星载海洋激光雷达叶绿素剖面探测能力估算

为了评估和分析星载海洋激光雷达探测全球海洋光学参数的性能，依据激光雷达方程和蒙特卡罗模型结果模拟计算激光传输信号，开发了星载海洋激光雷达仿真模拟系统。仿真模拟系统由正向模拟、数据反演与误差分析三部分组成，能够模拟激光发射、传输和探测的全过程。根据给定的激光雷达参数，模拟了443 nm、486.1 nm和532 nm波长在地中海、印度洋、南大洋与太平洋四个典型海区的探测信号。研究结果表明，443 nm和486 nm波长的探测深度在各个海区均比较接近，并且均比532 nm更深。在给定的激光雷达参数情况下，486.1 nm波长在太平洋和南大洋的探测深度分别为120 m和70 m，在地中海和印度洋的探测深度均为约100 m。叶绿素a浓度在以上海区的探测深度分别约为80 m、50 m和70 m。     

蓝绿光星载海洋激光雷达全球探测深度估算

为了评估和分析激光雷达探测全球海洋光学参数的性能,根据激光雷达方程和给定的激光雷达参数,使用MODIS Level 3全球年平均的海水吸收系数a（）和后向散射系数bb（）数据作为海水光学参数的参考值,对蓝绿光星载海洋激光雷达在全球海洋的探测深度进行了估算和分析。研究结果表明:星载海洋激光雷达探测深度的分布主要依赖于探测波长和水体光学性质,清洁大洋水的最优探测波长在460 nm左右,白天和夜间的最大探测深度分别为~110 m和~120 m;沿岸浑浊水的最优探测波长多在500 nm以上,最大探测深度只能达到20 m或更浅。探测波长为470~480 nm时,星载海洋激光雷达在全球范围内的平均探测能力最佳。     

车载激光测绘技术

三维激光测绘技术广泛应用于工程建设与物体三维测量等相关领域,具有高效率、高精度的独特优势.首先描述了车栽激光测绘技术的应用方向,研究了国外技术发展现状,结合国外相似技术的研究成果,提出了利用三维激光扫描技术和定位定姿技术实现道路测绘的技术途径,阐述了工作过程及测量原理,给出了系统基本构成,并分析了关键技术及解决途径,在工程样机的基础上提出了具体的试验方法,结合样机的测试试验情况给出了试验结果.最后对试验结果进行了误差分析.结果表明:采用车栽激光测绘技术可以得到高精度的物体三维信息,能够满足道路测绘需要.     

脉冲调制激光雷达水下成像系统

针对水下目标探测应用场景,给出了相应的532 nm波长激光雷达系统参数,结合条纹管激光雷达和载波调制激光雷达的优点,设计研制了一套水下三维成像增程激光雷达原理样机。相对于常见的微波调制激光产生高频脉冲的方案,该原理样机采取调Q技术压缩激光脉冲,再结合F-P腔的特性产生高频激光脉冲,具有峰值功率高和输出能量高的优点。实验结果表明,该原理样机在清水环境中成像距离优于20 m,能够捕捉到13 m处直径9 mm的目标细节;在浊水环境中的信号处理增程能力达到81.4%,相对距离分辨误差为0.01 m。所获得的实验结果为进一步提升水下激光雷达的成像距离和分辨率进而发展水下成像装备奠定了基础。     

GNSS信号遮挡处水下地形测量方法的研究

现代海洋测绘中,内河及近海RTK三维水深测量技术已经相当成熟。结合GNSS实时定位技术,实现了高效的三维水深测量,为水下地形测绘、障碍物探测及航海导航提供了支持。但在一些GNSS信号遮挡的区域,如码头岸坡、船闸闸室内、船厂水工建筑物等位置进行水深测量时,由于GNSS信号遮挡而需要重新获取测深仪的三维坐标,然后进行水深测量。文章介绍了在GNSS信号遮挡区域的定位及水深测量方法,并讨论相关误差来源。     

