最新刊期
卷 23 ， 期 2 ， 2019
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摘要：In recent years, a new generation of stationary meteorological satellites in various countries has adopted the three-axis stabilized mode of operation to scan the Earth for further improvement of observation frequency and signal–noise ratio. Image registration and navigation problems must be solved to accurately extract quantitative parameters of the Earth’s surface, clouds, and atmosphere at remote sensing target locations. Orbital drift movement is one of the main causes of satellite line-of-sight movement on the Earth’s surface. The relative movement generated between consecutive images affects the image registration accuracy of cloud animation. In this study, the imager on the Chinese FY-4 satellite that was launched in December 2016 is used as the research object. Moreover, a strict definition of image reference is given, and an orbital motion compensation method (OMC) is studied. By adding scan compensation to the imager 2-D scanning mechanism, the scanning path of the line of sight is navigated on the satellite in real time. Satellites are equivalent to viewing at ideal orbital positions. As a result, satellite remote sensing images are accurately registered to the Earth-fixed grid, and a relatively fixed geometric relationship is maintained. The correlation between L0 data and the measurement information of satellite orbit is removed due to the compensation performed on the satellite. Therefore, the long-term registration stability of the original image is guaranteed from the root. L0 remote sensing data from the FY-4 on-orbit test are used for experimental verification to prove the accuracy of the method. The results show that the relative movement of the north–south directions of the cloud animation is reduced from 973.0 μrad to 75.6 μrad (3σ) and that of the east–west direction is reduced from 205.8 μrad to 81.2 μrad (3σ). The interference of the orbital motion on the image navigation and registration is effectively reduced by the OMC on the satellite. In view of the development trend of the future imager of the geostationary meteorological satellite, the problem of the edge pixel error of the long aperture array detector caused by satellite orbital motion compensation is analyzed. Furthermore, a solution to reduce the edge error by maintaining the satellite near 0° inclination using an electric propulsion system is proposed.关键词：geostationary meteorological satellite;Fengyun-4;FY-4;image registration;INR;orbital motion compensation;OMC- 589
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发布时间：2021-06-07 - 摘要：Micro-nano satellite is one of the developing trends of remote sensing technology with the advantages of light-weight, small size, low cost. However, because of the limitation of the volume and weight, the traditional high resolution optical imaging payload with long focal length and large aperture is difficult to apply to earth observation of micro-nano satellite. In order to solve this problem, a super-resolution imaging scheme is demonstrated in this paper. First, in the mode of images acquisition, to obtain multi frame images of the same region, the velocity of imaging relative to the ground should be controlled by satellite attitude. And because the attitude control deviation of satellite is objective, so subpixel displacement information can be generated by pitching, yaw, and rolling random deviations, without to install any other displacement generators; Secondly, In the super-resolution reconstruction algorithm, aiming at solving the problem of prior constraints on variational bayesian super-resolution reconstruction method, we propose a weighted bi-directional difference prior model to overcome the under-constraint of non-edge regions of image due to total variation prior and L1 norm prior, to further restrain the solving space of the observation equation. The above scheme is applied to the China’s first super-resolution imaging micro-nano satellite:CX-6(02) micro-nano satellite. The imaging results of this satellite show that: our images acquisition method can obtain sufficient subpixel information, which is approximately uniformly distributed with 0.1 pixel magnitude; The result of super-resolution reconstruction is superior to the same variational bayesian method based on L1 norm prior model and total variation prior model, it is hardly to introduce or amplify the computational noise in the iterative process of the algorithm, effectively weakens the ill-posed property of the deconvolution operation. Make the CX-6(02) satellite’s imaging resolution increased from 2.8 to 1.4 meters in the 700 km orbit altitude, and the whole satellite is only 66 kg. Except for micro-nano satellite, the design scheme of this paper can also be applied to medium or large optical imaging satellite, it may provide a certain theoretical and experimental support for high resolution earth-observing remote sensing.关键词：CX-6(02) micro-nano satellite;super-resolution imaging;images acquisition;reconstruction algorithm;variational Bayes;prior model
