基于MODIS的青藏高原雪线高度遥感监测

雪线作为区分积雪覆盖区与无雪区的边界线,是冰冻圈各要素中对气候变化最为敏感的指示器。利用去云后的MODIS积雪面积比例产品并结合DEM数据,通过雪线像元及其高度的提取、雪线高度场的建立,对青藏高原近12a(2000~2011年)雪线高度的时空变化特征进行了分析。结果表明:青藏高原雪线高度的分布受地形的影响,高原内部的雪线高度明显高于周围山区;在近12a中,青藏高原的雪线高度变化虽然没有明显的年际变化趋势(升高或者降低),但是体现出较高的年内和年际波动特征,特别是青藏高原的东部和南部地区由于受西南季风的影响,夏季雪线高度的年际变化尤为强烈。提出基于MODIS的雪线高度提取方法具有较好的应用潜力,能够适用于其他地方雪线高度的遥感监测。     

基于CryoSat-2雷达高度计青藏高原地区冰川高度变化提取方法对比

基于2010~2016年CryoSat-2雷达高度计SARIn模式的Level 2测高数据,结合青藏高原地区冰川矢量数据以及全球GEDM数据,通过重叠脚印法、伪平面拟合法以及较新的曲面拟合法提取青藏高原地区典型冰川冰帽的高度变化值。结果表明：①CryoSat-2测高数据应用该3种方法提取山地冰川高度变化具备可行性;②提取高度变化的3种方法各有优劣,以此提供了提取山地冰川高度变化的方法选择的依据;③应用上述3种方法获取的青藏高原地区典型冰川冰帽2010~2016年的定量高度变化结果,绝大多数的冰川都处于消融状态且3种方法提取的高度变化结果增、减趋势一致。处于西昆仑山脉的中峰冰川、古里雅、土则岗目冰川缩减速率较慢,而帕米尔高原的慕士塔格冰川缩减略快,两者的缩减速度都趋于平缓。处于念青唐古拉山脉的来古、恰青冰川高度变化速率最大。     

基于CryoSat-2雷达高度计青藏高原地区冰川高度变化提取方法对比

基于2010~2016年CryoSat-2雷达高度计SARIn模式的Level 2测高数据，结合青藏高原地区冰川矢量数据以及全球GEDM数据，通过重叠脚印法、伪平面拟合法以及较新的曲面拟合法提取青藏高原地区典型冰川冰帽的高度变化值。结果表明：①CryoSat-2测高数据应用该3种方法提取山地冰川高度变化具备可行性;②提取高度变化的3种方法各有优劣，以此提供了提取山地冰川高度变化的方法选择的依据;③应用上述3种方法获取的青藏高原地区典型冰川冰帽2010~2016年的定量高度变化结果，绝大多数的冰川都处于消融状态且3种方法提取的高度变化结果增、减趋势一致。处于西昆仑山脉的中峰冰川、古里雅、土则岗目冰川缩减速率较慢，而帕米尔高原的慕士塔格冰川缩减略快，两者的缩减速度都趋于平缓。处于念青唐古拉山脉的来古、恰青冰川高度变化速率最大。     

卫星图像色差非线性增强用于冰川解译

卫星图像对自然环境复杂,难以考察或需长期连续观测的冰川作用区,提供了宝贵的冰川信息。我国冰川编目已部分采用卫片解译结果,加快了工作的进程。由于冰雪光谱组成的特征,在单波段片及假彩色合成片上所能提供的冰川信息,仅限于冰川作用的界限、面积、型态类型及雪线位置等要素。本文在分析各类冰面状态所占灰阶范围的基础上,用拷贝来调节反差,非线性地扩展了冰雪间的灰阶,使各类冰面在     

天体高度观测App设计与实现

舰船的卫星和无线电导航系统很容易因受到敌方攻击或干扰而失能失效。天文航海定位方法因具有独立自主、不受电磁干扰等优点,可以发挥重要保底作用。针对传统六分仪观测天体高度定位存在依赖水天线、高度值修正需要手工查算表册、过程繁杂、容易出错等缺点,开发了一种基于Android平台的天体高度观测App。测高原理的实质是以重力加速度方向为垂直基准,测量加速度传感器的输出量换算为角度。App嵌入了PyEphem星历库,可以对天体高度观测值自动修正。天体高度观测精度基本满足天文定位要求,该App未来还有进一步提高精度、增加定位功能的潜力。     

