基于现场观测资料的卫星海表盐度网格化产品误差分析与质量评估

自欧洲土壤湿度和盐度卫星SMOS和美国宝瓶座盐度卫星Aquarius相继发射之后,多个数据中心发布了两颗卫星的海表盐度网格化产品,其中包括法国海洋研究院SMOS卫星数据小组发布SMOS Locean L3盐度产品、西班牙巴塞罗那专家中心发布SMOS BEC L4盐度产品和美国宇航局喷气动力实验室发布AquariusV3.0 CAP L3盐度产品。本文利用精确盐度现场观测资料从产品精度和模拟海洋现象能力两个方面对以上3种产品质量进行了评估。研究表明:(1) 在精度方面,与盐度现场资料相比,Aquarius CAP 产品质量最高,产品盐度偏差和均方根误差全年稳定且偏差较小,部分海域达到了设计精度;SMOS两种卫星产品在全球海域偏差较不稳定,个别月份出现异常偏差值;SMOS产品在低纬和开阔海域的数据质量相对较高,但在高纬海域仍存在较大误差,需要进一步提升;(2) 在刻画海洋现象方面,Aquarius产品在热带太平洋较好刻画了淡池东缘盐度锋,SMOS BEC产品的刻画能力次之,SMOS Locean产品在热带太平洋充满了小尺度噪音,描述物理现象方面表现偏差。     

高分辨率天绘卫星数据遥感地质应用研究

天绘卫星是我国新发射的卫星,有蓝色、红色、绿色、近红外4个波段,空间分辨率为10m,可以完成遥感地质应用。笔者选择新疆雪米斯坦火山岩带西段作为研究区,利用天绘卫星数据进行了地质研究,包括各类火山岩层的识别和划分、断层识别、含铁蚀变矿物的提取等,并进行了野外地质验证。研究表明,天绘卫星遥感数据能够很好识别出多种火山岩成矿要素,在地质找矿领域具有很好的应用潜力。     

On Measurements of the Tide at Churchill,Hudson Bay

Since the late 1990s the semi-diurnal tide at Churchill, on the western shore of Hudson Bay, has been decreasing in amplitude, with M₂ amplitudes falling from approximately 154?cm in 1998 to 146?cm in 2012 and 142?cm in 2014. There has been a corresponding small increase in phase lag. Mean low water, decreasing throughout most of the twentieth century, has levelled off. Although the tidal changes could reflect merely a malfunctioning tide gauge, the fact that there are no other measurements in the region and the possibility that the tide is revealing important environmental changes calls for serious investigation. Satellite altimeter measurements of the tide in Hudson Bay are complicated by the seasonal ice cover; at most locations less than 40% of satellite passes return valid ocean heights and even those can be impacted by errors from sea ice. Because the combined TOPEX/Poseidon, Jason-1, and Jason-2 time series is more than 23 years long, it is now possible to obtain sufficient data at crossover locations near Churchill to search for tidal changes. The satellites sense no changes in M₂ that are comparable to the changes seen at the Churchill gauge. The changes appear to be localized to the harbour, or to the Churchill River, or to the gauge itself.     

基于在线加权式多模型方法的磁控立方星姿态机动控制

针对一类低轨道磁控立方星,提出一种在线加权式多模型自适应跟踪控制方法,使得卫星姿态能够根据指令实现较大角度的机动,并将误差保持在容许的范围内,达到满意的动态性能.首先,在卫星的几个姿态平衡点处建立控制系统模型,通过模型匹配度指标值,在线调整加权式多模型控制算法;其次,在多模型控制回路中引入动态自适应神经网络,充分利用其结构和参数均可以在线自适应调节的特点,以消除卫星在轨运行时受到的地球磁场变化的影响,并抑制不确定的外部干扰,提高系统鲁棒性能;最后,以某立方星为对象,进行仿真验证,结果表明所提方法是有效的.     