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发布时间：2021-06-07 - 摘要：The spatial and radiation resolutions of domestic satellites have been remarkably improved in recent years. The sensor design and geometric calibration technologies have improved with the development and application of stereo mapping satellites (ZY-3). However, the imaging systems typically use the linear CCD imaging technology. The long focal length and narrow field angle causes the geometrical model to have 3D parallel projection characteristics, and the satellite images will still have residual system errors caused by the drift error of satellite-borne GPS/IMU and asynchrony between the pose and trace of the satellite, especially after the rigorous on-orbit geometry calibration. A block adjustment technique is still required to meet the requirements of remote sensing monitoring and mapping application. Therefore, satellite images-based accurate positioning without ground control point information is the precondition to obtain the global geographic and resource environmental information and monitoring changes in the global resource environment. The accuracy of “ZY-3” satellite image is improved to 15 m after calibration and its internal precision is better than 1 pixel. After the overall block adjustment without GCPs, the plane and elevation accuracy of the image can be improved to 5 m (medium error). In this study, on the basis of the widely used optimization method of solving the constraint problem in photogrammetry–alternating direction method (ADM) and RFM least-squares block adjustment, we propose a GCP-independent block adjustment method for large-scale domestic high-resolution optical satellite images–GCP-independent satellite imagery block adjustment (GISIBA) based on the geometric features of ZY-3 satellite images. The proposed method is highly efficient and easy to parallelize. GISIBA of satellite images can be considered as the overall block adjustment of the multi-source optical satellite imagery with specific constraints (distance, angle, etc.) when no ground control points are available. Most GCP-independent adjustments use a form of virtual control points. However, the precision of these virtual control points is low (varied system error), and the precision is inconsistent in the measurement area. Thus, the GCP-independent adjustment is a type of block adjustment under different precision controls. The law of error propagation of this approach is complex, and gross error detection and positioning are difficult to perform using this approach. This study presents an “average” virtual control point-based stereoscopic GCP-independent block adjustment method for large-scale satellite image GISIBA. On the basis of the automatic and reliable acquisition of uniformly distributed image tie points, the method comprehensively uses the “ADM” introduced from aerial photogrammetry and RFM-based least squares adjustment algorithm to realize the combined block adjustment of satellite images. First, the “ADM” is used to solve the initial values of the unknowns and to perform automatic detection and elimination of the above medium-scale gross error based on the parallel processing platform. All unknowns are assigned priori weights based on the results. Next, the RFM-based least square method is used to solve the large-scale reformation normal equation to obtain the orientation parameters with high-precision, which meets the production requirement of high-precision image products. Block adjustment by constructing virtual “average” control points addresses the “rank” problems in the GCP-independent adjustment and improves the state of normal equation of the block adjustment system, which benefits the stability and fast convergence of the block. Moreover, the method makes it convenient to analyze the relationship among the data coverage, imaging time interval, and satellite image GCP-independent block adjustment. In addition, parallel processing based on the OMP parallel method is used to realize the parallel processing of the “ADM” and multi-thread parallel computing based on least-squares adjustment to ensure the efficiency of block adjustment. We used multiple sets of the ZY-3 satellite image data in typical regions to verify our method. The following experiment results are summarized as follows: 1) On the basis of the widely used optimization method of constraint problem called the “ADM” and RFM least-squares block adjustment, the proposed GISIBA method is easy to parallelize and is highly efficient in terms of reliability, accuracy, and performance of the developed procedure. 2) In this method, virtual “average” control points are built to solve the rank defect problem and qualitative and quantitative analyses in block adjustment without control. Assuming the positioning accuracy is located on the same number order (such as 50 m), the final positioning accuracy of satellite image must be improved after GCP-independent block adjustment by using the virtual “average” control points. The final positional accuracy is stronger than the worst initial positioning accuracy of the original image. Furthermore, the increase on the coverage of satellite images does not consistently improve the overall positioning accuracy. However, the use of considerable high-resolution satellite images to cover the same area improves the positioning accuracy after the final block adjustment in the statistical sense. The horizontal and vertical accuracies of multi-covered and multi-temporal satellite images are greater than 6 m and 5 m, respectively. 