最新刊期
卷 14 ， 期 2 ， 2010
- 摘要：Radiometric calibration is the key of improving quality and quantitative applications of the remote sense data. A irradiance-based radiometric calibration campaign was performed by National Spaceborne Demonstration at the Erenhot test site on June 1, 2007, in which Terra MODIS was the object. It showed that the irradiance-based calibration results were in good agreement with both the MODIS on-board calibration and reflectance-based calibration results with the variations less than 3.3% at the site. It was concluded that the irradiance-based calibration method was performed correctly, while the differences among the coefficients showed that the measurement of the ratio of diffuse-to-global ratio has crucial impact on results of irradiance-based calibration. The results from different aerosol modes confirmed that the irradiance-based radiometric calibration can reduce the error caused by the assumption of the aerosol mode.关键词：radiometric calibration;calibration coefficient;irradiance-based method;MODIS
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发布时间：2021-06-10 - 摘要：Multipath not only degrades the sensitivity of a GPS receiver, but also becomes the dominant error resource in GPS positioning systems. Multipath mitigation algorithm is the most significant in high sensitive and high accuracy GPS receivers. In this paper, multipath signal model in code tracking loop is studied first and a novel method for mitigation of multipath is presented which employs adaptive filtering recursive least square （RLS） algorithm. The system parameters need not be estimated in adaptive filtering algorithm and multipath signal can be filtered out directly. Under noisy scenario, the RLS algorithm is the best estimate for the filter weights with minimum least-squares errors. Simulation results show that the proposed method can reduce multipath error envelope effectively. The crossing-zero bias of the discriminator can be corrected which enhances the accuracy of code tracking in GPS receiver’s delay-locked loop （DLL）. The most importance is that the RLS algorithm is recursive and convenient to implement both in hardware and software.关键词：GPS;multipath;tracking loop;adaptive filter;error envelope
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发布时间：2021-06-10 - 摘要：The fractions of four components （sunlit leaves, shaded leaves, sunlit soil and shaded soil） and gap fraction are characteristic geometric parameters of canopy’s structure, and have great influence on radiative transfer of the vegetation. In this paper, POV-ray software was introduced to efficiently and accurately calculate the four components’ fractions and gap fraction of three-dimensional （3D） canopies. With the good agreements of computed four components’ fractions and gap fraction be- tween POV-ray and Radiosity-Graphics combined Model （RGM） based on the same 3D canopy structure, more 3D structures generated by the Clumped Architecture Model of Plants （CLAMP） model were used to study the characteristics of four compo- nents’ fractions and gap fraction. The key parameters of CLAMP model include sowing scheme, clumping index, average leaf angle （ALA） and leaf area index （LAI）. By analyzing the sensitivity of these parameters to four components’ fractions and gap fraction, the changing features of four components’ fractions and gap fraction were found. The results show that: clumping index can effectively control the spatial distribution of leaves, which affects the relative proportion of vegetation and soil in the scene. Therefore, clumping index has a great impact on the distribution pattern of four components’ fractions and gap fraction. Average leaf angle influences the anisotropy of the results. When the average leaf angle is larger, the magnitude of anisotropy is higher. Compared with other parameters, the impact of row effect on the four components’ fractions and gap fraction is primary when the scene’s row structure is obvious. Therefore, when the canopy is in a row structure, the characteristic change of four components’ fractions and gap fraction is more complex than that of homogeneous canopy. At the same time, the results of row canopy in three typical growing stages were compared, which shows that soil has a higher contribution to the four components’ fractions and gap fraction than that of vegetation at the early stage. With the increase of leaf area index, the influence of vegetation on the result is gradually enhanced and the fraction of sunlit leaves shows more apparent anisotropy. The research of this paper shows that POV-ray is a powerful tool to quantitatively study vegetation by remote sensing technology, and has potential of wider applications.关键词：POV-ray;CLAMP model;four components’ fractions;gap fraction
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发布时间：2021-06-10 - 摘要：In this paper, new synthetic aperture radar （SAR） image target recognition approach based on multiple views decision fusion is presented. Image chips are represented as feature vectors by 2-D wavelet transformation and principal component analysis algorithm. The feature vectors are classified by using algorithms of support vector machine （SVM）. After multiple views of the same vehicle collected at different aspects classified by SVM, the outputs are then fused using Bayesian approach and the final classification decision is generated. Experiments are implemented with three class targets in Moving and Stationary Target Acquisition and Recognition （MSTAR） Program database. Experimental results indicate that there are significant target recognition performance benefits in the probability of correct classification when three or more views are used for decision fusion. Therefore, the approach proposed is an effective method for SAR image target recognition.关键词：synthetic aperture radar （SAR）;target recognition;multiple views;decision fusion;Bayesian
