Measurements of ocean wave spectrum from airborne radar at small incidence angles

This paper proposes the retrieval method of ocean wave spectrum for airborne radar observations at small incidence angles, which is slightly modified from the method developed by Hauser. Firstly, it makes use of integration method to estimate total mean square slope instead of fitting method, which aims to reduce the affects of fluctuations superposed on normalized radar cross-section by integration. Secondly, for eliminating the noise spectrum contained in signal spectrum, the method considers the signal spectrum in certain look direction without any long wave components as the assumed noise spectrum, which would be subtracted from signal spectrum in any look direction for linear wave spectrum retrieval. Estimated v from the integration method are lower than the one from fitting method and have a standard deviation of 0.004 between them approximately. The assumed noise spectrum energy almost has no big variations along with the wave number and is slightly lower to the high wave number part of signal spectrum in any look direction, which follows that the assumption makes sense. The retrieved directional spectra are compared with the buoy records in terms of peak wavelength, peak direction and the significant wave height. Comparisons show that the retrieved peak wavelength and significant wave height are slightly higher than the buoy records but don＇t differs significantly （error less than 10%）. For peak direction, the swell waves in first case basically propagate in the wind direction 6 hours ago and the wind-generated waves in second case also propagate in the wind direction, but the 180° ambiguity remains. Results show that the modified method can carry out the retrieval of directional wave spectrum.

Parameter Identification of JONSWAP Spectrum Acquired by Airborne LIDAR

In this study, we developed the first linear Joint North Sea Wave Project(JONSWAP) spectrum(JS), which involves a transformation from the JS solution to the natural logarithmic scale. This transformation is convenient for defining the least squares function in terms of the scale and shape parameters. We identified these two wind-dependent parameters to better understand the wind effect on surface waves. Due to its efficiency and high-resolution, we employed the airborne Light Detection and Ranging(LIDAR) system for our measurements. Due to the lack of actual data, we simulated ocean waves in the MATLAB environment, which can be easily translated into industrial programming language. We utilized the Longuet-Higgin(LH) random-phase method to generate the time series of wave records and used the fast Fourier transform(FFT) technique to compute the power spectra density. After validating these procedures, we identified the JS parameters by minimizing the mean-square error of the target spectrum to that of the estimated spectrum obtained by FFT. We determined that the estimation error is relative to the amount of available wave record data. Finally, we found the inverse computation of wind factors(wind speed and wind fetch length) to be robust and sufficiently precise for wave forecasting.

Quantitative algorithm for airborne gamma spectrum of large sample based on improved shuffled frog leaping-particle swarm optimization convolutional neural network

In airborne gamma ray spectrum processing,different analysis methods,technical requirements,analysis models,and calculation methods need to be established.To meet the engineering practice requirements of airborne gamma-ray measurements and improve computational efficiency,an improved shuffled frog leaping algorithm-particle swarm optimization convolutional neural network(SFLA-PSO CNN)for large-sample quantitative analysis of airborne gamma-ray spectra is proposed herein.This method was used to train the weight of the neural network,optimize the structure of the network,delete redundant connections,and enable the neural network to acquire the capability of quantitative spectrum processing.In full-spectrum data processing,this method can perform the functions of energy spectrum peak searching and peak area calculations.After network training,the mean SNR and RMSE of the spectral lines were 31.27 and 2.75,respectively,satisfying the demand for noise reduction.To test the processing ability of the algorithm in large samples of airborne gamma spectra,this study considered the measured data from the Saihangaobi survey area as an example to conduct data spectral analysis.The results show that calculation of the single-peak area takes only 0.13~0.15 ms,and the average relative errors of the peak area in the U,Th,and K spectra are 3.11,9.50,and 6.18%,indicating the high processing efficiency and accuracy of this algorithm.The performance of the model can be further improved by optimizing related parameters,but it can already meet the requirements of practical engineering measurement.This study provides a new idea for the full-spectrum processing of airborne gamma rays.

Introduction to the airborne marine surveillance platform and its application to water quality monitoring in China

China Marine Surveillance Force was equipped with modern aerial equipments for marine lawexecute with the advantage of functioning agilely at a large scale of surveillance coverage, providing powerful all-round safeguard, which is of benefit to the harmonious and sustainable development of coastal economy. Onboard the planes, three kinds of remote sensing sensors have been installed, including a marine airborne multi-spectrum scanner （MAMS）, an optical-electronic platform, and an airborne hyper-spectral system AISA＋. The specifications of remote sensing platforms were introduced briefly first, then examples of water quality monitoring by airborne remote sensing were presented, including the monitoring in coastal suspended material, oil-spill and abnormal warm water, etc.