3) The mosaic problem of adjacent areas in large area DOM production can be solved when third-party geographic information data are introduced as horizontal and vertical constraints. This approach is considered as weak-sense auxiliary control in the block adjustment process.关键词：GCP-independent orientation;Rational Function Model (RFM);virtual control points;block adjustment;alternating direction method;ZY-3 satellite image
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发布时间：2021-06-07 -
摘要：Sunlight incoming sea surface forms ocean glint (OG) in a special area and shows strong reflection and polarization characteristics. OG significantly influences the imaging quality of ocean remote sensing, especially because the interference is large for clouds and aerosols above the ocean surface. Therefore, eliminating OG is the key problem to be solved in the process of remote sensing data. At present, most OG detections of sensors are utilized by a rough sea surface polarization model combined with an empirical threshold. Orbit height and resolution is different from various sensors available. Thus, the result is quite inaccurate using the same threshold to discriminate glint pixels, thereby resulting in several pixels being utilized ineffectively. The Chinese GF-5 satellite has been scheduled for launch in 2017. It carries a Directional Polarimetric Camera (DPC) sensor for the atmospheric polarization research at a global scale. Similarly, the OG detection is essential to DPC data processing. The traditional method cannot achieve the dynamic detection of OG for different satellite data. Thus, the problem of accurately obtaining a threshold angle has become the key difficulty of OG dynamic detecting research. OG dynamic detecting (OGDD) method was proposed on the basis of near-infrared (NIR) polarized data, which were not easily affected by atmospheric disturbance under a clear sky. From these data, several parameters, such as the geometry conditions of solar and observation and sea surface wind speed and direction, could be obtained. According to ocean–atmosphere coupled radiative transfer theory, the OGDD model, combined with the OG and multi-directional NIR-polarized radiation information (865 nm), was developed on the basis of the regular performance of the NIR-polarized radiation characteristic. The OGDD was realized by obtaining the dynamic threshold of a glint angle. A calibration layer was selected by using the polarized characteristic tendency of an OG center from detecting layers, and after cloudy pixels have been removed, a slope dynamic analysis was conducted on the basis of an OG-polarized radiative regular variety on top of the atmosphere. Finally, the ocean pixels were marked as glint pixels using the dynamic threshold of the glint angle. This study used PARASOL/POLDER3 satellite data as the research object for the DPC simulation and selected the Indian Ocean as the study area. The NIR channel utilized the OGDD model to acquire apparent and polarization reflectivity (865 nm) of the sea surface. The glint threshold was adjusted dynamically to 34° using the OGDD model. In comparison with MODIS 40°, the glint angle was reduced by approximately 15%, and the pixel-marked glint was relatively decreased by 30%. Similarly, in comparison with POLDER3 30°, the glint angle was relatively improved by nearly 13%, and the pixel-marked glint was increased by 30%. The model can effectively distinguish the glint and non-glint pixels through a dynamically adjusted threshold and significantly improve the utilization rate of the pixels by reducing the interference of aerosol retrieval at the clear sky area. Furthermore, this model can generate reliable data for cloud detection and microphysical characteristic retrieval and provide support to developing the in-flight calibration and aerosol inversion of the GF-5 satellite multi-angle polarization sensor.关键词：PARASOL;ocean-atmosphere coupled radiation;ocean glint;radiation information;polarized reflectance;Ocean Glint Dynamic Detecting;GF-5;polarization remote sensing- 600
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发布时间：2021-06-07 -