改进十字链表的存储方法在短路电流计算中的应用

节点导纳矩阵是一个稀疏矩阵,短路电流计算需要对导纳矩阵数据进行查询。为了既能保持快速按行列查询元素数值,又进一步提高按数值查询其所在行列的效率,以便于存储调用及后续矩阵的处理,提出构建高度平衡二叉树的改进十字链表方法,即在十字链表存储的基础上,拓展存储数据结点指针域,形成平衡二叉树,将高度维持在(O(log2n)),平均查找长度也可维持在(O(log2n)),大大降低操作时间复杂度,提高数值查询效率。同时,为保证测试结果的公平性,把构建高度平衡二叉树的时间计入总时间,以进行对比。通过相应算例,验证了该改进方法的高效性。     

太阳高度角变化对小麦叶面积指数观测的影响

利用LAI-2000植物冠层分析仪,通过固定点拔节期小麦LAI观测实验,连续测量了晴天条件下定点小麦在24个不同太阳高度角下的LAI数据,并采取控制变量的方法,即利用相同的LAI-2000观测天顶角进行LAI值计算,进而对不同太阳高度角下LAI-2000测得的定点小麦LAI进行了定性分析.研究结果表明,同天内观测的小麦LAI随着太阳高度角的减小而呈明显增大趋势,两者具有很高相关性,负相关系数(R2)达0.859.若利用LAI-2000在晴天观测植被LAI时,可以通过对LAI值进行修正和归一化处理,解决LAI-2000只能在晴天日出前和日落后观测的局限性,进一步拓展LAI-2000晴天时从早晨一直到傍晚观测的适用性和有效性.     

多时相遥感影像监测南极冰川流速

测定南极冰川的流速，对于研究南极冰雪物质平衡、南极环境变化及其对全球环境的影响和极区航行有重大意义。本论述了利用多时相卫星遥感影像监测冰川变化的原理和方法，通过对英格里特一克里斯泰森海岸不同时期的遥感影像进行几何纠正和配准及叠加处理，测量和计算出极记录冰川的平均流速，并对它们的变化特点进行了初步的分析和评价。     

一种小型无人机高度测量方法的研究与实现

为了满足某小型无人机飞行控制中对高度信号的采集与处理,提出了用无线电高度来确定基准高度,用气压高度来确定相对高度,用起飞点的实测温度进行补偿的设计思想,综合这3种手段来有效消除外界环境对气压高度测量精度的影响。传感器数据融合方面,利用飞行器运动学推算出的高度状态方程以及传感器观测模型,采用Kalm an滤波技术来估计和修正传感器的测量高度。测试结果表明,此方法得到了较准确的高度测量信息,可以满足无人机飞行控制的需求。     

基于CryoSat-2雷达高度计青藏高原地区冰川高度变化提取方法对比

基于2010～2016年CryoSat-2雷达高度计SARIn模式的Level 2测高数据,结合青藏高原地区冰川矢量数据以及全球GEDM数据,通过重叠脚印法、伪平面拟合法以及较新的曲面拟合法提取青藏高原地区典型冰川冰帽的高度变化值。结果表明:①CryoSat-2测高数据应用该3种方法提取山地冰川高度变化具备可行性;②提取高度变化的3种方法各有优劣,以此提供了提取山地冰川高度变化的方法选择的依据;③应用上述3种方法获取的青藏高原地区典型冰川冰帽2010～2016年的定量高度变化结果,绝大多数的冰川都处于消融状态且3种方法提取的高度变化结果增、减趋势一致。处于西昆仑山脉的中峰冰川、古里雅、土则岗目冰川缩减速率较慢,而帕米尔高原的慕士塔格冰川缩减略快,两者的缩减速度都趋于平缓。处于念青唐古拉山脉的来古、恰青冰川高度变化速率最大。     

数据融合技术在高度测量系统中的应用

飞行器针对不同的飞行高度采取了无线电高度和大气高度测量,两种高度在单独使用时存在很多不足之处。首先简要介绍了无线电高度和大气高度的测高原理,对比了两种不同测高原理的优劣;其次,介绍了数据融合的基本概念,并利用数据融合技术,从原理上对两种测高方法进行融合解算分析;最后,针对具体的项目,完成了数据融合技术在无线电高度和大气高度综合测量系统中的软硬件实现。     

Estimating glacier volume loss using remotely sensed images,digital elevation data,and GIS modelling

