时间序列InSAR监测地表形变

针对相干点目标的时间序列,提出了地表形变InSAR技术监测方法,该方法适用于小数据集分析。并采用郑州地区2007年1月到2010年4月期间的8景ALOS PALSAR数据进行验证分析。研究表明,识别的相干点目标具有大的干涉相干值和小的振幅离差,在时间序列中具有可靠的相位。从误差分析和与ENVISAT PSInSAR结果对比分析表明,该文求得的形变速率标准差在0.34mm/a和5.56mm/a之间,表明提出方法是可靠的。     

Atmospheric constituent inversion problems: Implications for baseline monitoring

The importance of ill-posed inverse problems in atmospheric chemistry is reviewed. Most models for the determination of sources and sinks of atmospheric constitutents lead to such ill-posed inverse problems. Consequently, source determinations may be subject to severe amplification of observational error, particularly in the most rapidly varying components. Therefore, mathematical analysis of the various inverse problems needs to be undertaken in order to determine the extent to which a given set of data contains usable information about source/sink processes.Centre for Mathematical Analysis, Australian National University     

Evaluating the Effects of Autofluorescence during Raman Hyperspectral Imaging

Raman hyperspectral imaging is becoming a popular technique to analyse geological materials. Autofluorescence can affect the quality of the spectra that comprise hyperspectral data sets. Few studies have addressed potential misinterpretation of Raman images from hyperspectral data sets affected by autofluorescence. Additionally, little work has been done to develop methods for identifying the spatial distribution of spectra affected by autofluorescence. This study illustrates how autofluorescence may lead to misinterpretation of the distribution of materials based on intensity at a point images. A method is proposed utilising signal to axis analysis to create images that identify regions affected by autofluorescence. Post‐processing baseline correction is often used to address autofluorescence, and most software programs utilise a form of partial least squares regression modelling based on a subjective choice of polynomial order. This study shows that an inappropriate choice of polynomial order can introduce error, which may lead to misinterpretation of Raman images. A signal to axis analysis method is proposed to statistically compare seemingly ‘appropriate’ baseline correction trials. Although post‐processing of hyperspectral data sets and creating Raman images seem simple, data quality issues such as autofluorescence must be considered. If baseline correction is deemed necessary, it should be addressed as an experiment involving statistical comparison.     

Historical abundance of juvenile commercial fish in coastal habitats: Implications for fish habitat management in Canada

An important component of science-based fisheries policy is the provision of habitat adequate for population renewal. In Canada, the Fisheries Act pays little attention to managing fish habitat, and was further weakened by changes enacted in 2012. Specifically, determining the role of fish habitat in contributing to fisheries and fish stock recovery is challenging when many stocks have severely declined and no longer occupy former habitats. This study compared the abundance of juvenile fish in coastal vegetated habitats before and after collapse or decline of groundfish stocks in Atlantic Canada. This comparison was done by compiling past studies that surveyed juvenile Atlantic cod (Gadus morhua) and pollock (Pollachius virens) in vegetated habitats across three provinces. Two studies were repeated, and one that already had post-collapse data was analyzed to quantify long-term changes in juvenile abundance. In all three cases substantial reduction in juvenile abundance coincided with declines in adult stocks. However, juvenile fish still occur in coastal habitats and could aid in adult stock recovery. The current version of the Canadian Fisheries Act requires presence of an ongoing fishery to trigger habitat protection. This is problematic as low fish abundance may lead to lowered habitat protection and potentially habitat degradation, with less or lesser-quality habitat for fish in the future. Thus, recommendations are made to repeal the 2012 Fisheries Act changes and enhance current fish habitat legislation. Using a precautionary approach for coastal fish habitat management, particularly in valuing its potential for fish stock recovery, would strengthen Canadian fisheries management.     