摘要：The situation of urban black and odorous water in China is serious, but the monitoring of this water is just starting from remote sensing and many problems need to be solved. The research provides technical support for the effective regulation of urban black and odorous river. Taking the main rivers in the urban built-up area of Shenyang city as the research object, we carried out ground surveys from 2015—2016 years, and obtained 46 general water samples in Hun river and Pu river, and 50 black and odorous water samples in Huishanming channel, Mantang river, Xi river, the river near the Weishanhu road, and the river of north of Dingxiang Lake, including the water spectrum and water quality parameters. Through the analysis of spectral characteristics of the black-odor water and general water , we found that the urban black and odorous water reflectance spectra in green - red band is gentler than the general water, then we put forward an index of BOI (Black and Odorous water Index) based on the reflectivity spectrum of black and odorous water recognition model. By comparing the BOI index with the ratio index of red and green bands (Wen, et al., 2018), BOI index has better recognition accuracy. The results show that: (1) When BOI based on the remote sensing reflectance (Rrs) is less than the threshold of 0.065, which can be awarded as black and odorous water. (2) Due to the difficulties of accurate atmospheric correction in GF2 image, Rayleigh scattering correction reflectance (Rrc) can be used to replace Rrs. When BOI is less than 0.05, it can be discriminated as black and odorous water. And the simulation prove that when the aerosol optical thickness increases gradually, the spectral differences of black and odorous water and general water will decrease, so this method is applicable to the clear image with small aerosol optical thickness (such as AOT (550) ≤0.5). (3) BOI based on Rrc can be applied to GF2 image better, and has better recognition accuracy. The results that are extracted from the three images from 2015 to 2016 are showed that the black and odorous phenomenon of Mantang river and Xinkai river have been gradually improved, but Huishanming channel is still serious. In this paper, the identification algorithm of black and odorous water is mainly based on the spectral characteristics of Shenyang city, it has been validated only in Shenyang, and further verification in other cities. And it is necessary to consider the influence of various factors on the reflectivity of water body in the future.关键词：GF-2;urban black-odor water bodies;Black-Odor water Index;BOI;remote sensing recognition- 860
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发布时间：2021-06-07 -
摘要：Synthetic aperture radar (SAR) has been adopted in this study to compensate for the shortage of obtaining structural information below the meadow covering. Structural information is obtained through field surveying and special remote sensing images. Influenced by weathering and meadow covering, the structural information in the meadow covering environment acquired through these methods is limited. Given its long wavelength, SAR has the advantage of penetrability, which can help in detecting structural information below the meadow covering. The technology can efficiently compensate for the disadvantage of spatial remote sensing and field observing in meadow covering area. This study aims (1) to establish a new method of structural interpretation in meadow covering based on GaoFen (GF)-3 Pol-SAR images; (2) to verify the application of GF-3 Pol-SAR images in four different atmosphere districts, namely, Gerze in Tibet, Nyingchi in Tibet, Qianjiadian in Beijing, and Sinan County in Guizhou Province; and (3) to interpret the faults and circular structures systematically in these areas and verify the authenticity and accuracy of interpretation through GF-3 SAR images by comparing with the 1∶50000 field mapping. GF-3 C-band SAR images have been used in detecting geology structures in this study because of its penetrability. GF-3 SAR images have the most observing modes worldwide. GF-3 full polarization mode images are utilized in this study to optimize the use of information in different polarization modes. To use the GF-3 SAR images effectively and accurately, the data processing procedure, including focusing, multi-looking, filtering, and geocoding, has been completed. The effect from speckle in the images can be effectively reduced by Lee filtering. Geocoding can ensure the accuracy of spatial information. The 90 m SRTM DEM data are obtained in the geocoding process to eliminate the topographic influence, which helps in optimizing the use of micro-topographic features to interpretation structures. On the contrary, the structures have different features in various polarization images. To optimize the use of features in different polarization images, the R-G-B combination of various polarization directions is used in the study. As the cross polarization has more peak features than the straight polarization, the cross polarization images have been merged as R channel and the straight polarization images have been merged as G and B channels. The interpretation capability of GF-3 SAR images has been increased by combining different polarization images. In this work, four study areas in different covering environments have been selected. The interpretation keys of faults and circular structures in study areas can be established on the basis of the combination of different polarization images, by analyzing the unique color, topography, and hydrographic features of faults and circular structures. The structural features have been systematically interpreted on the basis of the interpretation keys in four study areas. To analyze the authenticity