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发布时间：2021-06-10 - 摘要：The signal processing in the bistatic SAR case is more complex than the monostatic synthetic aperture radar （SAR） case due to issues such as the range history of the target echo signal, time synchronization error, time-varying Doppler rate because of squint, etc. In this paper, a monostatic equivalent geometry model of bistatic SAR is established; the mechanism of the System time synchronization error is analyzed; a time synchronization error correction method based on direct-path signal is presented; a modified time-varying step transform algorithm is used for bistatic SAR. Theoretical analysis and experimental data processing confirmed the effectiveness of the algorithm.关键词：bistatic;synthetic aperture radar;time synchronization;imaging algorithm
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发布时间：2021-06-10 - 摘要：Highly accurate geometric correction is fundamental to the application of satellite images. In highly accurate geo- metric correction of remote sensing images for precise match to the base maps, the difficulties in capturing ground control points （GCPs）, insufficient number of GCPs and low accuracy of the geo-referenced images remain to be frequent issues. In search for solutions to these issues, this paper proposes a new method for the geometric correction of satellite images for the mountain ar- eas based on the terrain feature lines extracted from the Digital Elevation Model （DEM）. This method uses DEM as the base maps without any geometric distortion for the geometric correction of satellite images. This paper presents the theories and method to extract terrain feature lines, such as gorges, mountain ridges, peaks and concaves and describes the procedures for the geometric correction for satellite images of mountain areas based on the terrain feature lines. It further discusses the problems in extracting terrain feature lines and capturing of GCPs, as well as the solutions to these issues. The outcome from the experiments shows the number of terrain feature lines of mountains areas are a great many times of those in the conventional map layers of hydrological systems and road networks, and that terrain feature lines extracted from DEM present high stability and reliability and can be applied in the highly accurate geometric correction for satellite images of mountain areas. The results of statistical test show the average geometric error is reduced to the size of one pixel when this method is used in geometric correction.关键词：terrain feature lines;Satellite image;highly accurate geometric correction
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发布时间：2021-06-10 - 摘要：In recent years, the green tide caused by enteromorpha prolifera bloom with fast growth rates became one of the ecological disasters. In the monitoring of Qingdao enteromorpha prolifera bloom disaster using remote sensing technology, the Multi-mode Airborne Digital Camera （MADC） system played an important role in the algae reducing planning. It provided the data source for the quick extraction of enteromorpha prolifera information. The enteromorpha prolifera monitoring results, such as the distribution, area and density, were provided to the government in time for decision. In this paper, the components and characters of MADC system are introduced, and the quick extraction technology and work flow are set up based on the analysis of the spectral and image features. The key technologies in the data process and information extraction are studied and the final remote sensing monitoring results are introduced. The feasibility of prospect application in marine disaster monitoring such as the red ride monitoring of MADC system and advices for the improvement of MADC are introduced at last. The information ex- traction method will play an important role in the marine environment monitoring especially in the contingency environment disaster monitoring.关键词：MADC;enteromorpha prolifera bloom;remote sensing monitoring;information extraction
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发布时间：2021-06-10 - 摘要：MODIS Collection 005（MODISC005） aerosol product is validated over the China Sea. Aerosol optical thickness at 550nm （AOT550） and fine mode fraction （FMF） are used to analyze spatial-temporal distribution of aerosol over the China Sea. Then meteorological data are used to discuss formation mechanism of aerosol characteristics. The results show that firstly MODISC005 aerosol product has a good quality over the China Sea. Secondly, AOT550 and FMF have a notable spatial-temporal distribution feature. AOT550 reaches maximum in spring and winter, and minimum in summer and fall; oppositely, FMF reaches maximum in summer and fall, and minimum in spring and winter. Meanwhile, AOT550 and FMF have marked longitudinal variation. AOT550 appears maximum between 30°N—40°N and decreases towards north and south. And FMF increases from south to north and the tendency of increase becomes slow at 30°N. In addition, they have an obvious meridional variation. AOT550 and FMF both decrease with the increase of longitude. Finally, based on meteorological data, the source is the continent aerosol and wind and rainfall are the two most important factors.关键词：China Sea;aerosol;spatial-temporal distribution;formation mechanism