A comparative study of the segmentation of weighted aggregation and multiresolution segmentation

Multiresolution segmentation (MRS) algorithm has been widely used to handle very-high-resolution (VHR) remote sensing images in the past decades. Unfortunately, segmentation quality is limited by the dependency of parameter selection on users’ experience and diverse images. Contrarily, the segmentation by weighted aggregation (SWA) can partly overcome the above limitations and produce an optimal segmentation for maximizing the homogeneity within segments and the heterogeneity across segments. However, SWA is solely tested and justified with digital photos in computer vision field instead of VHR images. This study aims at evaluating SWA performance on VHR imagery. First, multiscale spectral, shape, and texture features are defined to measure homogeneity of image objects for segmentation. Second, SWA is implemented to handle QuickBird, unmanned aerial vehicle (UAV), and GF-1 VHR images and further compared with MRS in eCognition software to demonstrate the applicability of SWA to diverse images in building, vegetation and water, forest stands, farmland, and mountain areas. Third, the results are fully evaluated with quantitative measurements on segmented objects and classification-based accuracy assessment on geographic information system vector data. The results indicate that SWA can produce higher quality segmentations, need fewer parameters and manual interventions, create fewer segmentation levels, incorporate more features, and obtain larger classification accuracy than MRS.     

基于资源三号卫星影像的数字正射影像快速生产及精度分析

资源三号卫星的成功发射填补了我国立体卫星测绘的空白,且可提供高分辨率的遥感影像。本文基于资源三号卫星影像,简要介绍了数字正射影像(DOM)快速制作流程,并分别对比分析其在无控、有控以及稀少控制条件下的精度。     

基于资源三号卫星遥感影像局部控制纠正精度分析

资源三号测绘卫星是我国第一颗民用高分辨率三线阵立体的测绘卫星,近年来,农业、灾害、资源环境、公共安全等部门对基于资源三号卫星影像的测绘地理信息服务需求量明显增大。本文通过具体研究试验,利用不同数量平面控制点对分辨率为2 m的资源三号卫星影像进行局部控制纠正,并对纠正后所产生的误差进行对比分析,所得的实验结果对资源三号卫星影像的生产具有一定的指导意义。     

基于多光谱影像和DEM的泥石流堆积扇识别研究——以白龙江流域武都段为例

选取中国泥石流多发区白龙江流域武都段作为研究区,在对该区域泥石流堆积扇的形态特征和堆积范围进行实地调绘的基础上,利用高分辨率影像(SPOT)进行目视解译,获得研究区部分泥石流堆积扇和非泥石流堆积区的分布范围,将其作为已知样本区。利用该区域多光谱遥感影像(ASTER)和数字高程模型(DEM),提取包含波段比和主分量的几十种特征指标。通过运用方差分析和聚类分析等方法对各指标进行分析计算,选取对区别泥石流堆积扇最具显著意义的指标进行输入,进而采用基于像元的分类方法识别泥石流堆积扇。得到如下结论:SPOT与ASTER融合影像的波段比、主分量指标可以有效地突出土壤岩石中的矿物成分,对泥石流堆积扇的识别具有显著意义;利用筛选出的遥感指标和地形指标作为输入,进行监督分类识别泥石流堆积扇,能够有效地将遥感指标和地形指标相结合,提取的堆积扇覆盖范围与实际情况较为接近。     

基于像素工厂的地理国情普查标准时点核准DOM生产关键技术研究

针对第一次全国地理国情普查标准时点核准对影像数据的需求,本文对利用像素工厂软件进行正射影像制作的关键技术进行了研究,总结像素工厂软件的优势,为卫星影像数据制作数字正射影像提供指导。     

Horizontal accuracy assessment of very high resolution Google Earth images in the city of Rome,Italy

Google Earth (GE) has recently become the focus of increasing interest and popularity among available online virtual globes used in scientific research projects, due to the free and easily accessed satellite imagery provided with global coverage. Nevertheless, the uses of this service raises several research questions on the quality and uncertainty of spatial data (e.g. positional accuracy, precision, consistency), with implications for potential uses like data collection and validation. This paper aims to analyze the horizontal accuracy of very high resolution (VHR) GE images in the city of Rome (Italy) for the years 2007, 2011, and 2013. The evaluation was conducted by using both Global Positioning System ground truth data and cadastral photogrammetric vertex as independent check points. The validation process includes the comparison of histograms, graph plots, tests of normality, azimuthal direction errors, and the calculation of standard statistical parameters. The results show that GE VHR imageries of Rome have an overall positional accuracy close to 1 m, sufficient for deriving ground truth samples, measurements, and large-scale planimetric maps.