and accuracy of interpretation through GF-3 SAR images, the structural features have been compared with the faults in 1∶50000 mapping. The color combination of different polarization images in four study areas has been acquired through data processing. Interpretation keys of faults and circular structures in study areas have been established by analyzing the unique color, topography, and hydrographic features of faults and circular structures. The structures in study areas have been interpreted systematically. Structural feature maps interpreted through GF-3 SAR images in study areas have been drawn. The faults in 1∶50000 field maps are contained in the structures interpreted through GF-3 SAR images, compared with 1∶50000 field mapping. The position of faults in 1∶50000 mapping fits the position of faults interpreted through GF-3 SAR images. The number of faults interpreted through GF-3 SAR images is largely increased. In this study, SAR has been adopted to detect geology structures. GF-3 SAR images have been used in four study areas, namely, Gerze in Tibet, Nyingchi in Tibet, Qianjiadian in Beijing, and Sinan County in Guizhou Province. By investigating structural interpretation through GF-3 SAR images in study areas, the following conclusions can be obtained: (1) A new method of structural interpretation in meadow covering based on GF-3 Pol-SAR images has been established. (2) The interpretation keys of faults and circular structures in four study areas, namely, Gerze in Tibet, Nyingchi in Tibet, Qianjiadian in Beijing, and Sinan County in Guizhou Province, based on GF-3 SAR images have been established. (3) The faults and circular structures in study areas have been interpreted systematically through GF-3 SAR images. The faults in 1∶50000 map have been contained in structural features interpreted through GF-3 SAR images, compared with 1∶50000 field mapping. The number of faults interpreted through GF-3 SAR images is largely increased. These increased faults are mostly structures below the meadow covering that cannot be observed through field work and special remote sensing images. The structural interpretation in four study areas demonstrates its authenticity and accuracy through GF-3 SAR images. The method based on GF-3 SAR images can effectively compensate for the disadvantage of field work and spatial remote sensing in meadow covering.关键词：GF-3;Pol-SAR;meadow covering;structure interpretation;Loop structure- 554
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发布时间：2021-06-07 -
摘要：High-level geological disasters are characterized by strong concealment, strong destructiveness, and difficulty in investigation. These disasters have frequently occurred in the mountainous areas of Southwest China in recent years, thereby causing serious casualties and property losses to mountain residents. Remote sensing technology has the advantages of short response time, intuitive image, high resolution, and extensive monitoring range. An image is highly achievable, easy to obtain, low cost and reliable, and can be “acquired.” On the basis of the Gaofen-2 and TRIPLESAT (Beijing-2) images as the data source, this study conducted an emergency monitoring of the “10·11” Jinsha River high-level landslide and analyzed the landslide disaster situation, disaster evolution, and pre-disaster creep characteristics. The second investigation was performed after the disaster in the vicinity of a barrier lake. A total of 2 suspected cracks in the entire area of the barrier lake, 16 hidden dangers in the landslide, and 5 inundation areas were found. Results showed that domestic remote sensing satellites demonstrate considerable application prospects for the emergency monitoring of severe geological disasters.关键词：remote sensing technology;high ground disaster;Jinsha River landslide;disaster monitoring;Baige Lake- 657
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发布时间：2021-06-07
Chinese Satellites
Fundamental Research
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摘要：Remote sensing images have been a crucial data source for land cover mapping and other applications. However, optical remote sensing images are frequently contaminated with clouds. Clouds have caused several limitations in remote sensing applications through optical satellite. Although several approaches have been conducted for cloud detection, they still fail to distinguish bright surfaces, snow, and clouds, especially for seasonally snow-covered images. Therefore, we aim to develop a fast and universal cloud detection method, which can accurately detect clouds in complex areas. Considering that many sensors do not have a thermal infrared band, we only use the visible, near infrared, and short-wave infrared bands to detect clouds. The proposed method is expected to be used for a variety of satellite data. In this study, a multi-temporal cloud detection method was proposed for optical images. Given that snow and clouds have a big difference in short-wave infrared bands, we first developed an Enhanced Cloud Index (ECI) based on the spectral properties of the bands to distinguish them. Then, we proposed an Enhanced Multi-Temporal