Spectral noise causes distorted spectra, shifting the central wavelength and thus reducing the accuracy of surface parameter retrieval. A hybrid method combining mathematical-morphology and wavelet-transform (WB)-based filters was used to remove spectral noise. First, a generalized mathematical-morphology (GM) filter was used to remove large-amplitude noise, and then the processed spectra were smoothed using the WT-based filter to remove small-amplitude noise. The simulated noise spectrum and 76 measured canopy spectra for winter wheat were denoised with three filters: the combination filter (CF), GM, and WT. In the simulated experiments, five evaluation indices were calculated to evaluate the denoising effects. For measured spectra, qualitative analyses were performed based on spectral characteristics. Quantitative evaluations were conducted by deriving various vegetation indices from denoised spectra to retrieve wheat’s biophysical and biochemical parameters. The results indicated that the CF removed both large- and small-amplitude noise efficiently, improving signal-to-noise ratio and peak signal-to-noise ratio of simulated noise spectrum and retrieval accuracy of leaf water content (LWC) significantly. Meanwhile, it better maintained the waveform and smoothness of spectrum, improving the retrieval accuracies of leaf area index and chlorophyll data slightly. The coefficient of determination (R2) of developed model between the modified normalized difference water index and LWC was improved from 0.428 to 0.622 using the CF, 0.555 using the GM, and 0.549 using the WT. The R2 and root mean square error between the measured and retrieval LWC were improved from 0.364 and 0.027 to 0.611 and 0.018 using the CF, whereas the corresponding values were 0.504 and 0.022 for the GM, and 0.478 and 0.023 for the WT.
Hyperspectral remote sensing allows for the detailed analysis of the surface of the Earth by providing high-dimensional images with hundreds of spectral bands. Hyperspectral image classification plays a significant role in hyperspectral image analysis and has been a very active research area in the last few years. In the context of hyperspectral image classification, supervised techniques (which have achieved wide acceptance) must address a difficult task due to the unbalance between the high dimensionality of the data and the limited availability of labeled training samples in real analysis scenarios. While the collection of labeled samples is generally difficult, expensive, and time-consuming, unlabeled samples can be generated in a much easier way. Semi-supervised learning offers an effective solution that can take advantage of both unlabeled and a small amount of labeled samples. Spectral unmixing is another widely used technique in hyperspectral image analysis, developed to retrieve pure spectral components and determine their abundance fractions in mixed pixels. In this work, we propose a method to perform semi-supervised hyperspectral image classification by combining the information retrieved with spectral unmixing and classification. Two kinds of samples that are highly mixed in nature are automatically selected, aiming at finding the most informative unlabeled samples. One kind is given by the samples minimizing the distance between the first two most probable classes by calculating the difference between the two highest abundances. Another kind is given by the samples minimizing the distance between the most probable class and the least probable class, obtained by calculating the difference between the highest and lowest abundances. The effectiveness of the proposed method is evaluated using a real hyperspectral data set collected by the airborne visible infrared imaging spectrometer (AVIRIS) over the Indian Pines region in Northwestern Indiana. In the paper, techniques for efficient implementation of the considered technique in high performance computing architectures are also discussed.
Minerals are generally present as intimate mixtures. The spectra of intimate mixtures in visible-infrared are complex function of abundance, grain size, and optical constants et.al, making the linear spectral unmixing model inapplicable. In this paper, we presented a nonlinear unmixing method by combining Shkuratov model (SK99) and Hapke model (H81) to unmix the mineral mixtures. For obtaining the abundances of mineral endmembers, we built up a look-up table (LUT) in the following steps: First, the optical constants were derived by SK99 model and then single scattering albedos of endmembers were computed. Second, the approximation of multiple scattering was derived by the Chandrasekhar H-function. Finally, LUT was established using H81 model. The root-mean-square error (RMSE) was calculated to find the best match between the reflectance of mixtures and LUT. We used the laboratory mineral mixtures to verify the accuracy of abundance estimation. The results show that RMSEs are less than 1% and the absolute errors of abundance retrieval are within 5%. The presented method can retrieve mineral abundance effectively and rapidly. It can be a potential method applying for hyperspectral images of the earth and planetary.
