分量估计定权约束平差和置平平差均能够高精度地得到毫米级的基坑变形量,可以应用到基坑水平位移变形监测中。