Cloud Detection (EMTCD) algorithm based on the ECI index and multi-temporal images to extract cloudy pixels. Finally, we tested and compared the algorithm with three classical cloud detection algorithms, namely, Function of mask (Fmask), Cloud Cover Assessment (CCA), and Multi-Temporal Cloud Detection (MTCD) algorithms, to verify the accuracy of the proposed algorithm. Landsat-8 images were used as the data source in this study. Given that many operational cloud detection methods had failed in complex areas, we selected four Landsat-8 OLI scenes in two test areas with typical seasonal snow cover and complicated land covers as our test data. The images were all obtained from 2015. The test areas were the northeast and southwest of China. Test results indicated that the ECI index can effectively distinguish snow and clouds. The ECI index of snow was higher than that of clouds. The EMTCD method performed well in cloud detection, which had the best cloud detection result with an overall accuracy of 93.2% compared with that of 81.85%, 66.14%, and 86.3% for the classic Fmask, MTCD, and CCA cloud detection methods, respectively. The ECI index is effective in distinguishing clouds and snow. The EMTCD algorithm can provide a good performance in cloud detection without using the thermal infrared band, even for seasonally snow-covered regions with complicated high brightness ground surface, which is always challenging for traditional cloud detection algorithms. However, the method is developed based on multiple images. Compared with single temporal methods, the proposed method still has some limitations.关键词：cloud detection;Enhanced Cloud Index;multi-temporal;Landsat-8;multi-spectral- 631
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发布时间：2021-06-07 - “资源三号02星搭载激光测高载荷，提出激光数据辅助卫星立体影像成像几何模型精化处理理论。湖北、青海试验表明，该方法可有效提高卫星立体数据测图精度。”摘要：ZiYuan3-02 (ZY3-02), which was launched on May 30, 2016, is the second satellite in the ZiYuan3 series and is mainly used for developing China’s civil space infrastructure. A laser altimeter, a core payload in ZY3-02, is China’s first earth observation laser altimeter experimental instrument. Evaluation accuracy is a crucial factor in stereoscopic mapping and is occasionally even more difficult to improve than a planar. In the conventional block adjustment combined with the increasing accuracy of laser altimeter data and the characteristics of laser altimetry data in the ZY3-02 satellite, in this study, we proposed a geometric imaging model refinement general theory of satellite stereo images aided with the laser altimeter data. First, high-precision tie point matching in the conventional block and free network adjustments without constraints were conducted to obtain a high-precision relative accuracy and absolute precision, which was not worse than that in the original imaging geometric model; second, in accordance with the 3D coordinates of the laser altimetry data and refined imaging geometric model of reference data, the reference image point coordinates could be acquired. These coordinates were used to map the target image point coordinates using the geometric model, and high-precision homonymous image points could be determined in the target images after a refinement process through the tie point matching algorithm; finally, the block adjustment with the homonymous points as elevation controls was performed to further process the imaging geometry model and compute high-precision compensation parameters. The experiments in Hubei and Qinghai showed that the elevation accuracy of the satellite geometry model refined by altimeter data can reach 1.97 and 3.23 m, correspondingly. The comparison experiments in Hubei and Xinjiang area presented with an obvious phenomenon wherein the system error became large given the weakening of the control strength. The abovementioned experiments demonstrate that the proposed method could effectively improve the accuracy of satellite stereo mapping. The application of the laser altimetry data was subject to the topographic relief. The laser altimetry data would become increasingly effective in a flat area but require a certain pre-process in mountainous areas before use. In practical applications, the laser data should be distributed evenly at no more than one track in the space interval.关键词：ZY3-02 satellite;laser altimetry;geometry model refined;stereo images
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发布时间：2024-10-10 - 摘要：Oil spill is one of the most common causes of marine pollution. Synthetic aperture radar (SAR) can detect marine oil spills due to its all-weather and all-day imaging capability. However, conventional algorithms using single-channel SAR usually confuses oil spills with oil spill lookalikes, making oil spill detection a challenging task. In recent years, polarimetric SAR has been studied to improve oil spill detection performance, particularly with respect to distinguishing oil spills and lookalikes. Compact polarimetric (CP) SAR is one of the most popular trends of polarimetric SAR platforms. Compared with full polarimetric SAR, CP SAR contains abundant polarization information of scattering targets. CP SAR also has large imaging range and its manufacturing cost is considerably low. Therefore, CP SAR is a promising tool for oil spill detection. In this study, we utilized CP HP-mode data and derived three parameters to distinguish oil spills from lookalikes. The three novel parameters are CP entropy (Hc), CP fraction (PFc), and CP pedestal height (PHc), which are conducted from CP eigenvalue decomposition. The scattering type of sea surface is dominated by low entropy scattering. For instance, Bragg scattering from small rough surfaces can be regarded as weakly depolarized. In this vein, CP eigenvalue
