基于自适应阈值的船舶轨迹异常点检测算法

定位技术的快速发展催生了轨迹大数据,轨迹数据中总是存在着明显偏离轨迹的异常点。检测出轨迹中的异常点对提高数据质量和后续知识发现精度至关重要。目前轨迹异常点检测算法主要为恒定速度阈值法,没有考虑目标在不同时刻运动状态的变化,仅能检测出速度超出指定阈值的一部分异常点,甚至出现检测错误的情况,算法鲁棒性较差。针对现有问题,本文提出一种基于自适应阈值的轨迹异常点检测算法（Trajectory Outlier Detection Algorithm based on adaptive Threshold, TODAT）。TODAT算法充分考虑了目标在一段时间内的运动信息和观测噪声的影响,采用局部阈值窗和均值滤波窗来计算阈值和速度,同时又引入了经济航速阈值和连续异常点放回机制。基于真实船舶数据的实验结果表明,本文算法可根据轨迹数据得到自适应的阈值,有效检测出全部异常点,大幅度提高轨迹数据的质量。     

基于微波辐射计的海面溢油监测研究

控制海面溢油对于保护环境和减少经济损失是非常重要的,监测海面溢油是遥感技术的一个重要应用方面。利用美国对地观测系统卫星EOS的AMSR\|E微波辐射计探测资料,结合阈值梯度算法和基于R-L分数阶微分梯度算子边缘提取算法,提出了基于微波辐射计的海面溢油监测算法,并以2010年发生在墨西哥湾的漏油事件为例,进行了溢油范围反演研究,得到了较好的实验验证结果。     

基于多源数据的阿勒泰地区雪深反演研究

利用阿勒泰地区 2010~2012年冬季(11月~次年2月)3类积雪数据:风云三号微波成像仪(FY\|3/MWRI)反演的雪深数据、美国人机交互式多仪器冰雪制图系统(IMS)积雪面积数据、阿勒泰及周边地区实测雪深数据,进行积雪深度的反演研究。通过结合3类积雪数据的各自优势,建立修正模型,最终得到较准确的研究区雪深数据。同时通过编程实现了相应模型的操作平台,为今后研究区积雪业务化监测做好准备。结果表明:模型提高了FY\|3/MWRI数据反演阿勒泰地区积雪深度的准确性,改善了FY\|3/MWRI数据在阿勒泰地区雪深反演偏低的缺点,使微波与实测平均雪深误差由修正前的21.7~12.1 cm缩小为修正后的3.7~1.5 cm。     

基于多源干旱指数的黄淮海平原干旱监测

黄淮海平原是我国重要的粮食基地,由于季风、气候等的影响,干旱频发,严重影响了粮食生产,实时监测黄淮海平原的干旱情况,对于合理制定农业政策、指导农业生产具有重要意义。基于MODIS反射率产品、温度产品和气象站点降雨数据等,采用改进归一化水指数(MNDWI)、植被健康指数(VHI)和标准化降水指数(SPI),对黄淮海平原2001~2012年干旱情况进行监测,分析其空间、季节、年际变化规律及其潜在原因,并根据结果确定3个指数的使用条件。结果发现:黄淮海平原燕山山麓和太行山山麓受西伯利亚冬季风的影响,同时由于春天植被覆盖少,水份蒸发较快,易发生春旱;农作物区在海拔25~100m之间比其他地区要干旱;12年间2003年干旱最弱。所采用遥感指数由于对水分温度敏感适用于实时监测,而气象指数SPI适用于长时间序列的干旱变化监测,亦可用于干旱预测。     

面向亚像元级积雪信息提取的MODIS影像波段融合方法研究

MODIS影像因其共享性和时间序列的完整性而成为大区域积雪监测研究广泛使用的数据源,进行MODIS影像波段间融合,能够为积雪研究提供较高分辨率的影像数据源。为了充分利用MODIS影像250 m分辨率波段的空间和光谱信息,提取亚像元级的积雪面积,使用两种具有高光谱保真度的影像融合方法：基于SFIM变换和基于小波变换的融合方法,采取不同的波段组合策略,对MODIS影像bands 1~2和bands 3~7进行融合,并以Landsat TM影像的积雪分类图作为“真值”,对融合后影像进行混合像元分解得到的积雪丰度图的精度进行评价。结果表明：利用基于SFIM变换和小波变换方法融合后影像提取的积雪分类图精度较高,数量精度为75%,比未融合影像积雪分类图的精度提高了6%,表明MODIS影像波段融合是一种提取高精度积雪信息的有效方法。     