直接测风激光雷达频率跟踪技术及对流层平流层大气风场观测

为了实现高精度连续探测对流层和平流层大气风场,搭建了一台直接测风激光雷达系统对对流层和平流层大气风场进行探测。该系统基于双边缘法布里-珀罗标准具的瑞利散射多普勒测风原理,使用转台式探测结构,通过频率跟踪的手段对频率漂移进行跟踪,确保测风的精度。实验结果表明,该系统对对流层和平流层大气风场探测效果良好,频率跟踪的范围为±50 MHz,可以大大减小频率漂移带来的风速误差。经过系统的稳定运行和长时间的观测,在40 km处测得的径向风速随机误差为8 m/s。径向风速合成为水平风速后,随机误差在38 km处最大为10 m/s左右。该系统白天探测高度为25 km,夜晚探测高度为38 km。与探空数据对比,风速误差均小于10 m/s,其中风速误差在±5 m/s的范围内的数据量约占75.8%,探测的风向误差与探空气球的趋势基本一致,误差范围在10°～20°之间,在15°范围内的数据量约占58.6%。将实测数据与探空数据进行统计分析,结果具有良好的一致性。该系统可以为对流层和平流层大气风场的探测提供数据支撑。     

机载双天线InSAR对飞数据处理与分析

干涉合成孔径雷达(InSAR)技术具有高精度的地形测绘能力。然而在山区地形条件下,受SAR侧视成像的影响,存在较多的几何畸变区域,干涉相位表现为不连续或者缺少有效信息的情况,对单一的干涉图像对处理难以得到精确的数字高程模型(DEM)。融合两个或多角度的干涉数据可以用于解决这一问题。该文根据这一思路利用机载双天线InSAR对飞数据进行实验,针对山区地形条件下参考高程近似影响运动补偿精度的问题提出了基于高程迭代的运动补偿方法,对于阴影、叠掩区域容易导致相位解缠误差的问题提出基于地形特征的相位解缠方法,从而尽可能降低单一角度数据的DEM误差,以达到消除对飞数据重叠区域3维定位不一致的目的,拼接实验结果验证了处理方法的有效性。      

便携式高频地波雷达东海洋山海域探测深度试验

为了验证采用紧凑型接收天线的便携式高频地波雷达系统(OSMAR-S)的探测性能,于2007年11月在洋山海域进行了OSMAR-S与其他海洋测量设备的现场探测对比验证试验。试验设计了定点固定水深测量与坐底剖面测量相结合的连续现场对比监测方式,把雷达获得的表面流探测数据与其他设备得到的不同深度的海流观测数据进行对比。通过试验数据分析,OSMAR-S系统的探测深度和精度都得到了验证,能够满足实时监测海洋表面流的需要。同时试验也填补了高频雷达探测深度没有试验验证的空白。     

雷达动态精度试验误差分析

针对国军标GJB74A-98中雷达动态精度试验中误差置信区间推导的问题,分析了影响雷达精度试验的误差因素,给出了一次差数据的系统误差、随机误差、均方根误差的置信区间和长度推导过程,并对雷达动态精度试验的探测数据进行了仿真和分析。通过仿真分析影响雷达动态试验精度的因素,可有效地指导雷达动态精度试验。     

空间充气展开天线初步研究

结合3.5 m充气天线地面样机的研制,分析了柔性充气展开天线的结构形式和材料特性,对充气天线结构仿真分析、形面精度测量技术、电性能测试等进行了初步探讨。该地面样机形面均方根误差小于2.5 mm,成功完成了充气展开试验和折叠试验,并具有电性能,为进一步进行空间柔性可展天线研制积累了经验。     

Mid-Infrared Remote Sensing Systems and Their Application to Lithologic Mapping

Mid-infrared remote lithologic mapping by emittance and by reflectance are assessed in laboratory experiments. The emittance spectra of various rocks and minerals, measured in the 8-13, ?m atmospheric transmission window, are compared with reflectance data measured in the range of 9.2-11.2 Am using a line-tuned CO2 laser. We conclude that the reflectance data are more useful for lithologic discrimination than the passive emittance data. An experimental laser suitable for terrain mapping from a low-flying aircraft is described. The low-pressure longitudinal discharge CO2 laser has a rotating mirror to scan the diffraction grating and generates 90 bursts of pulses per second. Each 1-ms burst contains 92 pulses at 92 CO2 laser wavelengths. The mean output power is 12 W and the average pulse power is 370 W. With that power, and using incoherent detection, a signal-to-noise ratio of better than 100: 1 should be obtained from terrain with an albedo of 0.01 at a height of 500 m.     

