FFT Selective and Adaptive Filtering for Removal of Systematic Noise in ETM+ Imageodesy Images

The images of imageodesy derived from Landsat-7 Enhanced Thematic Mapper Plus (ETM+) image pairs across an earthquake event exhibit severe horizontal and vertical striping noise patterns that obscure the desired information relating to earthquake-induced terrain displacements. The periodic noise patterns were analyzed to reveal that the principal cause of these errors was due to the two-way across-track scanning mechanism of the ETM+ instrument in relation to the minor shift of the satellite orbits between two acquisitions. We first focused on the design of selective filters pinpointing the noise frequencies of horizontal striping based on frequency-domain analysis, via fast Fourier transform (FFT). As a result, the horizontal striping patterns have been successfully eliminated, but meanwhile the systematic varying frequency nature of the more complicated wavy vertical striping patterns is better revealed. This has led to the successful design of an adaptive FFT frequency filtering mechanism based on the function characterizing the relationship between angular speed of a scanner imaging system and its corresponding line speed on the curved surface of the Earth. Finally, the horizontal and vertical striping patterns have been successfully eliminated by semiautomatic selective and adaptive filtering procedures without subduing the key information of coseismic displacement     

Cartographic Accuracy of LANDSAT-4 MSS And TM Image Data

Investigations of the cartographic quality of Landsat-4 MSS and TM image data in CCT-p formats have produced rectification accuracies (rmsexy values) of ± 2/3 to ± 1 data pixel for both whole and subscene areas using polynomials of the first through third degree. In order to achieve these accuracies with MSS data, 15 or more Ground Control Points (GCP's) are required, whereas with the TM data sets as few as 5-10 GCPs will suffice. Factors which limit the cartographic rectification accuracies of the Landsat-4 data include: 1) spatial resolution of the data; 2) map and digitizing errors; and 3) terrain relief. Of these factors, data resolution is the most significant, limiting the location of GCP's to about ± 0.5 pixel. Horizontal displacements due to terrain relief can be minimized by selecting GCP's at or near midrange elevations. Overall, the representative rmsexy values of ±25 and ±55 m for TM and MSS data sets are within U.S. National Map Accuracy Standards for cartographic products of 1:100 000 and 1:200 000 scale, respectively.     

Characterization of LANDSAT-4 MSS And TM Digital Image Data

Engineering analyses conducted to assess image data quality are described and results are presented for the Landsat-4 Multispectral Scanner (MSS) and Thematic Mapper (TM). Also, coincident data from the two sensors are compared. Macroscopic studies addressed trends and characteristics of full frames of data, while ?microscopic? studies assessed differences between individual detector responses. Raw data, radiometrically corrected data, and fully corrected data were analyzed, as well as special calibration data. The Landsat-4 MSS was found to produce data of high quality, comparable to previous Landsats, except for a low-level coherent noise effect which is unique to the current sensor. Radiometric relationships between Landsat-2 and -3 MSS's and the Landsat-4 MSS were established through empirical analysis of simultaneously acquired data. The TM was found to produce image data of very good spatial resolution and overall good radiometric data quality, showing improvements over MSS. Radiometric equalization of detector responses was found to be close to the theoretical limit of quantization error, except for two relatively low-amplitude artifacts. One is a difference in response that depends on the direction of mirror scan. This produces scan-angle effects superimposed on scene-related effects. The second is a tendency for level shifts to occur between mirror scans at random times but with correlations between detector responses. Two forms or patterns of level shift were identified, corresponding to four system noise states. Preliminary correction models and/or procedures have been developed and recommended for further evaluation.     

Landsat sensor performance: history and current status

The current Thematic Mapper (TM) class of Landsat sensors began with Landsat-4, which was launched in 1982. This series continued with the nearly identical sensor on Landsat-5, launched in 1984. The final sensor in the series was the Landsat-7 Enhanced Thematic Mapper Plus (ETM+), which was carried into orbit in 1999. Varying degrees of effort have been devoted to the characterization of these instruments and data over the past 22 years. Extensive short-lived efforts early in the history, very limited efforts in the middle years, and now a systematic program for continuing characterization of all three systems are apparent. Currently, both the Landsat-5 TM and the Landsat-7 ETM+ are operational and providing data. Despite 20+ years of operation, the TM on Landsat-5 is fully functional, although downlinks for the data are limited. Landsat-7 ETM+ experienced a failure of its Scan Line Corrector mechanism in May 2003. Although there are gaps in the data coverage, the data remain of equivalent quality to prefailure data. Data products have been developed to fill these gaps using other ETM+ scenes.     