BDS/GPS/GLONASS组合单历元姿态测量性能对比分析

相比于单一卫星导航系统,多卫星导航系统组合具有显著增加可用卫星数目、改善卫星空间几何结构等优点,因而多卫星导航系统组合应用成为近年来关注的热点。在复杂观测条件下,利用BDS/GPS/GLONASS组合进行载体姿态测量具有单系统无法比拟的优势。首先阐述了BDS/GPS/GLONASS组合超短基线解算的双差模型以及姿态测量基本原理;然后分析了BDS/GPS/GLONASS组合多频单历元姿态测量性能。通过实测静态数据设置不同高度截止角进行分析表明:相比于单系统及双系统组合的姿态测量,BDS/GPS/GLONASS组合能够有效地提高姿态测量的精度、稳定性和可用性。当运动载体处于高楼、峡谷等受遮挡严重的复杂环境时,BDS/GPS/GLONASS组合单历元姿态测量更具有应用价值。     

BDS/GPS组合单历元基线解算方法

阐述了BDS/GPS单历元解算函数模型的相关理论,并进行了相应的公式推导。在此基础上,利用基于正则化的载波相位解算模型,解算宽巷模糊度。首先将BDS卫星宽巷模糊度值作为约束固定出IGSO和MEO卫星的模糊度;然后再将IGSO和MEO卫星模糊度值作为约束来固定GEO卫星模糊度。通过实测数据对该方法进行测试和分析,结果表明:BDS/GPS组合系统单历元宽巷模糊度成功率为100%;基频模糊度成功率90%以上;N、E、U方向定位精度达到了毫米至厘米级。     

基于 K-Medoid 聚类算法的 GPS 坐标转换研究

对GPS网约束平差时,GPS控制网的精度与坐标系统转换控制点的位置选择有关。通过实验分析得出,整个网的检核点与相应的转换控制点总距离越远,坐标转换后网的精度越低。在此基础上,提出使用K-Medoid聚类算法,通过计算机程序自动寻找用于计算坐标系统转换参数的最佳控制点,并将文中方法运用于某大桥GPS控制网的控制点选取,通过工程实例验证了基于K-Medoid聚类方法的GPS坐标系统转换的可行性。     

陆态网测站高精度解算分区方案

中国大陆构造环境监测网络由260个连续全球定位系统观测站点和2 000个不定期全球定位系统观测站点构成,一般采用GAMIT或Bernese高精度数据处理软件进行处理。由于GAMIT及Bernese软件对测站数处理能力的限制,必须对陆态网连续运行基准站进行分区解算。针对这一问题,为研究不同分区方案对陆态网解算精度的影响,该文基于全国55个陆态网络连续运行基准站数据,采用整网解算方案以及间距分区法和区域子网划分法分别进行解算,并以整网解算结果作为标准值,对比两种分区方案与整网解算方案的基线长度差及坐标差。结果表明,间距分区方案解算精度比区域子网划分方案精度高,可实现对陆态网分区的高精度解算。最后利用间距分区法对全国240个陆态网络连续运行基准站进行分区解算,得到了较高精度的解算结果。     

无人机航测水域控制点布设方案的精度试验

针对大面积水域航测控制点布设困难,成果精度难以保障的问题,该文重点研究了在其周边区域布设控制点的方法,提出采用密周边隔基线的区域网控制点布设方法,逐步增加控制点布设间距,减少控制点数量,优化区域网控制点布设方案。相比于传统航测区域网控制点布设方法,其需要的外业控制点则更少,而达到的成果精度相当,提高了经济效益。试验显示,控制点采用"密周边2~12条基线间距布设"可满足测制1∶500大比例尺地形图精度的要求。     

三种软件解算GPS长基线的精度分析

探讨利用LGO、TGO和Pinnacle三种GPS数据处理商业软件解算长基线的方法。通过实例计算,与GPS数据处理软件GAMIT解算结果进行对比分析,再利用不同解算方式和不同改正模型对基线解算精度进行比较,验证了LGO、TGO和Pinnacle能够在不同长度的基线范围内解算出高精度的成果。根据工程的精度要求,可以选用不同商业软件进行数据处理,对GPS数据处理方法进行了有益的探索。