MODIS数据反演地表温度的参数敏感性分析

在利用MODIS卫星遥感数据进行地表温度反演过程中，有两个基本参数需要确定，即地表比辐射率和大气透过率，尽管采用了比较合理的参数估计方法，但仍会有一些不可避免的因素导致误差的产生。为了进一步研究可能的参数误差对地表温度反演精度的影响，我们对该算法的两个参数进行敏感性分析。结果表明，当31、32两个波段的参数估计都有中等误差时，可能的地表温度误差对大气透过率和地表比辐射率都不敏感，所引起的地表温度误差大约为0．6～0．8℃，算法能够得到较高精度的地表温度反演结果。     

Estimation of the net radiation using MODIS (Moderate Resolution Imaging Spectroradiometer) data for clear sky days

A simple scheme is proposed to estimate instantaneous net radiation over large heterogeneous areas for clear sky days using only remote sensing observations. Our method attempts to develop an algorithm which primarily uses remote sensing information and eliminates the need for ground information as model input, by using various land and atmospheric data products available from Terra-MODIS. It explicitly recognizes the need for spatially varied parameters and provides a distributed net radiation map over large heterogeneous domain with fine spatial resolution. Since instantaneous net radiation estimates have limited scope compared to daily average values or diurnal cycle, a sinusoidal model is proposed to estimate diurnal cycle of net radiation. The sinusoidal model is capable of retrieving the diurnal variations of net radiation with a single instantaneous net radiation estimate from the satellite. Preliminary results, using data over Southern Great Plains, show good agreement with ground-based observations. It appears that the methodology presented here can estimate instantaneous and daily net radiation with comparable accuracy to those of current methods that use ground-based observations and mainly provide point estimates.     

医学影像仿真扫描工作站的设计与实现

文中简单介绍了基于计算机仿真技术的医学影像仿真扫描工作站系统的设计。该系统采用Visual C++进行界面设计以及核心算法编程的实现;通过C++语言来调用VTK ( Visualization ToolKit)的类库函数,用以实现医学图像的三维重建;使用Microsoft Access数据库管理与保存患者信息数据与图像数据。实现了一款无需医学影像设备的医学影像仿真扫描工作站软件系统,该系统模拟仿真真实扫描工作站的工作流程以及系统功能。     

The 250 m global land cover change product from the Moderate Resolution Imaging Spectroradiometer of NASA's Earth Observing System

One of the products to be derived from data acquired by the Moderate Resolution Imaging Spectroradiometer (MODIS) onboard the National Aeronautics and Space Administration (NASA) Earth Observing System (EOS) will identify locations where land cover changes attributable to human activities are occurring. The product aims to serve as an alarm where rapid land cover conversion can subsequently be analysed with higher resolution sensors such as Landsat 7. This paper describes the production procedure and change detection algorithms for the 250 m MODIS land cover change product. Multiple change detection algorithms, including three spectral methods and two texture methods, are utilized to generate the product from the two 250 m MODIS bands. The change detection methods are implemented with look-up tables (LUTs) which are initially generated using data from the Advanced Very High Resolution Radiometer (AVHRR) and Landsat Thematic Mapper (TM) until MODIS data become available. The results from the five methods are combined to improve confidence in the product. We test the performance of each method against several sets of simulated MODIS data derived from Landsat TM image pairs. The test data represent tropical deforestation, agricultural expansion and urbanization. The commission errors of the five methods and the combination are approximately 10%, with reasonable omission errors less than 25%.     