Iterative satellite image segmentation by fuzzy hit-or-miss and homogeneity index

Object-based segmentation is the first essential step for image processing applications. Recently, satellite image segmentation techniques have been developed, but not enough to preserve the significant information contained in the small regions of an image. The proposed method is to partition the image into homogeneous regions by using a fuzzy hit-or-miss operator with an inherent spatial transformation, which enables the preservation of the small regions. In the algorithm proposed here, an iterative segmentation technique is formulated as consequential processes. Then, each time in iterating, hypothesis testing is used to evaluate the quality of the segmented regions with a homogeneity index. The segmentation algorithm is unsupervised and employs few parameters, most of which can be calculated from the input data. This comparative study indicates that the new iterative segmentation algorithm provides acceptable results as seen in the tested examples of synthetics and satellite images.     

基于MapX的卫星遥感影像地图导航系统设计

针对现有的无人机矢量地图导航系统图像不直观、高程数据缺失和矢量点线位置精度有限等不足,基于MapX开发平台,设计了无人机地图导航系统的结构与功能方案。对卫星遥感影像地理信息关联及海量检索处理、矢量图层与栅格图层综合显示处理等关键技术进行了研究,并利用VC++6.0工具开发了一套地形地貌直观丰富、数据处理方便可靠的无人机卫星遥感影像地图导航系统。     

实时数字引导中的数据处理

阐述了航天统一测控站在卫星和飞船发射过程中，实时数字引导中的数据处理。其中包括数据变换、数据的时间比对、外推估值等方法，提高了数字引导精度和设备的角度捕获能力。     

An Algorithm for Computing the Number of Distinct Spectral Vectors in Thematic Mapper Data

A computationally efficient method was developed to compute the number of distinct spectral vectors and their frequency of occurrence in Landsat-4 Thematic Mapper (TM) data. The algorithm first partitions the image into spectrally disjoint subsets and then computes the frequency distribution of distinct spectral vectors within each subset from a multidimensional histogram. The overall frequency distribution is tabulated by accumulating the results from each subset. The number of distinct spectral vectors could be used as a measure of potential storage compaction of alternate data representations for data compression, or as a measure of information content in the comparison of spectral band combinations and/or spatial resolutions for an image. Results from processing three 512 X 512 pixel Landsat-4 TM images and one Landsat-4 Multispectral Scanner (MSS) image are presented as examples. An algorithm for computing the frequency distribution of distinct spectral vectors in MSS data is given in the Appendix.     

The Role of Artificial Intelligence in the Integration of Remotely Sensed Data with Geographic Information Systems

Although databases for geographic information systems (GIS) have been developed to manage digital map data, the integration of remotely sensed imagery and other collateral non-map information is rarely performed. For the most part, the use of sophisticated intelligent spatial databases, in which the user can query interactively about map, terrain, or associated imagery, is unknown in the GIS and cartographic community. In standard GIS systems, the ability to formulate complex queries requiring dynamic computation of factual and geometric properties is severely limited, often reflecting its origin as collections of thematic map overlays. Spatial database research requires the integration of ideas and techniques from many disciplines such as computer graphics, computational geometry, database methodology, image analysis, photogrammetry, and artificial intelligence. In this paper we discuss some ideas on how the scope of geographic information systems can be expanded by utilizing techniques from the Al community that may remedy deficiencies in user interfaces, spatial data representation, and its utilization. We draw on ongoing research at Carnegie Mellon University for examples of these techniques in the areas of image/map database and knowledge-based image interpretation.     