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发布时间：2021-06-10 - 摘要：The absorption coefficient of water color constituents is an inherent optical parameter. It is the main factor which influences the distribution of the water optical field, and plays a very important role in the researches of water optics remote sensing. This paper analyses the absorption coefficient characteristics for particle matter, phytoplankton and colored dissolved organic matter（CDOM）, using the absorption coefficient of water color constituents in situ measured at the Three Gorges Dam in April, 2007. The results show that, for the Three Gorges Dam water: （1） the absorption spectrum of non-algal particles is similar with that of total particle matter; （2） the absorption coefficient of non-algal particles decreases power exponentially from short to long wavelength, and the absorption coefficient in different bands has a definite relationship; （3） the absorption coefficient of phytoplankton has a better polynomial relationship with chlorophyll a concentration in the Three Gorges Dam water; （4） piece- wise function can express the absorption coefficient characteristics of CDOM. The absorption spectrum below 500nm decreases power exponentially from short to long wavelength, and the precision of the fitting R2approaches to 1; the absorption spectrum between 501 and 700nm fits well using polynomial relationship, and the precision R2 is above 95%.关键词：Three Gorges Dam;absorption coefficient;particle matter;phytoplankton;colored dissolved organic matter （CDOM）
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发布时间：2021-06-10 - 摘要：Information of houses collapsed by the earthquake is one of the important indicators to assess the earthquake dam- age intensity, and support the emergency decision-making process in rescue and recovery operations. We monitored the house collapse ratio and its spatial variation in the 5.12 Wenchuan earthquake by airborne images, and analyzed its spatial variation relationship with the earthquake intensity, geological structure, stratum lithology and surface rupture caused by the earthquake. The house collapse ratio was derived by visually interpreting ADS40 airborne images acquired from May 15 to May 28, 2008. The results show that the houses were widely damaged in the earthquake-damaged region, especially in Wenchuan County, Mianzhu City, Shifang City, and Pengzhou City and Wenchuan County which experienced the severest damage. We analyzed the spatial variation of the house collapse ratio and its relationship with earthquake intensity, geological structure, stratum lithology and surface rupture caused by earthquake. The results demonstrate that the house collapse ratio and the earthquake intensity have positive relationship, and the ratio of house collapse is controlled by the geological structure, stratum lithology, and building structure too. The house collapse ratios, which are above 50%, mainly distributed along the surface rupture in a SW to NE direction.关键词：Wenchuan earthquake;airborne images;house collapse;earthquake intensity;surface rupture
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发布时间：2021-06-10 - 摘要：Urban internal function and structure which is represented by intra-urban land use information is important spa- tial-explicitly information in urban geography research and urban planning or management; however, its extraction of fine-scale spatial information is still a difficult question in geographic information science （GIS）. To overcome the difficulty in detecting intra-urban land use types using remotely sensed data alone and the positioning errors of mismatch in overlaying multi-temporal images, we have developed a digital reconstructing method to classify and detect intra-urban land use change through combining the "hierarchical classification" and "object-oriented segmentation" methods. This paper traces back to the historical developing process of Changchun city based on the above methods to classify and detect the detail intra-urban land use types including residential land, commercial land, industrial land, roads, water body and urban green space. The study has resolved the key problems on accurate spatial positioning from multi-scale and different data sources, classifying intra-urban land from function characteristics and detecting historical developing process of metropolis. Furthermore, we combined the SPOT5 imagery, 1:10000 topographic maps, historical maps, urban planning map and other auxiliary data of Changchun City to classify and detect its intra-urban land use change from 1905 to 2003. The results indicate that the methods are significant and effective in classifying and detecting urban land use spatial information through combining the human-computer interactive interpretation with the expert-based knowledge from different source data. The methods can not only enhance the accuracy of urban land use classification, but also improve spatial information extraction efficiency and positioning accuracy of multi-temporal spatial overlaying analysis.