Non-negative matrix factorization (NMF) has been introduced into the field of hyperspectral unmixing in the last ten years. Though NMF-based approaches have been widely accepted by researchers, the assumptions in them may not always fit for the characteristics of real ground objectives, which will cause the incorrect results and restrict the applications for these approaches. This paper proposes a novel semi-supervised NMF model, in which the ground truth information is introduced such as partial known endmembers from ground measurment. The relationship between the known and unknown endmembers are explored. The distance function is designed to describe the relationship and introduced into the NMF model. In this way, SSNMF could use the known endmembers to help estimating the unknown endmembers, so that accurate and robust results can be obtained. The proposed algorithm was compared with NMFupk, which also considered partial known endmembers, using extensive synthetic data and real hyperspectral data. The experiments show that the proposed algorithm can give a better performance.
The vegetation index (VI) and vegetation water index (VIw) have long been used for plant water stress
detection indiscriminately, without considering the effects of differences in their band selection. To address
this, this study quantitatively compared the difference of sensor dependence for the two indices based on
canopy/atmospheric radiative transfer model. Five different bandwidths at canopy and top-of-atmosphere scale
were simulated separately for 23 classic indices. The results show that VIws exhibited better correlation with
vegetation water content (VWC) at both scale ( R2 : 0.835; 0.812) in comparison with VIs ( R2 : 0.474; 0.475). To
quantitatively describe the uncertainty caused by bandwidth, a new index variability was established. VIws and
VIs performed entirely differently: at canopy scale, the uncertainty caused by bandwidths for VIws and VIs is
13.703% and 43.451%, respectively. However, at top-of-atmosphere scale, the uncertainty for VIws and VIs is
32.021% and 41.265%. VIws exhibited less dependence on bandwidth and were more affected by atmospheric
effect than VIs. We attribute these differences to differences in band selection: VIws based on water absorption
features are more sensitive to not only variation of VWC but also atmospheric conditions. Conversely, as
chlorophyll absorption features which VIs are calculated on effectively avoid atmospheric absorption features
and are located in red edge region, VIs are found less affected by the atmosphere condition and extremely
sensitive to bandwidth. Results figure out the differences we should focus on when we choose VI or VIw from
different sensors for VWC retrieval.
Coverage rates of vegetation and exposed bedrock are two key indicators of karst rocky desertification (KRD) envionmnents. Based on spectral unmixing algorithm, abundance of vegetation and exposed rock were retrieved from the hyperspectral Hyperion image. They were verified by the spectral indices of Karst rocky desertification (SIRD) and vegetation chlorophyll index. It showed that the abundance had significant linear correlation with SIRD. The determinate coefficients (R2) were 0.93,0.66, 0.84 for vegetation, soil and rock respectively, indicating that the abundances of vegetation and bedrock can characterize their coverage rates to a certain extent. Then, the abundances of vegetation and bedrock were graded and integrated together to evaluate the rocky desertification in typical Karst region. This study implies that spectral unmixing algorithm based on hyperspectral remote sensing image will have potential use in monitoring and evaluating KRD.
Hyperspectral data offers a powerful tool for predicting soil heavy metal contamination due to its high spectral resolution
and many continuous bands. However, band selection is the prerequisite to accurately invert and predict soil heavy metal
concentration by hyperspectral data. In this paper, 181 soil samples were collected from the suburb of Nanjing City, and
their reflectance spectra and soil lead concentrations were measured in the laboratory. Based on these dataset, we
compare Least Angle Regression, which is a modest forward choose method, and least squares regression and partial
least squares regression based on genetic algorithm. As a result, regression with band selection has better accuracy than
those without band selection. Although both Least Angle Regression and partial least squares regression with genetic
algorithm can reach 70% training accuracy, the latter based on genetic algorithm is better, because it can reach a larger
solution space. At last, we conclude that partial least squares regression is a good choice for the soil lead content retrieval
by hyperspectral remote sensing data, and genetic algorithm can improve the retrieval by band selection promisingly.