Glacier retreat has received much attention in the public and scientific community as a sensitive indicator of global warming. Parameters for changes in glacier size include length, area, volume, and mass balance. While measurement of changes in glacier length and area is relatively straightforward using remotely sensed data, estimating changes in volume and mass balance remains a major challenge. The objectives of this research are to (1) develop a new model to describe the nonlinear thinning process of a glacier surface headward from the terminus position and (2) reconstruct historical glacier longitudinal profiles and 3D surfaces based on current glacier longitudinal profile and thinning rate, and estimate glacier volume loss. Using historical terminus positions and Landsat Thematic Mapper (TM), IKONOS, and Advanced Spaceborne Thermal Emission and Reflection Radiometer (ASTER) global digital elevation model (GDEM) data for the Gangotri Glacier in the Himalayas, longitudinal profiles and 3D surfaces of the glacier for 1900, 1935, and 1971 were reconstructed, and the amount and rate of volumetric losses during 1900–1935, 1935–1971, and 1971–2005 were derived. The methods can be used for more detailed study on estimating volume loss of the Himalayan glaciers and other glaciers.     

Quantification of annual glacier surface mass balance for the Chhota Shigri Glacier,Western Himalayas,India using an Equilibrium-Line Altitude (ELA) based approach

ABSTRACT

In line with the increasing scientific interest on the Himalayan glaciers, this study focuses on estimating a long-term annual surface mass balance time series of the Chhota Shigri glacier, a ‘benchmark’ glacier in the western Himalayas. The approach used here is based on the fact that the annual glacier-wide surface mass balance can be deduced from the equilibrium-line altitude (ELA). Depending on the distribution and availability of multiple cloud free remotely sensed images during ablation period, a multi-temporal approach has been used to estimate ELA. When compared with field-based ELA, the results indicate that the multi-temporal approach resulted in better estimates of ELA than the conventional single image approach. Likewise, the annual surface mass balances quantified from this study closely match with field estimates over the common period (2003–2014) and even better than some estimates from earlier studies based on other proxies (meteorological data or glacier surface albedo). A sensitivity analysis shows that the annual surface mass balance quantified from the ELA-based approach is not very sensitive to changes in the mass balance gradient and average mass balance. Hence, the approach has been further applied to reconstruct the long-term annual surface mass balance series of the Chhota Shigri Glacier over the period 1989–2017. Our results show a good agreement between the reconstructed surface mass balance and estimates of other long-term studies. Therefore, this study indicates the great potential for this approach for quantifying the annual surface mass balance for glaciers with no ground data lying in same climatic zone.     

LS-SVM在提高气压测高系统精度中的应用研究

在利用计算机软件补偿飞机测高系统误差方法中,传统的采用分段拟合方法精度不高,非线性误差大;神经网络存在过学习、网络拓扑结构不易确定以及泛化能力差等缺点。提出利用最小二乘支持向量机(LS-SVM)对某型飞机测高系统误差进行预测、补偿,提高其测高精度。在分析LS-SVM回归算法的基础上,利用LS-SVMlab1.5对某型飞机测高系统误差样本数据进行了仿真。结果表明,LS-SVM在数据回归预测方面精度高、泛化能力强、稳定性好,可以有效提高飞机气压测高系统精度,具有应用推广价值。     

Monitoring glacier elevation and volume changes with digital photogrammetry and GIS at Gepatschferner glacier,Austria

Digital elevation models of Gepatschferner in Northern Tyrol, Austria were obtained with digital photogrammetry from high altitude stereo photo pairs and by digitizing an analogue topographic glacier map, for 1990 and 1971, respectively. A difference map was calculated to identify regions of glacier elevation increases and decreases corresponding to glacier mass gain and loss. While the glacier tongue below 2600 m showed mainly increases in glacier surface elevation as compared to 1971, the remaining glacier thickness experienced both increases and decreases. The accumulation zone above 3200 m contained several extreme cases of morphological features with altitude changes>+30 m. While the increased ice thickness of the glacier tongue can be traced to a well documented period of mass accumulation in the 1970s, changes in glacier surface elevation in the higher zones may be linked either to the morphology of the glacier bed or to differences in insolation on the glacier surface. Between 1971 and 1990 the glacier experienced a net loss of 26×10⁶ m³ corresponding to approximately 0.9% of the entire glacier volume.     

