Effect of NOAA satellite orbital drift on AVHRR-derived phenological metrics

The U.S. Geological Survey (USGS) Earth Resources Observation and Science (EROS) Center routinely produces and distributes a remote sensing phenology (RSP) dataset derived from the Advanced Very High Resolution Radiometer (AVHRR) 1-km data compiled from a series of National Oceanic and Atmospheric Administration (NOAA) satellites (NOAA-11, −14, −16, −17, −18, and −19). Each NOAA satellite experienced orbital drift during its duty period, which influenced the AVHRR reflectance measurements. To understand the effect of the orbital drift on the AVHRR-derived RSP dataset, we analyzed the impact of solar zenith angle (SZA) on the RSP metrics in the conterminous United States (CONUS). The AVHRR weekly composites were used to calculate the growing-season median SZA at the pixel level for each year from 1989 to 2014. The results showed that the SZA increased towards the end of each NOAA satellite mission with the highest increasing rate occurring during NOAA-11 (1989–1994) and NOAA-14 (1995–2000) missions. The growing-season median SZA values (44°–60°) in 1992, 1993, 1994, 1999, and 2000 were substantially higher than those in other years (28°–40°). The high SZA in those years caused negative trends in the SZA time series, that were statistically significant (at α = 0.05 level) in 76.9% of the CONUS area. A pixel-based temporal correlation analysis showed that the phenological metrics and SZA were significantly correlated (at α = 0.05 level) in 4.1–20.4% of the CONUS area. After excluding the 5 years with high SZA (>40°) from the analysis, the temporal SZA trend was largely reduced, significantly affecting less than 2% of the study area. Additionally, significant correlation between the phenological metrics and SZA was observed in less than 7% of the study area. Our study concluded that the NOAA satellite orbital drift increased SZA, and in turn, influenced the phenological metrics. Elimination of the years with high median SZA reduced the influence of orbital drift on the RSP time series.     

海洋涡旋遥感：进展与挑战

海洋涡旋数量大、分布广、含能高、裹挟强,是研究物质循环、能量级联和圈层耦合的理想载体。对涡旋的全生命周期追踪观测成为21世纪以来海洋遥感领域最重要的进展之一,并引发了新一轮涡旋研究的热潮。本文从涡旋的温度异常、物质示踪、旋转流场和闭合拓扑等特征出发,简述了红外辐射计、可见光扫描仪、微波高度计、合成孔径雷达等遥感技术在涡旋观测中的机理和方法,重点阐述了卫星高度计涡旋识别与追踪算法及其在涡旋形态学、运动学和动力学中的应用。基于虚拟星座下的多参数遥感,介绍了涡旋在海洋、大气、生态等交叉学科领域的前沿应用和最新进展。指出当前涡旋遥感发展面临的亚中尺度、垂直结构、跨学科研究等3大挑战,展望了新一代遥感技术在未来海洋科学特别是涡旋海洋学研究中的应用前景。     

一种多系统组合导航快速选星方法

采用多卫星导航系统组合导航,定位精度和系统可靠性会大幅提升,但导航定位运算量也会成倍增长。为解决多系统组合导航定位精度与实时性之间的矛盾,提出一种新的选星方法。新方法不追求最小GDOP值,而是以满足导航定位精度的GDOP值为前提,结合模糊理论中隶属函数的思想,按卫星在星座中均匀分布为原则进行选星。推导伪距测量的误差模型,分析了GDOP与测量误差之间的关系。北斗、GPS和GLONASS三系统组合导航选星实验结果表明,在不超过3次求解GDOP值的情况下,新方法能以不小于98%的概率得到GDOP≤4。     

Use of cartographic images by expert and novice field geologists in planning fieldwork routes

Topographic maps and aerial photographs are particularly useful when geoscientists are faced with fieldwork tasks such as selecting paths for observation, establishing sampling schemes, or defining field regions. These types of images are crucial in bedrock geologic mapping, a cognitively complex field-based problem-solving task. Geologic mapping requires the geologist to correctly identify rock types and three-dimensional bedrock structures from often partial or poor-quality outcrop data while navigating through unfamiliar terrain. This paper compares the walked routes of novice to expert geologists working in the field (n = 66) with the results of a route planning and navigation survey of a similar population of geologists (n = 77). Results show clearly that those geologists with previous mapping experience make quick and decisive determinations about field areas from available imagery and maps, regardless of whether they are or not physically present in the field area. Recognition of geologic features enabled experts to form and verbalize a specific plan for travel through a landscape based on those features. Novices were less likely to develop specific travel route plans and were less likely to identify critical landscape cues from aerial photographs.     

