AMSR-E与AMSR2被动微波亮温数据交叉定标

长时间序列的对地观测数据集在研究地球环境变化及趋势分析中具有十分重要的意义。而目前的对地观测卫星寿命很少有到数十年或者几十年以上。因而,通过对具有重叠观测并且具有相近配置的传感器之间进行交叉校正获得连续的对地观测数据就显得十分必要。由于不同传感器之间系统配置以及定标过程不同等,即使同时同地的观测值也可能会有一些差异。AMSR\|E和AMSR2具有极其接近的物理配置,为了获得长时间序列的地表参数数据集,选取该传感器2013~2014年一年期18.7 GHz和36.5 GHz陆面观测数据进行对比来确定观测值之间的差异,并建立了针对两传感器在这两个频率之间基于像元观测的线性转换模型。对比发现这两个通道的观测值之间的相关性在0.98以上,两传感器同时同地亮温观测值有2~6 k的差距,这些差异在地表参数反演及长时间序列数据集的建立中应予以关注。
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Sea Ice Extent and Classification Mapping with the Moderate Resolution Imaging Spectroradiometer Airborne Simulator

An algorithm for mapping sea ice extent and generalized classification of sea ice by reflective and temperature characteristics with Moderate Resolution Imaging Spectroradiometer (MODIS) Airborne Simulator (MAS) data is presented. The algorithm was tested using a MAS scene over the Bering Sea near St. Lawrence Island, Alaska, USA, acquired 8 April 1995. Clouds were masked with the University of Wisconsin cloud masking algorithm. Ice surface temperature was estimated with a split-window technique. Sea ice extent and generalized type of sea ice were identified based on reflective characteristics and estimated ice surface temperature using a grouped criteria technique. Resulting maps were consistent with visual interpretation and with sea ice extent and type information reported in prior studies of the region.     

MODIS数据反演地表温度的传感器视角校正研究

提出了MODIS数据传感器视角的计算方法,并分析了视角的变化对大气透过率以及地表温度反演的影响。选取渤海地区一景影像进行实验研究,结果表明MODIS数据边缘的传感器视角可达55.02°,由此引起的大气透过率降低近0.086,引起的地表温度误差最高可达3.64℃。     

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．     

光扫描型pH 图象传感器测试条件的研究与分析􀀂

以LAPS为基础,研究高分辨率光扫描型二维pH图象传感器及其测量系统,重点研究了传感器的芯片材料与测试条件对传感器输出光电压的影响,并给出优化参数.在此基础上对溶液二维pH值分布进行了测量,并给出溶液pH值二维分布的灰度图.