Bands centered around 838nm,1930nm and 2148nm are sensitive for soil lead content.
KEYWORDS: Information fusion, Chemical elements, Associative arrays, Standards development, Data modeling, Roads, Remote sensing, Geographic information systems, Artificial intelligence, Telecommunications
Metadata is important to facilitate data sharing among Geospatial Information Communities in distributed environment. For unanimous understanding and standard production of metadata annotations, metadata specifications are documented such as Geographic Information Metadata Standard (ISO19115-2003), the Content Standard for Digital Geospatial Metadata (CSDGM), and so on. Though these specifications provide frameworks for description of geographic data, there are two problems which embarrass sufficiently data sharing. One problem is that specifications are lack of domainspecific semantics. Another problem is that specifications can not always solve semantic heterogeneities. To solve the former problem, an ontology-based geographic information metadata extension framework is proposed which can incorporate domain-specific semantics. Besides, for solving the later problem, metadata integration mechanism based on
the proposed extension is studied. In this paper, integration of metadata is realized through integration of ontologies. So
integration of ontologies is also discussed. By ontology-based geographic information semantic metadata integration,
sharing of geographic data is realized more efficiently.
Aerosol model is a major obstacle for passive remote sensing of aerosol properties. For the continent or urban aerosol
model does not fit the needs for more accurate retrieval, and the user defined aerosol model may be more near to the
realistic condition in Taihu region. A method has been developed for retrieving the aerosol model and optical properties
including polarization, i.e., scattering coefficient, asymmetry factor, single scattering albedo, scattering phase function
and polar phase function. In Lake Taihu, the study area of our two combined remote sensing observations in the winter and summer 2006, we got water surface spectral data of ASD (Analytical Spectral Devices) by the ship, atmospheric data of CE318 sunphotometer on the shore, and the MODIS (Moderate Resolution Imaging Spcectroradiometer) image data on the TERRA Satellite. By using the nearly synchronous measurements of the data from surface spectrum and the sunphotometer with the image, and by use of the radiative transfer model 6S(Second Simulation of a Satellite Signal in the Solar Spectrum), varying the components of the aerosol type, a LUT (look up table) is made for the radiance on the satellite. When the total relative error of the new defined parameter for relative error is getting to the least, the aerosol type will be decided. Then, based on the determination of aerosol model, the atmospheric aerosol properties over Lake Taihu have been computed by using Mie theory and analyzed with the typical continental and urban aerosol models available in 6S. These results show that the user-defined aerosol model is a mix model of continent and urban which corresponds with previous studies. Moreover, they may be useful for resolving the vector RTE (radiative transfer equation). In this paper we tried to provide a method with the combination of remote sensing data to obtain the optical properties of atmospheric aerosol over inland water in different seasons. We respect it will be helpful for accurate atmospheric correction in the future.
Estimates of vegetation water content are of great interest for assessing vegetation water status in agriculture and forestry, and have been used for drought assessment. This study focuses on the retrieval of foliar water content with hyperspectral data at canopy level. The hyperspectral image used in this study was acquired by the airborne operative modular imaging spectrometer (OMIS) at Demonstration Site for Precision Agriculture in Xiaotangshan area, Beijing, on April 26th, 2001. 40 image spectra were extracted to correspond to the quasi-synchronous meansurements of foliar water content (FWC). The image spectra of winter wheat were utilized to validate the sensitivity of the existing and novel water indices and parameters of three water absorption features in NIR and SWIR regions. Correlation analysis showed that, NDWI(860,1241) and NDWI(860,1200) both had significant linear relationships with FWC (R2 were 0.4124 and 0.4042 respectively). Red edge position (REP) could reflect indirectly the variations of wheat FWC to some extent. Significant linear relationships were also found between WI(820,1600) and FWC, and between WI(900,1200) and FWC, while no relationship was shown between the traditional WI(900,970) and FWC. The derived depth of water absorption centered around 2078nm, namely AD2078, had the highest linear correlation with FWC (R2 is 0.4551) , much higher than those parameters derived from the two water absorption around 1175 and 1409. In the end, AD2078 was applied to OMIS image to map the foliar water content. The value range of the inverted foliar water content ranged from 69.39 to 78.35%, which was quite close to that of the field measurements (70.72-78.12%). The distribution of the FWC map was quite consistent with growth status of winter wheat.