Models for motion-based video indexing and retrieval

With the rapid proliferation of multimedia applications that require video data management, it is becoming more desirable to provide proper video data indexing techniques capable of representing the rich semantics in video data. In real-time applications, the need for efficient query processing is another reason for the use of such techniques. We present models that use the object motion information in order to characterize the events to allow subsequent retrieval. Algorithms for different spatiotemporal search cases in terms of spatial and temporal translation and scale invariance have been developed using various signal and image processing techniques. We have developed a prototype video search engine, PICTURESQUE (pictorial information and content transformation unified retrieval engine for spatiotemporal queries) to verify the proposed methods. Development of such technology will enable true multimedia search engines that will enable indexing and searching of the digital video data based on its true content.     

Remote sensing of land surface temperature: the directional viewingeffect

Land surface temperature and emissivity products are currently being derived from satellite and aircraft remote sensing data using a variety of techniques to correct for atmospheric effects. Implicit in the commonly employed approaches is the assumption of isotropy in directional thermal infrared exitance. The authors' theoretical analyses indicate angular variations in apparent infrared temperature will typically yield land surface temperature errors ranging from 1 to 4°C unless corrective measures are applied     

Landsat-4/5 Band 6 relative radiometry

Relative radiometric responses for the thematic mapper (TM) band 6 data from Landsat-4 and Landsat-5 were analyzed, and an algorithm has been developed that significantly reduces the striping in Band 6 images due to detector mismatch. The TM internal calibration system as originally designed includes a DC restore circuit, which acts as a feedback system designed to keep detector bias at a constant value. There is a strong indication that the DC restore circuitry implemented in Band 6 does not function as it had been designed to. It operates as designed only during a portion of the calibration interval and not at all during acquisition of scene data. This renders the data acquired during the calibration shutter interval period virtually useless for correction of the individual responses of the four detectors in Band 6. It was observed and statistically quantified that the relative response of each of the detectors to the band average is stable over the dynamic range and throughout the lifetime of the instrument. This allows an alternate approach to relative radiometric correction of TM Band 6 images     

基于FPGA的多DSP红外实时图像处理系统

多处理器系统已广泛应用于高速信号处理领域,为提高系统性能,更好地发挥多处理器优势,介绍采用基于FPGA的多DSP架构。利用FPGA作为数据调度核心,将处理器从繁杂的数据通信工作中解放出来,充分发挥了多处理器的并行工作能力,增强了系统的重构和拓展性。该系统已应用于工程实践中,以一块高密度电路板实现了从数据采集到图像校正、图像处理,以及图像显示的整个流程,能够满足对处理时间要求较高、较为复杂的图像处理算法的要求。     

基于二值化的边缘图像滤波方法

图像经过边缘提取之后常会带有各种噪声,提取的边缘还不能满足我们的需要。讨论了对边缘图像的滤波方法,先对图像进行二值化,再进行区域标记,处理后的图像再与边缘图像进行与运算。实验结果表明,该方法对提高边缘图像的质量是非常有效的,并且具有非常高的实用性。     

Revised Radiometric Calibration Technique for LANDSAT-4 Thematic Mapper Data

A technique for the radiometric correction of Landsat-4 Thematic Mapper (TM) data was proposed by the Canada Centre for Remote Sensing (CCRS) in 1982, and two reports defining the method and discussing preliminary results were presented by CCRS at the Landsat-4 Scientific Characterization Early Results Symposium [1] and [2]. Subsequent detailed observations of raw image data, raw radiometric calibration data, and background measurements extracted from the raw data stream on High Density Tape have highlighted in the proposed method, major shortcomings, which if left uncorrected, can cause severe radiometric striping in the output product. Observations presented here show that there are random fluctuations in the background level for spectral band 1 of magnitudes ranging from 2 to 3.5 digital numbers (DN), depending on detector number. Similar variability is observed in all the other reflective bands, but with smaller magnitude in the range 0.5 to 2.5 DN. More significantly, it is shown how measurements of the dc background level can be correlated with variations in both image data background and calibration samples. The effect on both raw data and on data corrected using the earlier proposed technique is explained, and the correction required for these factors as a function of individual scan line number for each detector is described. It is shown how the revised technique, which includes corrections for a line-dependent offset in addition to the scene-dependent gain and offset, can be incorporated into an operational environment.     