基于区域聚合的栅格地形数据简化算法

针对规则网格地形数据存在的数据冗余,提出了一种基于区域聚合的地形数据简化算法,区域聚合是将共面或近似共面的若干地形栅格点用这组栅格点的边界点代替。该算法用面元间最大法向量夹角余弦值作为简化度量误差,通过递归过程完成数据简化,结合简化后存留散列点的特点进行地形绘制且经过消除地形裂缝处理,避免了离散点Delaunay三角化过程。实验结果表明,算法数据结构简单,便于使用,简化精度可控,简化效果好。     

Development of a technique to assess snow-cover mapping errors fromspace

Following the December 18, 1999, launch of the Earth Observing System (EOS) Terra satellite, daily snow-cover mapping is performed automatically at a spatial resolution of 500 m, cloud-cover permitting, using moderate resolution imaging spectroradiometer (MODIS) data. This paper describes a technique for calculating global-scale snow mapping errors and provides estimates of Northern Hemisphere snow mapping errors based on prototype MODIS snow mapping algorithms. Field studies demonstrate that under cloud-free conditions, when snow cover is complete, snow mapping errors are small (<1%) in all land covers studied except forests, where errors are often greater and more variable. Thus, the accuracy of Northern Hemisphere snow-cover maps is largely determined by percent of forest cover north of the snowline. From the 17-class International Geosphere-Biosphere Program (IGBP) land-cover maps of North America and Eurasia, the authors classify the Northern Hemisphere into seven land-cover classes and water. Estimated snow mapping errors in each of the land-cover classes are extrapolated to the entire Northern Hemisphere for areas north of the average continental snowline for each month. The resulting average monthly errors are expected to vary, ranging from about 5-10%, with the larger errors occurring during the months when snow covers the boreal forest in the Northern Hemisphere. As determined using prototype MODIS data, the annual average estimated error of the future Northern Hemisphere snow-cover maps is approximately 8% in the absence of cloud cover, assuming complete snow cover. Preliminary error estimates will be refined after MODIS data have been available for about one year     

Planetary exploration using a small electromagnetic sensor

A prototype broadband electromagnetic (EM) sensor, GEM-5, has been built and tested as a possible new probe for the future Mars rover to seek an ice-bonded layer at a given depth below the Martian surface. The sensor, with a vertical coaxial coil configuration, will measure the terrain resistivity and susceptibility to determine lateral variations in resistivity and magnetic susceptibility. The lateral variations will indicate regions of resistivity/susceptibility anomalies that may contain ice or water at depth. The forward solution for the sensor geometry over a layered formation and inverse algorithms to convert the EM data into the apparent susceptibility and resistivity are developed to investigate the ability of the sensor in detecting and resolving a buried (wet) ice layer in Mars-like geologic formations. Based on the simulated study, we find that the prototype sensor design should be able to resolve the lateral variations in resistivity/susceptibility under conditions of the Martian subsurface.     

海洋激光雷达图像处理提取海水深度的方法

机载激光雷达已经应用于浅海地形测绘,与激光器、接收望远镜和探测器一样,水深提取算法也是决定系统最大测深能力的关键环节。常规的水深提取算法是对单个激光雷达采集的波形数据进行处理,通过提取波形中的海表和海底位置实现水深测量,这种方法在提取水深较深的海底微弱回波信号时,易受海水散射层强信号的影响,导致水深提取能力和准确度下降。为了解决这一问题,将一维回波波形数据按采集顺序组合成二维的回波强度图像,图像的每一列代表一条回波波形,图像的灰度值对应着回波信号强度。利用图像的横向相关性,通过双边滤波、局部阈值二值化等图像处理方法,提取出海底回波信号廓线。该方法一方面提升了海底回波的提取能力,一方面避免散射层信号对海底微弱信号的干扰,为浅海地形、水下目标一体化探测提供新的数据处理方式。     