Nowadays, huge volumes of geospatial data and services are available and accessible to people all over the world.
However, they are searched mostly based on keyword, which is inherently restricted by the ambiguities of natural
language, which can lead to low precision and recall. In this paper, semantic share of geospatial data and services are
studied based on ebXML registry. But ebXML registry specification doesn't take into account the registration of the
semantic information. So we define how OWL DL constructs are mapped to ebXML registry information model
(ebRIM) constructs without causing any changes in the core ebXML registry specification. After that, predefined stored
procedures are provided in the ebXML registry for semantic search, which provide necessary means to exploit the
enhanced semantics stored in the Registry. Then, geospatial ontologies in change detection application of remote sensing
based on Global Change Master Directory, ISO19119 and ISO19115 are established. Finally, a prototype system is
developed based on an open source-ebxmlrr to demonstrate the proposed model and approach.
KEYWORDS: Geographic information systems, Taxonomy, Web services, Data conversion, Composites, Network security, Process modeling, Roads, Data processing, Spatial analysis
The Combination of Geographic Information Services (GIServices) is studied in this paper. First, the way of GIServices combination is analyzed. Based on GIServices combination ways depicted by Service-Oriented Architecture (SOA), OpenGIS (OGC) Web Services Architecture and International Organization for Standardization (ISO) 19119, GIServices combinations are classified into Discrete Service Combination, Chaining Service Combination and Hybrid Service Combination in this paper. Then, the model of GIServices combination is focused. A high-level GIServices combination model based on Petri Net is proposed to improve those proposed by former researchers. The proposed high-level model can represent services combination relationship more clearly and can help to control services combination behavior in an easier way. Since searching GIService that can accomplish certain GIS task is a key step of implementing GIServices combination, GIServices taxonomy is then studied. A multi-level task-oriented GIServices taxonomy is proposed in this paper. Correspondence between GIS tasks and GIServices can be established more easily with the proposed multi-level task-oriented GIServices taxonomy. Finally, a case study is made to support the proposed theories.
A fractal-based image compression algorithm under wavelet transformation for hyper-spectral remote sensing image was introduced in this paper (also named AWFC algorithm). With the development of the hyperspectral remote sensing we have to obtain more and more spectral bands and how to store and transmit the huge data measured by TB bits level becomes a disaster to the limited electrical bandwidth. It is important to compress the huge hyperspectral image data acquired by hyperspectral sensor such as MODIS, PHI, OMIS etc. Otherwise, conventional lossless compression algorithm couldn't reach satisfied compression ratio while other loss compression methods could get results of high compression ratio but no good image fidelity especially to the hyperspectral image data. As the third generation image compression algorithm-fractal image compression is superior than traditional compression methods with high compression ratio, good image fidelity and less time complexity. In order to keep the spectral dimension invariability, we have compared the results of two compression algorithms based on the outside storage file structure of BSQ and BIP separately. The HV and Quad-tree partitioning and the domain-range matching algorithms have also been improved to accelerate the encode/decode efficiency. The proposed method has been realized and obtained perfect experimental results. At last, the possible modifications algorithm and the limitations of the method are also analyzed and discussed in this paper.