Airborne Shortwave Infrared Spectral Remote Sensing as a Direct Prospecting Method for Oil and Gas Resources

The spectral characters of hydrocarbons in some oil-bearing strata and soil layers over oil and gas reservoirs in the Junggar Basin and northern Tarim Basin in Xinjiang are compared with those of chemically pure hydrocarbons. The hydrocarbons are characterized by the bi-absorption at 2310nm and 2350nm. Hydrocarbon and radioactive anomalies in oil and gas terrains are found much more widespread than carbonate altcrations. Based on the spectra of heavy hydrocarbons related to oil between 2270nm and 2460nm and refined data treatme nt, remote sensing may hold encouraging promise as a directly prospecting technique for oil and gas resources.

The likely counterpart to γ-ray excess from the northwest region of Arp 220

The unknown γ-ray excess in the northwest region of Arp 220 was revisited by analyzing~11.8 years of the Fermi Large Area Telescope(Fermi-LAT) data in this study.We found that its photon flux was approximately three times higher than that of the previous study in the 0.2-100 GeV band,and the corresponding significance level ~8.15σ was approximately four times higher than before.The light curves of 15 and 45 time bins from the whole time all showed two active periods,and the variability of the second period was more significant than that of the first period.The spectral indices from the two active periods were not statistically different and were close to the range of γ-ray flat-spectrum radio quasars observed by Fermi-LAT.Because the position of CRATES J153246+234400 was consistent with the best-fit position of our analysis,we suggest that CRATES J153246+234400 is more likely a γ-ray counterpart for the variational region.For Arp 220,there was no significant variability in the γ-ray emission.

基于航空高光谱和伽马能谱的铀矿勘查集成软件开发与应用

航空高光谱和航空伽马能谱是当前铀矿勘查领域两类重要的数据源,由于其异构且海量的特性,使数据的处理难度大,处理效率低,协同应用效果不足。在这种情况下开发一款面向航空高光谱和伽马能谱的铀矿勘查集成软件显得尤为重要。文章根据航空高光谱和航空伽马能谱数据的类型及处理方法,开展了针对两种数据应用的集成软件系统的设计。研究引入虚拟总线结构,实现了对不同数据处理模块的调用,并以Visual Basic为主要开发语言,对前台主系统进行搭建。最终利用搭建好的系统,以银根地区的航空高光谱和伽马能谱数据为数据源,完成软件的应用测试。测试结果发现,利用GS融合算法可以较好地保留地表纹理信息,同时丰富图像颜色,从而为铀矿赋矿围岩岩性的准确识别与划分提供参考。

铀矿勘查中航放信息提取技术应用研究

航空伽马能谱测量(简称航放测量)是一种快速有效勘查隐伏铀矿的勘探方法。相比于裸露于地表附近的铀矿体,隐伏铀矿体在地表引起的矿致异常信息相对较弱。为了提取深部铀矿在地表产生的弱异常信息,文章以相山铀矿田为例采用铀变异系数、航放参数F、铀富集系数、元素含量与面积(CA)分形4种方法,对相山铀矿田航放测量数据(1∶5万)进行成矿信息提取,运用打分综合信息定量法对相山铀矿田进行了成矿预测。预测结果显示,航放综合信息异常与已知矿体位置吻合度较高,对已知矿床判断的正确率为76.4%,为铀矿勘查中航放信息有效提取提供了技术指导,具有一定的实用价值。

无人机载CeBr3航空监测系统无限大面源探测能力研究

在核设施发生重大事故后,快速获取事故应急区内的辐射水平,对后续应急决策及救援、保护公众免受辐射危害具有至关重要的意义,核应急航空辐射监测是核应急早期快速获取辐射水平的重要技术手段和方法之一,因此核工业航测遥感中心自主研发了无人机载CeBr3航空监测系统。为准确评估该监测系统的探测能力,文章使用蒙特卡罗方法对该监测系统进行了建模,并通过60Co点源对模型的准确性进行了验证。在此基础上,采用全能谱分析、蒙特卡罗及实验相结合的方法获得监测系统对天然辐射单位能谱,并以核事故后地面受到一个新的137Cs放射性沉降场景为例,计算监测系统在不同测量条件下(天然辐射本底、晶体体积、测量高度)对无限大137Cs面源的探测效率及最小可探测活度浓度。通过模拟及计算监测系统对天然辐射本底及核应急人工放射性核素的单位能谱,准确评估了自研的无人机载CeBr3核应急航空监测系统的探测能力,为后续利用该监测系统开展核与辐射航空监测可提供重要理论依据及数据支撑。