Radar Image Processing for Rock-Type Discrimination

Radar images have unique radiometric and geometric characteristics which present unique problems and opportunities for geological application. This paper reviews preprocessing and analytical techniques found useful or promising for applications of radar images to geologic problems such as rock-type discrimination. The use of coherent monochromatic illumination in radar images results in image speckle noise which interferes with characterization of the imaged surface. Median value filtering of the radar images removes speckle with minimal edge effects and resolution degradation. Variations in radar scene illumination due to uncompensated sensor platform motions or antenna pattern effects can be somewhat corrected for by mean and variance equalization in a direction perpendicular to the resulting image gradient. Registration of radar images to a map base and compensation of terrain induced image distortion can be accomplished by registration to digital elevation models and knowledge of imaging geometry. Analysis of SEASAT images with coregistered LANDSAT images indicates that the radar data can make a significant contribution to rock-type discrimination, especially if textural measures are incorporated. The sensitivity of radar backscatter to local slopes makes radar images an excellent medium from which to extract textural measures. Three techniques for extraction of the textural data inherent in the radar images are presented. Computation of image tone variance over various areas can numerically encode image texture. Hue-saturation-intensity split spectrum processing displays low-frequency variations in color while preserving high-frequency detail.     

基于FPGA的星载SAR成像信号处理技术

通过现场可编程门阵列(FPGA)设计并实现星载合成孔径雷达(SAR)成像处理,能够完成对多种模式星载SAR回波数据的高速处理。该文搭建的成像处理系统以子孔径极坐标格式算法(PFA)为核心,首先,在精确的多普勒中心频率估计基础上,采用基于尺度变换原理的距离向处理(PCS)与方位向高精度sinc插值级联的算法处理流程实现子孔径数据域重采样,极大地提升了处理精度与运算效率;然后,对各子孔径图像进行辐射校正消除扇贝效应,并采用加权平均算法获得了全孔径拼接图像;最后,基于Sentinel-1卫星实测数据对本系统进行了验证和分析,在系统工作频率200 MHz情况下,能够在5.92 s内实现8 192×8 192像素点的32位单精度浮点成像处理,实测数据成像结果验证了该系统的有效性,从而为实时处理奠定了技术基础。     

Satellite land mobile communication systems

The emergence of satellite land mobile services over the last 10 to 15 years is described together with future trends. The difficulties of providing a commercially viable voice service are discussed and alternatives, such as inclined orbit systems and satellites with very large antennas, are suggested as ways in which the initial disadvantages might be overcome. Data services for satellite land mobile traffic and the possibilities of including radio determination of vehicle location as part of these data services are also considered. Future systems, which could have their architecture strongly influenced by the use of onboard processing, are discussed     

Maximum cross correlation automatic satellite image navigation and attitude corrections for open-ocean image navigation

To enable "automated" image navigation (without human intervention) a base image is defined, and the maximum cross correlation (MCC) method is used to automatically compute the satellite attitude parameters required to geometrically correct images to this base image. Several levels of filters insure that contamination from cloudy pixels is minimized. The MCC method produces displacement vectors, which are translated into satellite attitude corrections to be added to the orbital image navigation corrections. The auto attitude corrections are shown to be more accurate than the traditional linear translation methods. A further application of the attitude corrections is demonstrated whereby attitude corrections computed over land can be carried forward in the satellite's orbit to accurately navigate imagery over the open ocean where no map reference points are available. Tested for two land sites well separated in a single orbit this method is shown to be as accurate as when applied to an individual image.     

双色红外信号亚成像目标识别处理系统研究

采用高速数字信号处理器(DSP)软硬件的技术途径，在双色红外制导导引头信号处理中，对由红外传感器不同波段提供的大量目标信息，进行了综合分析并提取目标特征量。应用目标识别算法，灰度直方图变换、多尺度变换、图像滤波等方法区分真假目标，建立判决理论，确立逻辑选择条件。在算法编程，实现对目标的亚成像图及目标方位信息的准确判定等方面，作了一定的研究与探讨。