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发布时间：2021-06-10 - 摘要：Light-use efficiency （LUE） is a critical parameter in many primary production models for estimating ecosystem carbon exchange. The application of these models on regional and global scale is restricted because of the difficulty of retrieving LUE from airborne and satellite remote sensing images. Vegetation chlorophyll fluorescence is a direct indicator of plant physiology. In this paper, a diurnal experiment was carried on maize on July 5, 2008. The canopy radiance spectra and tower-based flux data were acquired synchronously to test the possibility of retrieving LUE by the solar-induced vegetation ChlF signals. The canopy net primary production （NEP） values were calculated using eddy covariance measurement by a CSAT3-Li7500 Flux system, and the gross primary production （GPP） was also calculated by adding the simulated day time respiration. Two kinds of LUE based on GPP （LUEGPP） and NEP （LUENEP） were defined by dividing the absorbed photosynthetic active radiation （APAR）. The ChlF signals at 760nm and 688nm were also separated from the reflected radiance spectra based on Fraunhofer line depth algorithm in the two oxygen absorption bands. The ChlF signals were strongly correlated with photosynthetic active radiation （PAR）, especially the ChlF at 760nm （R2>0.99）. Both NEP and GPP had a significant correlation with ChlF. Furthermore, LUEGPP was negatively correlated with the ChlF’s relative intensity at 688nm and 760nm, with a correlation coefficient R2 of 0.6331 and 0.7861 respectively. Moreover, the LUE models based on the solar-induced vegetation ChlF signals were compared to some popular vegetation Indices （VIs） from the canopy reflected spectra. Canopy LUEGPP was proved able to be estimated from the remotely sensed ChlF signals.关键词：Spectra;chlorophyll fluorescence;light-use efficiency （LUE）;primary production
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发布时间：2021-06-10 - 摘要：Over the past decade wireless sensor network has become a rapidly expanding technology that has strong applications. It is regarded as an extension of traditional remote sensing technology. In this paper, a review is presented on some recent development in wireless sensor networks during the past 2—3 years and the progress on their applications to various environmental fields including global change and ecological studies, soil conditions, air quality, water quality and hydrological and marine studies, precision agriculture and target tracking. The primary challenges encountered in the development and applications of wireless sensor networks have been summarized. Some future research priorities on the application of this technology have been suggested.关键词：ecological sensors;environmental monitoring;wireless communication;global change
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发布时间：2021-06-10 - 摘要：To remove vegetation effect in soil moisture retrieval by passive microwave technique at lower frequencies, the τ-ω model is often used. In order to evaluate the scattering and attenuation characteristics of vegetation at higher frequencies, a Matrix-Doubling microwave emission model based on ray-tracing technique was used on corn, to study its single scattering albedo and transmissivity with different height at C （6.925GHz）, X （10.65GHz） and Ku （18.7GHz） bands. The comparison between simulation results and the data collected by a truck-mounted microwave radiometer in a field experiment are good. To verify the simulated emission from corn layer only, the ground surface of corn field was placed with an Aluminum foil, so as to mask the emission from the soil. A Brightness Temperature database was setup by assigning a variety of parameters to the verified model, to simulate Brightness Temperature of natural corn field with different height. The results by the Matrix-Doubling model were then matched with those by τ-ω model at the same condition by least-square deviation, so as to retrieve the effective single scattering albedo and transmissivity of corn at C, X and Ku-band.关键词：Matrix-Doubling;microwave emission;single scattering albedo;τ-ω model
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发布时间：2021-06-10
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