航空机载设备寿命试验设计

航空机载设备的类型多、故障模式复杂、寿命验证周期长、翻修经费高,且容易集中爆发寿命问题。针对航空机载设备大量存在的“内场考核通过,外场故障频发”的情况,系统总结了寿命试验设计过程中存在的问题,包括施加应力类型不全面、分散系数不够等,针对性提出了基于机载设备耐久性机理分析的寿命试验设计方法,解决全寿命周期敏感应力/耗损性失效机理识别、多应力综合的寿命试验载荷谱制定和基于可靠寿命的试验验证/评估等技术难题,完成了寿命试验规范化设计工作。

Minimum detectable activity for NaI(Tl) airborne γ-ray spectrometry based on Monte Carlo simulation

The determination of the effective minimum detectable activity （MDA） of radionuclides by a detection system plays an im- portant role in environmental radiation monitoring. In this study, the responses of an NaI（TI） airborne γ ray spectrometry （AGRS） system to different radionuclides （137Cs and 131I） were investigated using the Monte Carlo technique. The MDA values were determined under different conditions according to the counting spectra obtained from the Monte Carlo simulation. The equivalent mass thickness method was applied to the Monte Carlo modeling for monitoring ground radiation to reduce sta- tistical uncertainty. The secondary source method was used to monitor both air and ground radiation. A quadratic relationship was found between the MDA and activity concentration. An exponential relationship was found between the MDA and altitude The MDA of a specific radionuclide from external detectors was found to be superior to that obtained from internal detectors under the same conditions. The MDA values in an NaI（Tl） AGRS system under different conditions can be estimated based on the results of this study.

基于机载细分光谱遥感影像的中小河道水体提取

卫星遥感影像被广泛应用于水质监测领域,在提取大型湖泊河流的水体边界、水体面积方面具有快速准确等优势,受分辨率影响,影像中存在混合像元等现象,在提取细小河流时容易出现误判情况。本文以太浦河支流部分河段为研究对象,分别使用NDWI、NDVI两种指数模型从高分辨率的细分光谱成像设备的高光谱影像中提取中小河道水体信息,分析同一影像两种指数提取结果的不同和同种水体指数不同阈值提取效果的差异性,并通过总体精度、识别水体面积等精度评价指标进行精度分析。结果表明,对于高分辨率的细分光谱遥感影像,阈值0.0008的NDWI水体指数模型的提取效果最好,总体精度达95.6932%,整体效果优于NDVI植被指数。

基于小波变换的机载雷达测绘遥感影像信息数据融合方法

在融合机载雷达测绘遥感影像信息数据的过程中,由于原始机载雷达测绘遥感影像反馈信号在频域分布上具有多元化的属性,导致融合后影像的质量相对较低。为此,文章提出基于小波变换的机载雷达测绘遥感影像信息数据融合方法。该方法通过在小波变换设置了以频率为基准的窗口函数,并结合遥感影像反馈信号所处频域与频率函数状态之间的关系,建立了待分析遥感影像信号与频率窗内的高频频域分布参数之间的乘积关系,从而得到所需的信号频谱特性,在进行机载雷达测绘遥感影像信息数据融合阶段,结合遥感影像反馈信号与有限区域范围之间的关系,对其进行适应性融合。测试结果表明,融合后影像在完整度、清晰度以及综合质量方面均处于较高水平。

顾及误差频谱特性的CHZ重力仪航空应用研究

给出航空重力测量误差频域分析的方法,利用功率谱密度从频域分析航空标量重力测量系统恢复重力场的能力及影响因素。介绍CHZ重力仪的主要特点。利用实测空中重力异常数据及机载GPS动态加速度数据,结合航空重力测量的频谱范围,分析CHZ重力仪在不同阻尼系数下的动态性能。计算结果表明,采用合适的阻尼系数,CHZ重力仪能够被用于固定翼飞机的航空重力测量。