基于动态地标的在线室内平面图生成方法

在应急救援、商场导购、患者导医、参观引导等导航应用场景中,往往需要室内平面图作为先验知识,从而使得大量室内导航系统缺乏可扩展性和鲁棒性。针对该问题,该文提出基于动态地标的在线室内平面图生成方法,减少现有方法对先验知识的依赖。首先利用智能移动设备内置的惯导传感器数据和航位推算法获取粗粒度移动轨迹,继而提出一个同步静态地标(楼梯、电梯以及手扶电梯等)和动态地标(轨迹拐点)的识别方法;其次,利用这些地标信息提出多用户参与的轨迹自校正和组合方法实现室内平面图生成;最后,利用原型系统获取的数据评价所提方法。分析结果显示,该文方法的最大误差以及平均误差分别为1.90 m和0.90 m。     

New approaches in interferometric SAR data processing

It is known that interferometric synthetic-aperture radar (SAR) images can be inverted to perform surface elevation mapping. Among the factors critical to the mapping accuracy are registration of the interfering SAR images and phase unwrapping. A registration algorithm is presented that determines the registration parameters through optimization. A figure of merit is proposed that evaluates the registration result during the optimization. The phase unwrapping problem is approached through a new method involving fringe line detection. The algorithms are tested with two SEASAT SAR images of terrain near Yellowstone National Park. These images were collected on SEASAT orbits 1334 and 1420, which were very close together in space, i.e. less than 100 m     

Tomographic formulation of interferometric SAR for terrainelevation mapping

Topographic mapping with spotlight synthetic aperture radar (SAR) using an interferometric technique is studied. Included is a review of the equations for determination of terrain elevation from the phase difference between a pair of SAR images formed from data collected at two differing imaging geometries. This paper builds upon the systems analysis of Li and Goldstein in which image pair decorrelation as a function of the “baseline” separation between the receiving antennas was first analyzed. In this paper correlation and topographic height error variance models are developed based on a SAR image model derived from a tomographic image formation perspective. The models are general in the sense that they are constructed to analyze the case of single antenna, two-pass interferometry with arbitrary antenna line of sight, and velocity vector directions. Correlation and height error variance sensitivity to SAR system parameters and terrain gradients are studied     

ICESat Full-Waveform Altimetry Compared to Airborne Laser Scanning Altimetry Over The Netherlands

Since 2003, the full-waveform laser altimetry system onboard NASA's Ice, Cloud and land Elevation Satellite (ICESat) has acquired a worldwide elevation database. ICESat data are widely applied for change detection of ice sheet mass balance, forest structure estimation, and digital terrain model generation of remote areas. ICESat's measurements will be continued by a follow-up mission. To fully assess the application possibilities of the full-waveform products of these missions, this research analyzes the vertical accuracy of ICESat products over complex terrain with respect to land cover type. For remote areas, validation of individual laser shots is often beyond reach. For a country with extensive geo-infrastructure such as The Netherlands, excellent countrywide validation is possible. Therefore, the ICESat full-waveform product GLA01 and the land elevation product GLA14 are compared to data from the Dutch airborne laser altimetry archive Actual Height model of the Netherlands (AHN). For a total population of 3172 waveforms, differences between ICESat- and AHN-derived terrain heights are determined. The average differences are below 25 cm over bare land and urban areas. Over forests, differences are even smaller but with slightly larger standard deviations of about 60 cm. Moreover, a waveform-based feature height comparison resulted in feature height differences of 1.89 m over forest, 1.48 m over urban areas, and 29 cm over low vegetation. These results, in combination with the presented processing chain and individual waveform examples, show that state-of-the-art ICESat waveform processing is able to analyze waveforms at the individual shot level, particularly outside urban areas.     

Laryngeal pathology detection by means of class-specific neuralmaps

Most of the existing systems and methods for laryngeal pathology detection are characterized by a classification error. One of the basic problems is the approximation and estimation of the probability density functions of the given classes. In order to increase the accuracy of laryngeal pathology detection and to eliminate the most dangerous error classification of a patient with laryngeal disease as a normal speaker, an approach based on modeling of the probability density functions (pdfs) of the input vectors of the normal and pathological speakers by means of two prototype distribution maps (PDM), respectively, is proposed. The pdf of the input vectors of an unknown normal or pathological speaker is also modeled by such a prototype distribution neural map (PDM(X)), and the pathology detection is done by means of a ratio of specific similarities rather than by a direct comparison of some type of distance/similarity with a threshold. The experiments show an increased classification accuracy and that the proposed method can be used for screening the laryngeal diseases. The method is applied in a consulting system for clinical practice