$\hat I {\gg 1}$ $\hat I {\gg 2}$ 关键词：oil spill detection;compact polarimetric SAR;eigenvalue decomposition;compact polarimetric parameter;Bragg scattering- 593
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发布时间：2021-06-07
Technology and Methodology
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摘要：Estuary wetland is a special wetland type, and the extraction of estuary wetland information plays an important role in wetland conservation and scientific research. In this study, Yellow River Delta wetlands, as a typical estuary wetland in the north part of China, are considered the study area. The random forest method, which has evident advantages in feature selection and classification, was chosen to extract wetland information from the study area. First, five different characteristic variables, namely, spectral features, vegetation index, water index, red edge index, and texture features, were generated based on Sentinel-2 data with rich multi-temporal and spectral information. Then, six different classification schemes were constructed based on the preceding characteristic information. Finally, random forest classifier was used to extract the wetland information of the Yellow River Delta and verify the extraction accuracy of different results. The purpose is to select the best plan to improve the effect of wetland information extraction. Results are as follows: (1) The effective use of multiple feature variables is the key to improving the extraction of wetland information. The contribution of different characteristics to the wetland information extraction is described as follows: the red edge index > vegetation index and water index > spectral feature > texture feature. (2) The preferred features based on the random forest algorithm are crucial to extraction accuracy, with an overall accuracy of up to 90.93%, and Kappa coefficient of 0.90. This result shows that the random forest algorithm can effectively process feature selection. In feature variable data mining, the accuracy of the wetland information extraction can be guaranteed, and the operation efficiency can be improved. This study also provides a new idea, method, and technology for the selection of data sources and feature and method selections for wetland information extraction.关键词：estuarine wetland;information extraction;Sentinel-2;Random Forest;feature selection;red edge index;multi-temporal data- 992
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发布时间：2021-06-07 -
摘要：Spatial information technology is a strategic and emerging industry worldwide. The diversified application of remote sensing technology and massive data featuring the integration of spatial information technology with the big data era has now become a mere reality. Hainan Province, relying on its unique natural and geographical environment, adheres to ecological development and is the largest provincial-level special economic zone in China. Hainan Province is also currently implementing a national strategy for an international tourism island. The major scientific and technological plan for Hainan Province, which was established in 2016, is a demonstration project for the construction and application of the remote sensing big data service platform in the province. With the large-data infrastructure and intelligent shared service platform represented by the Hainan remote sensing big data cloud, the demonstration of space technology applications in a typical industry in Hainan Province is realized to meet the needs of spatial information products in the socio-economic development in the new era of personalized shared service requirements. The project focuses on numerous key technical problems in the sharing of large-scale space observation data and information products, eliminating the current spatial data dispersion and information of island phenomenon, improving the accuracy and timeliness of spatial information acquisition, and achieving information resource sharing and efficient service. Under the integrated remote sensing big data service platform, application demonstration is conducted in typical industries, such as coastal zone, agriculture, forestry, tourism, urban environment, and provincial-level application-oriented information system for typical industries. The big data service platform envisages to provide timely and effective dynamic monitoring information to scientific decision-making platform to further enhance the ability of the government departments in resource and environmental management and achieve coordinated and sustainable development of resources, environment, economy, and society of the province.关键词：Hainan province;remote sensing big data;resources and environment;application demonstration- 734