Monitoring by Remote Sensing of Habitat Quality Changes in Xianyang City

With the accelerating process of society，economy and urbanization，land use and landscape changes have gradually become important to make effects on regional habitat quality.It is necessary to further investigate those two effects，the result of which can provide a scientific basis for regional habitat conservation and reasonable utilization of land，then will be of great importance in habitat protection and development of the region.In this paper，the study area was located in Xianyang city，Shaanxi Province，which had the frequent human activities and obvious land use changes.Based on the classification of land use data which interpreted by remote sensing，supported by ArcGIS software，the land use transfer matrix of Xianyang from 2000 to 2010 was analyzed.Landscape metrics were calculated by the Fragstats software，which represented for the landscape pattern changes and spatial characteristics.The InVEST model was selected to evaluate habitat quality in study area.The habitat quality changes was monitored.The results indicate that the integrated land use dynamics of Xianyang city is 2.34%，and the changes of land use rate is slow.The main transition from cultivated land and grassland to forest and construction land，which cause the area of first two land use types reduced，and the latter two types increased.The degree of fragmentation and the complexity of structure in landscape are higher than before.Habitat quality improved slightly，and its overall spatial pattern is that central and north areas are relatively higher than the south.Area percentage of excellent，good and poor grades increase，while the habitat quality of medium grade significantly decline.Among 14 districts and counties of habitat quality in Xianyang city，Xunyi County is the best，and the improved magnitude of Liquan county is the most significant.The main driving force of habitat quality change is the transform of land use pattern.Therefore，the relevant departments of Xianyang city should continue to implement the ecological protection measures，and increase the intensity about the protection and management of environment.Thereby to promote the coordinated sustainable development of land use and habitats.     

The Comparison of Reflectance based on Different Terrain Correction

Selecting the Xinglong Mountain which locates in the southeast of Lanzhou city，GanSu province as an example.Using the Landsat8 satellite image as the data source，the Cosine method，C and the modified Minnaert methods were used for each band in the study area.Comparing with the results of the field measurement reflectance and the statistical characteristics of image，the result showed that the cosine method has a perfect correction in the visible and short wave infrared wavelength，the C correction has a serious over\|correct，however.In the Near Infrared Wavelength，the better result obtained by C correction，and the cosine method has over\|correct otherwise.Comparing with the correct effect of whole bands，the modified Minnaert method has an ideal correct effect.The comparison of before and after correction we found that there is a smaller difference for three methods in the smaller slope，and the over correct is mostly in the south.What’s more，with the increase of the slope，the over correct is more obviously，but，there is a little over correct which used the modified Minnaert method in the whole area，it’s more suitable in large slope and the complicated area.     

LM以及CIA效应对TanSat 3个波段吸收光谱的影响

分析了Line Mixing(LM)以及Collision\|Induced Absorption(CIA)效应对中国全球二氧化碳监测科学实验卫星(TanSat)反演CO2所用的CO2的1.61、2.06 μm以及O2 0.76 μm 3个波段气体吸收的影响。LM效应对CO2的1.61、2.06 μm气体吸收截面的影响约2%,LM以及CIA效应对O2 0.76 μm波段的影响,在翼部达到75%,在中心区域约2%。LM效应使谱线线型变窄,使谱线中心吸收波数处吸收截面增大,翼部区域吸收截面减小。考虑LM以及CIA效应后,减小采用传统Voigt线型计算截面存在的结构性误差。分析了气体吸收截面以及LM效应随温度、气压的变化情况,LM效应在压强较大以及温度较低时对吸收截面影响较大。最后,在3个波段选择合理的气压、温度以及波数间隔,建立三维吸收截面查找表,在满足计算精度的同时节约时间,满足卫星大量观测反演的需要。