Atmospheric correction based on hyperspectral image itself was performed on the new spaceborne imaging spectrometer CHRIS image by using the popular radiance transfer code ACORN(Atmospheric CORrection Now) and empirical algorithm as well, in this way, the calibration performance of CHRIS was evaluated by the retrieved spectra of vegetation and soil. It turned out, the vegetation reflectance spectra inverted by ACORN could characterize vegetation reflectance in the range of 498~760nm, but gave a fairly large deviation beyond 760nm, showing the deficiency of spectral calibration beyond 760nm. The ACORN derived soil reflectance decreased after 760nm, which is quite inconsistent with common sense, showing that the calibration accuracy couldn't meet requirements of ACORN for spectral and radiometric calibration at certain spectral range. In addition, the stripes on the retrieved water vapor content map indicated that the radiance calibration performance needs to be improved. On the contrary, AVIRIS was validated to have better calibration performance so that more precise spectra could be retrieved by ACORN5.
To meet the demand of monitoring water pollution in China, Information Center of State Environmental Protection of China (ICSEP) and Institute of Remote Sensing Applications, Chinese Academy of Sciences (IRSA,CAS) have carried out a project to utilize the data extracted from Environment and Hazard Monitoring Constellation. This project is to build the first Remote-sensing and Environmental Monitoring System (REMS) in China. The most important component of REMS is the Hyperspectral-Environmental Database (HED). This paper is to describe the architecture and mechanism of HED. HED consists of five parts: Environmental backgrounds, Spectrums, Hyperspectral images, Basic geographic information and Environmental quality data. The interactions and relationships among the five parts are depicted. The workflow of HED assisting REMS is delineated. A preliminary research in Taihu Lake based on HED is also described in this paper.
KEYWORDS: Databases, Data mining, Analytical research, Remote sensing, Biological research, Mining, Relativity, Data conversion, Data processing, Data integration
Remote sensing data, especially the hyperspectral remote sensing data, characterize their great quantities. So how to deal wtih these data is a focus. Database has solved the problem of storing, searching, updating and maintaining of the data, but it is not satisfactory in disposing them. In recent years, the technology of data warehouse has great development. It can re-integrate, synthesize and separate the data of database, and use the searching pattern of multiple dimensions to realize data mining (DM). This technolgoy has been widely used in commerce to analyze the inner relationship of the numerous data and makes some remarkable achievements in decision supporting. Data warehouse and Data mining technology have been used in GIS. This article would give a set of complete steps and some general methods in using the DM to analyze the remote sensing data, especially in hyperspectral data. And it tries to do some preliminary exploration in using it to deeply analyze the potential relations among the acquired spectra, images and biology parameters of the experiments and get some anticipated possible results.
In some complicated terrain area, such a loess plateau of China, it is very difficult to get higher accuracy of landuse classification only depending on the traditional spectral statistics methods, especially the image pixel size is much larger than the geomorphology units. In order to improve the image classification results, large scale relief map has been used to create the digital geomorphology model(DGM). DGM can be used to do the pixel unmixing works, specially reducing the influence of terrain shadow. Applying fuzzy mathematics theory, the DGM has been used to correct the digital image classification result, so as to create more accurate landuse map. In addition, this method is also helpful to find some minor objects in low spatial resolution images.
Image spectra calibration is of great importance for further processing and feature extraction. In this paper, an automated flat field reflectance calibration algorithm (AFFT) is proposed. This algorithm is an improvement to the traditional flat field transformation calibration. It is based on the fact that the so-called flat field is a flat block of high brightness and relative flat spectral response, and at a certain wavelength range (.e.g. 500-700nm) the brightness or radiance of the flat field is a certain multiple of the average spectrum of the image. Because the average image spectrum spectrum usuall is relatively flat, so a certain multiple of the average spectrum can be regarded as the criterion (or threshold) to select flat field pixels. So such parameters as wavelength range, multiple increment between flat field and the average image spectrum and number of the largest area block are set to determine the useful flat field so that an average spectrum of the flat field is obtained. By using this flat field spectrum as solar/atmospheric response, hyperspectral image can be calibrated to reflectance image. In the end, AFFT was validated by one PHI image acquired in Japan, 2000. It turns out that AFFT is effective to search all the flat fields which meet the fixed terms automatically and promptly, the spectra transformed by this method are much smoother and reliable to some extent.