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发布时间：2021-06-07 -
摘要：Ocean remote sensing is the only effective method for monitoring the marine ecosystem on a global scale in the long term. This method has played a crucial role in the research of carbon cycle, global changing, and ocean acidification and its biological impacts. The validation of ocean color products is quite important for the improvement of the algorithm and the reliability of further application. Given the complex and highly dynamic optical marine characteristics, especially for case Ⅱ water, the evaluation of accuracy and the expression of remote sensing products have become difficult, and considerable research has focused in this field. This study aims to create a scientific evaluation method of the representativeness of ground stations and the heterogeneity of remote sensing pixels of sea surface temperature (SST) verification. The temporal and spatial variation parameters, including the statistical standard deviation of time series, the spatial variation index, and the frontal index, are designed. The analytic hierarchy process for determining the weight of different indices and the method for regionalizing the interval of a spatiotemporal variation. Verification datasets are classified using a distribution map of the spatiotemporal variation of space level division. Result of the experimental data shows that spatiotemporal variation is a direct cause of errors. Considering the strong spatiotemporal variation, numerous verification errors are introduced in the verification process, which uses data from different variation grade divisions, and the relative error of the verification result can reach more than 13.08%. The spatial distribution of spatiotemporal variation is large in the Yellow and Bohai Sea regions and small in the East and South China Seas. The seasonal variation is strong in winter and spring and weak in summer and autumn. In this study, we propose models and methods to reasonably select representative validation datasets and verify the scientific nature of the method from the experimental data. In the region where the spatiotemporal variability is intense, the verification errors are large. These errors are not completely remote sensing product errors. The results of verification are not representative and cannot really reflect the error characteristics of remote sensing products. For SST ocean remote sensing product verification, spatiotemporal variability and its contribution to the validation error must be considered. Moreover, a reasonable selection of evaluation data set, scientific method, and representative test area must be verified.关键词：ocean remote sensing;sea surface temperature;spatial-temporal variance;accuracy and uncertainty;level division;validation- 586
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发布时间：2021-06-07 -
摘要：In this study, a monthly probability distribution of different cloud phases, effective radii, and top temperatures in Huaibei region based on MODIS cloud product data (MYD06) from 2006 to 2015 were analyzed contrastively. Moreover, annual variations of cloud water path were discussed. Results showed that a water cloud probability of occurrence during summer, autumn, and winter in Huaibei region is high, whereas an ice cloud probability of occurrence during spring and summer is high. The annual average of water cloud probability is nearly 2 times that of ice cloud, that of clear sky is the same as ice cloud, and that of the mixed cloud is relatively minimal. The monthly probability distribution of water cloud effective radius has varied annually, except in July. Water cloud is mainly distributed between 5 and 30 μm. Ice cloud effective radius is mainly distributed between 15 and 35 μm. The monthly probability distribution of ice cloud particle effective radius has changed monthly in ten years, except in August and May. A mixed cloud effective radius is mainly distributed between 10 and 40 μm, and the monthly probability appears two peaks between 10 and 20 μm and between 25 and 35 μm. It is different from water and ice clouds, and it is obvious during spring, autumn, and winter. During the studied decade, the annual average of cloud water path in Huaibei region is below 300 g/m2. During winter, the annual average of cloud water path is relatively decreasing annually. The monthly probability distribution change of the cloud top temperature in summer has been smaller than the other seasons in ten years. The cold cloud occurrence probability during spring and winter is significantly high, and the warm cloud probability of occurrence during summer and autumn is higher than that of the cold cloud.关键词：cloud properties;cloud phase;cloud effective radius;cloud top temperature;cloud water path;Huaibei region;weather modification- 663
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发布时间：2021-06-07
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