Evaluation of the onset of green-up in temperate deciduous broadleaf forests derived from Moderate Resolution Imaging Spectroradiometer (MODIS) data

Vegetation phenology is the chronology of periodic phases of development. It constitutes an efficient bio-indicator of impacts of climate changes and a key parameter for understanding and modelling vegetation-climate interactions and their implications on carbon cycling. Numerous studies were devoted to the remote sensing of vegetation phenology. Most of these were carried out using data acquired by AVHRR instrument onboard NOAA meteorological satellites. Since 1999, multispectral images were acquired over the whole earth surface every one to two days by MODIS instrument onboard Terra and Aqua platforms. In comparison with AVHRR, MODIS constitutes a significant technical improvement in terms of spatial resolution, spectral resolution, geolocation accuracy, atmospheric corrections scheme and cloud screening and sensor calibration. In this study, 250 m daily MODIS data were used to derive precise vegetation phenological dates over deciduous forest stands. Phenological markers derived from MODIS time-series and provided by MODIS Global Land Cover Dynamics product (MOD12Q2) were compared to field measurements carried out over the main deciduous forest stands across France and over five years. We show that the inflexion point of the asymmetric double-sigmoid function fitted to NDVI temporal profile is a good marker of the onset of green-up in deciduous stands. At plot level, the prediction uncertainty is 8.5 days and the bias is 3.5 days. MODIS Global Land Cover Dynamics MOD12Q2 provides estimates of onset of green-up dates which deviate substantially from in situ observations and do not perform better than the null model. RMSE values are 20.5 days (bias -17 days) using the onset of greenness increase and 36.5 days (bias 34.5 days) using the onset of greenness maximum. An improvement of prediction quality is obtained if we consider the average of MOD12Q2 onset of greenness increase and maximum as marker of onset of green-up date. RMSE decreases to 16.5 days and bias to 7.5 days.     

红外扫描成像预处理系统的SOC设计

根据红外导引头成像预处理系统实时处理要求高的特点，提出基于单片系统（SOC）的设计方法，并详细描述了该成像预处理系统的硬件设计原理及基于SOC的实时处理软件设计原理．系统的预处理集成了红外探测器驱动电路，红外图像非均匀校正，以及红外图像预处理等多种实时图像处理功能，提高了成像系统集成度．实验验证了该系统的可重构性和实时处理优点．     

电阻抗扫描成像完备参数提取算法

为了提升电阻抗扫描成像的性能,本文提出了一个完备参数提取算法。该算法由前向问题建模以及参数提取两部分构成。前向问题模型基于静电散射理论,通过该模型可以获得前向问题的解析解。与常用的采用迭代过程的前向问题求解方法相比,采用新模型的前向问题求解速度大大提高。基于提出的前向问题模型,参数提取可以视作一个约束优化问题并采用改进的单纯形算法求解。仿真实验表明,完备参数提取算法与已有的参数或信息提取算法相比,不仅能够获得乳腺癌病灶更多的信息,并且准确度和鲁棒性更好。     

CAN总线在微电阻率扫描成像测井仪中的应用

针对微电扫描成像测井仪国内的研究现状以及存在的问题,提出了一种采用CAN总线提高仪器测速的设计方法;该设计采用DSP芯片ADSP-21992作为主控制器,利用其内置的CAN通信模块,实现了CAN总线替代原有数据遥传总线;通过两次实地的测井试验,证明采用CAN总线的微电扫描成像测井仪在特殊环境和要求下实现了快速扫描测井模式,将原仪器的测量速度提高一倍,能够稳定地完成整个测井过程,数据经分析对比真实可信,这为傲电扫描成像测井仪性能的进一步提高打下了基础.     

基于BWO的太赫兹快速扫描成像系统设计

搭建了以返波管振荡器(BWO)作为辐射源的THZ透射成像系统,该系统在VC .Net环境下,采用多线程技术集成控制锁相放大器和二维平台,实现扫描控制、信号采集、数据处理、快速成像功能,操作方便快捷,旨在为今后太赫兹无损探测等研究应用领域奠定基础.     

Pritchard 1980B型分光辐射光谱仪在彩色显像管测试中的应用研究

彩色显像管测试要碰到许多亮度和色度参数测量问题,而专用测色仪器--型号为Pritchrd 1980B的分光辐射光谱仪为彩管和彩电生产厂家提供了进行光色测量较为有效和准确的工具.本文将就其在彩色显像管测试中的应用作一探讨和研究,并提供最佳操作方法以便能帮助使用者正确地操作该仪器并能测试出精确的数据.