The hyperspectral image used in this study was acquired by the airborne operative modular imaging spectrometer (OMIS) in Xiaotangshan area, Beijing, on April 26th, 2001. Accurate geometry correction and reflectance transformation was conducted on this image so that 43 image spectra were extracted to match with the canopy-level total nitrogen concentration (TN) of wheat precisely. By using methods of stepwise regression and spectrum feature analysis, characteristic bands and parameters were selected and developed for TN retrieval from the image spectra. Nitrogen distribution map was obtained by applying the best estimation equation to all wheat pixels. It turned out, the absorption depths and areas within spectral ranges 590-756nm,1096-1295nm and 1295-1642nm could be used to estimate TN. NDVI(NRCA1175.8,NRCA733.9) and NDVI(dr745,dr699.2) was the best estimator of TN (R2 = 0.8145 and 0.769 respectively). In addition, the value and distribution of TN map was quite consistent with the field measurements and growth status.
Usually the spectral unmixing and endmember extraction were based on the spectral statistics algorithm. In this paper, spatial knowledge, such as field patch information, was involved in the pure pixel selecting. In this way, endmember extraction was not only carried out in spectral space but also considering the spatial location of pixels. In addition, these known background information can also improve the accuracy of image classification, and also can be used to
intellectually separate pixels and evaluate each sub-pixels different attributes.
Crop physiology analysis and growth monitoring are important elements for precision agriculture management. Remote sensing technology supplies us more selections and available spaces in this dynamic change study by producing images of different spatial, spectral and temporal resolutions. Especially, the remote sensing data of high spectral and high temporal resolution will play a key role in land cover studies at national, regional and global scales. In this paper, Multi-temporal Index Image Cube (MIIC) is proposed, which is an effective data structure for the parameterization of multi-dimensions spectral curve. MIIC is very useful for supporting the dynamic analysis on vegetation phenological and physiological characters. Based on multi-temporal meteorological satellite data and multi-temporal ground spectral measurement data, the temporal characters of different vegetation physiological parameters are contrasted and analyzed from temporal index image cube. In addition, MIIC also has very wide use in hyperspectral remote sensing applications.
According to the advanced feature of hyperspectral image and Correlation Simulating Analysis Model (CSAM), a new simple but efficient kernel-adaptive filter (SRSSHF) especially for hyperspectral image is suggested in this paper. It is achieved not based on the traditional sigma (standard deviation) statistics in spatial dimension, but on the valid-pixel judge in spectral dimension and the intellectualized shift convolution in spatial dimensions. So its criteria is based on the intrinsic property of objects by adequately utilizing the spectral information that hyperspectral affords. Such a filter also is an adaptive filter, and its kernel size theoretically has no strong influence on the filter results. What it concentrates is the feature of signal itself but not the speckle noise, its criterion is in spectral dimension, and multiple iteration is available. So the tradeoff of spatial texture is not necessary. It is applied to filter and improve quality of PHI hyperspectral images acquired both in Changzhou, China and Nagano, Japan, and a >200 looks iteration and a comparison with other typical adaptive filters also are tried. It shows that SRSSHF can smooth whole the internal of a homogeneous area while ideally keep and, as well as, enhance the edges well. As good results are achieved, this paper suggests that SRSSHF on the base of CSAM is a relative ideal filter for HRS images. Some other features of SRSSHF are also discussed in this paper.
Some new vegetation models for hyperspectral remote sensing are provided in this paper. They are Derivative Spectral Model (DSM), Multi-temporal Index Image Cube Model (MIIC), Hybrid Decision Tree Model (HDT) and Correlation Simulating Analysis Model (CSAM). All models are developed and used to process the images acquired by Airborne Pushbroom Hyperspectral Imager (PHI) in Changzhou area, China, 1999. Some successful applications are provided and evaluated. The results show that DSM has the ability of eliminating the background interference of vegetation analysis. MIIC is a viable method for monitoring dynamic change of land cover and vegetation growth stages. HDT is effective in precise classification of rice land while CSAM provide a possibility and theoretical basis for crop identification, breed classification, and land information extraction especially for rice.
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