强跟踪抗差自适应滤波算法及其在无人机导航定位中的应用

针对Sage-Husa自适应滤波算法在无人机导航定位应用中存在滤波发散和定位精度低的问题,本文提出一种强跟踪抗差自适应滤波算法.该算法在Sage-Husa自适应滤波算法基础上,引入强跟踪技术,通过自适应渐消因子降低历史数据对当前滤波的影响,从而抑制滤波发散,增强算法的稳健性;结合量测噪声和系统噪声进行实时估计,并且在估...     

无人机三维倾斜摄影测量助力自然资源调查——以不动产调查为例

随着第一次地理国情普查与监测、第三次全国土地调查等重大自然资源调查类项目的实施,以无人机作为搭载平台的遥感影像获取手段在不断发展并深入应用,特别是无人机航测技术和地理信息技术的结合应用越来越紧密.本文以不动产调查为例,重点论述结合无人机三维倾斜摄影测量技术在内的测绘地理信息新手段的作业原理及应用情况,并对其优缺点进行总...     

重要性权值的驾车导航POI表达规则

在导航电子地图中,针对驾车任务的POI自适应表达是提高导航电子地图信息传输效率的关键。针对这一问题,提出了基于重要性权值的驾车导航POI表达规则。首先,分析了POI重要性权值的影响因素;其次,从影响因素出发,研究了基于权值的POI规则表达的各规则项;最后,设计了POI自适应表达规则库,并在嵌入了数据处理规则库的绘图软件上进行了技术实现。试验结果表明,利用基于权值的POI表达规则进行地图表达,可以提高地图内容的层次性与清晰性,优化驾车导航服务。     

顾及像面畸变的卫星视频稳像

卫星视频每帧影像外方位元素数值存在差别,相邻帧影像间的同名点在像面位置不同,且由于每帧影像均存在几何畸变,经典的帧间的投影变换模型、仿射变换模型等视频稳像的配准模型不能精确描述帧间的同名点关系。针对该问题,本文提出顾及像面畸变的卫星视频稳像算法,基于仿真的卫星视频,验证了该算法的可行性和精度。     

基于激光测高数据的丹江口水库水位变化监测

针对多源星载激光测高数据监测湖泊水位变化问题,该文选取2003—2009年ICESat/GLAH14全球地表高程数据、2018年10月—2019年8月的ICESat-2/ATL13全球内陆水体高程数据,提取丹江口水库多期水位变化数据,最后利用水位站实测水位对其准确度进行了验证,并分析了丹江口水库年度水位变化规律。结果表明,丹江口水库水位呈现明显的季节性变化,每年11月达到较高水位,3月降至较低水位;由ICESat/GLAH14数据估算水库水位的精度为16 cm,ICESat-2/ATL13数据集估算水库水位的精度达到10 cm。因此,ICESat-2/ATL13数据用于内陆水体水位变化监测具有很高的可行性。     

The Austrian node of the natural resources satellite remote sensing cloud service platform:examples of Sino-Austrian cooperation

The Austrian node of the Natural Resources Satellite Remote Sensing Cloud Service Platform was established in 2016 through a cooperation agreement between the Land Satellite Remote Sensing Application Center(LASAC),Ministry of Natural Resources of the Peoples Republic of China and the University of Vienna,Austria.Under this agreement panchromatic and multi-spectral data of the Chinese ZY-3 satellite are pushed to the server at the University of Vienna for use in education and research.So far,nearly 500 GB of data have been uploaded to the server.This technical note briefly introduces the ZY-3 system and illustrates the implementation of the agreement by the first China-Sat Workshop and several case studies.Some of them are already completed,others are still ongoing.They include a geometric accuracy validation of ZY-3 data,an animated visualization of image quick views on a spherical display to demonstrate the time series of the image coverage for Austria and Laos,and the use of ZY-3 data to study the spread of bark beetle in the province of Lower Austria.An accuracy study of DTMs from ZY-3 stereo data,as well as a land cover analysis and comparison of Austria with ZY-3 and other sensors are still ongoing.