卡尔曼滤波在航空γ能谱勘查系统自动稳谱中的应用

针对航空能谱多晶体短时测量所得谱线低计数率、高统计涨落的特点,采用卡尔曼滤波方法对航空能谱谱线进行光滑滤波,比较了几种常用谱线光滑方法与卡尔曼滤波光滑方法的光滑效果,最后采用该方法对谱线光滑,并寻峰实现航空能谱的自动稳谱,在1024道分辨率时,137Cs峰谱漂小于±1道。

顾及地形效应的重力向下延拓模型分析与检验

向下延拓是航空重力测量数据实际应用中必不可少的技术环节。向下延拓属于不适定反问题,其解算过程具有较大的不确定性,故该问题一直是大地测量领域国内外学者的研究热点。本文深入分析研究了当前国内外最具代表性的3种向下延拓计算模型的技术特点和适用条件,提出了应用超高阶位模型、局部地形改正和移去—恢复技术顾及地形效应,以及位场延拓结果球面化曲面的工程化方法,重点探讨了计算模型的稳定性及数据观测误差对延拓计算结果的影响。通过理论分析、数值仿真和实测数据计算等手段,定量评估了不同向下延拓模型的解算精度及其可靠性。其主要结论是:传统逆Poisson积分模型解严重受制于输入数据观测噪声的干扰,在现有作业条件下,该模型至多只能用于1km以下高度的延拓解算;频谱截断积分和位模型加地改两种延拓新模型具有良好的计算稳定性,完全适用于2′分辨率和5km飞行高度条件下的航空重力测量数据向下延拓解算,其延拓计算精度可达2×10^(-5) m/s^2,可满足各方面实际应用需求。

甘肃夏季不同天气系统层状云的微物理结构特征

利用2006、2007年7—8月13架次的机载粒子测量系统实时探测资料,对甘肃省夏季不同天气系统层状云的宏微观物理特征进行了分析.结果表明,3种类型天气系统背景下,云粒子结构分布不均匀,在云滴浓度和谱型分布上有很大的差别.高原低槽型天气背景下云粒子浓度较大,云中冰晶丰富,具有最大可播区;西北气流型背景下云粒子浓度大,且冰晶浓度较小,具有较大范围的强可播区;西南气流型背景下云滴和冰晶浓度均较小,可播区较小.

航空γ能谱测量谱线比法大气氡校正的理论研究

本文介绍了在航空γ能谱测量中,校正航空γ能谱所包含大气氡本底的谱线比法理论基础及其数学模型。通过对谱线比法校正系数的探讨,分析不同组分校正系数和高度之间的关系。在此基础上,提出了校正系数获取的实验途径,避免了谱形数学拟合方法可能引起的问题。

求解航空γ 能谱模拟中的深穿透问题

蒙特卡罗(Monte Carlo,MC)模拟方法被广泛应用于γ能谱分析参数的获取,但因探测高度较高带来的深穿透问题限制了其在航空γ能谱中的应用。研究发现,探测器距离地层边界大于可探测半径时,MC模拟得到地层上空相同高度所有航空γ能谱仪响应规律均相同。根据这一规律,本文提出一种球壳型地层、航空γ探测器的MC模拟模型,通过对4个航空γ能谱仪刻度模型的模拟发现,MC模拟谱与多次实测平均谱吻合较好。同时利用该模型模拟了芬兰Vesivehmaa地区4种典型核素于100 m高空的刻度系数,结果显示模拟值与取样实测值及Allyson自编软件模拟值在±20%内符合,证明该模型能很好地应用于航空γ能谱仪地层信息反演计算参数的快速获取。

内蒙古巴升河地区航空伽马能谱异常特征及其铀成矿潜力分析

巴升河位于大兴安岭铀成矿带柴河盆地,以往铀矿找矿研究工作程度极低。通过对区域典型铀矿点航空伽马能谱特征分析,建立了区域火山岩型铀矿化区航空伽马能谱异常标志:航放铀高场、铀增量(ΔU)高值晕、活性铀(Hu)低值晕、航放F参数高值晕。据此,对研究区航空伽马能谱数据进行了处理,对异常特征进行了分析,圈定了5片航放综合异常晕;结合地层、构造、物化探条件,对圈定的5片航放综合异常晕铀成矿潜力进行了研究,发现研究区H01、H02、H03航放综合异常晕具有较好的火山岩型铀成矿潜力。