低空安全天网工程的发展与探讨

为了贯彻落实总体国家安全观,开展了低空安全天网工程的跨学科综合研究。对低空安全天网工程的总体构架进行了探索,阐述了低空安全天网工程相关的卫星互联网服务技术、北斗导航与地基增强定位系统、低空通信网络保障技术、低空飞行器设计与适航管理、低空空域环境保护以及低空安全管理的法律法规需求,分析了低空飞行器在飞行前、飞行过程中和飞行结束等三类飞行状态中的飞行流量监测方法,设计了低空安全走廊与航路网规划方案,研究了低空空域的飞行器管理目标、管理方法以及低空安全管理系统的总体架构,讨论了低空飞行事故征候与处置方法,提出了低空安全天网的原型试验场建设思路,明确了试验场的软硬件平台、运营与管理系统部署、通信数据安全等方面的建设需求,制定了低空安全天网工程的验收程序和考核指标,剖析了低空安全教育与加强低空人才培养的重要性,对于保障低空产业链的安全有序发展具有积极的现实意义。     

Delineation of glacial zones of Gangotri and other glaciers of Central Himalaya using RISAT-1 C-band dual-pol SAR

The Himalayan glaciers, being unique in nature, need more detailed study over their evolution in the Himalayan glacial zones. A methodology has been developed using two-dimensional signatures from synthetic aperture radar (SAR) C-band dual-polarized data. A linear decision rule-based model has been generated using the signatures and the result further filtered by the use of a digital elevation model (DEM) to delineate glacial zones in the Himalayas. The advantage of using cross-polarized data is the addition of extra information from the volume of the glacial mass. Some important prerequisites for the analysis are SAR image ortho-rectification and calibration, glacier boundary delineation, and the development of sites for collecting SAR backscattering signatures from glaciers along the profile. The study deals with the evolution of glacial snow cover and glacial zones/facies in the Himalayan region under a subtropical humid climate from the ablation to the accumulation season. SAR images from 15 July 2012 to 30 June 2013 over the Gangotri and Mana glaciers were evaluated with the developed model. The identification of a superimposed zone during the ablation season is among the key results. The identified snowlines and other boundaries of glacial facies are studied on a temporal scale. The highest snowline altitude of Mana was recorded at 5768 and 5194 m for the Gangotri glacier in 2012. SAR data are also important in identifying glacial zones buried under winter snow cover. The results obtained are useful in regard to further glaciological studies of the Himalayan glaciers.     

Remote sensing estimates of glacier mass balances in the Himachal Pradesh (Western Himalaya, India)

Although they correspond to an important fraction of the total area of mountain glaciers (33,000 km² out of 546,000 km²), Himalayan glaciers and their mass balance are poorly sampled. For example, between 1977 and 1999, the average area surveyed each year on the field was 6.8 km² only. No direct mass balance measurement is available after 1999. To contribute to fill this gap, we use remote sensing data to monitor glacier elevation changes and mass balances in the Spiti/Lahaul region (32.2°N, 77.6°E, Himachal Pradesh, Western Himalaya, India). Our measurements are obtained by comparing a 2004 digital elevation model (DEM) to the 2000 SRTM (Shuttle Radar Topographic Mission) topography.The 2004 DEM is derived from two SPOT5 satellite optical images without any ground control points. This is achieved thanks to the good on-board geolocation of SPOT5 scenes and using SRTM elevations as a reference on the ice free zones. Before comparison on glaciers, the two DEMs are analyzed on the stable areas surrounding the glaciers where no elevation change is expected. Two different biases are detected. A long wavelength bias affects the SPOT5 DEM and is correlated to an anomaly in the roll of the SPOT5 satellite. A bias is also observed as a function of altitude and is attributed to the SRTM dataset. Both biases are modeled and removed to permit unbiased comparison of the two DEM on the 915 km² ice-covered area digitized from an ASTER image.On most glaciers, a clear thinning is measured at low elevations, even on debris-covered tongues. Between 1999 and 2004, we obtain an overall specific mass balance of − 0.7 to − 0.85 m/a (water equivalent) depending on the density we use for the lost (or gained) material in the accumulation zone. This rate of ice loss is twice higher than the long-term (1977 to 1999) mass balance record for Himalaya indicating an increase in the pace of glacier wastage. To assess whether these ice losses are size-dependant, all glaciers were classified into three samples according to their areal extent. All three samples show ice loss, the loss being higher for glaciers larger than 30 km². In the case of the benchmark Chhota Shigri glacier, a good agreement is found between our satellite observations and the mass balances measured on the field during hydrological years 2002-2003 and 2003-2004. Future studies using a similar methodology could determine whether similar ice losses have occurred in other parts of the Himalaya and may allow evaluation of the contribution of this mountain range to ongoing sea level rise.