- 标题
- 摘要
- 关键词
- 实验方案
- 产品
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A Comprehensive Evaluation of Approaches for Built-Up Area Extraction from Landsat OLI Images Using Massive Samples
摘要： Detailed information about built-up areas is valuable for mapping complex urban environments. Although a large number of classification algorithms for such areas have been developed, they are rarely tested from the perspective of feature engineering and feature learning. Therefore, we launched a unique investigation to provide a full test of the Operational Land Imager (OLI) imagery for 15-m resolution built-up area classification in 2015, in Beijing, China. Training a classifier requires many sample points, and we proposed a method based on the European Space Agency’s (ESA) 38-m global built-up area data of 2014, OpenStreetMap, and MOD13Q1-NDVI to achieve the rapid and automatic generation of a large number of sample points. Our aim was to examine the influence of a single pixel and image patch under traditional feature engineering and modern feature learning strategies. In feature engineering, we consider spectra, shape, and texture as the input features, and support vector machine (SVM), random forest (RF), and AdaBoost as the classification algorithms. In feature learning, the convolutional neural network (CNN) is used as the classification algorithm. In total, 26 built-up land cover maps were produced. The experimental results show the following: (1) The approaches based on feature learning are generally better than those based on feature engineering in terms of classification accuracy, and the performance of ensemble classifiers (e.g., RF) are comparable to that of CNN. Two-dimensional CNN and the 7-neighborhood RF have the highest classification accuracies at nearly 91%; (2) Overall, the classification effect and accuracy based on image patches are better than those based on single pixels. The features that can highlight the information of the target category (e.g., PanTex (texture-derived built-up presence index) and enhanced morphological building index (EMBI)) can help improve classification accuracy. The code and experimental results are available at https://github.com/zhangtao151820/CompareMethod.
关键词： classification,CNN,feature engineering,built-up area,Landsat 8-OLI,accuracy evaluation,feature learning
更新于2025-09-23 15:22:29
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Decimeter-Level Geolocation Accuracy Updated by a Parametric Tropospheric Model with GF-3
摘要： GaoFen-3 (GF-3) is a multi-polarization C-band synthetic aperture radar (SAR) satellite in China with a resolution of up to 1 m. Up to now, the geolocation accuracy of GF-3 could be improved to 3 m. According to the current study, there still exist meter-level geolocation residuals caused by atmospheric path delay after compensating with a static tropospheric model. In this paper, we compensate the residuals with the sophisticated tropospheric model based on real meteorological data. The experimental results show that the tropospheric model has an accuracy on the millimeter level, which can increase GF-3’s geolocation accuracy to several decimeters compared with the static tropospheric model.
关键词： GF-3,tropospheric model,geolocation accuracy,SAR
更新于2025-09-23 15:22:29
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Fiber Bragg Gratings Sensors for Aircraft Wing Shape Measurement: Recent Applications and Technical Analysis
摘要： The safety monitoring and tracking of aircraft is becoming more and more important. Under aerodynamic loading, the aircraft wing will produce large bending and torsional deformation, which seriously affects the safety of aircraft. The variation of load on the aircraft wing directly affects the ground observation performance of the aircraft baseline. To compensate for baseline deformations caused by wing deformations, it is necessary to accurately obtain the deformation of the wing shape. The traditional aircraft wing shape measurement methods cannot meet the requirements of small size, light weight, low cost, anti-electromagnetic interference, and adapting to complex environment at the same time, the fiber optic sensing technology for aircraft wing shape measurement has been gradually proved to be a real time and online dynamic measurement method with many excellent characteristics. The principle technical characteristics and bonding technology of fiber Bragg grating sensors (FBGs) are reviewed in this paper. The advantages and disadvantages of other measurement methods are compared and analyzed and the application status of FBG sensing technology for aircraft wing shape measurement is emphatically analyzed. Finally, comprehensive suggestions for improving the accuracy of aircraft wing shape measurement based on FBG sensing technology is put forward.
关键词： accuracy,aircraft,FBGs,wing shape measurement
更新于2025-09-23 15:22:29
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[IEEE 2018 China International SAR Symposium (CISS) - Shanghai (2018.10.10-2018.10.12)] 2018 China International SAR Symposium (CISS) - Compact Size Multi-Channel True Time Delay Moudle with High Accuracy
摘要： A 9-bit digital true time delay (TDD) and amplification module with high integration is proposed in this paper. The true time delay units, bi-directional amplifiers, serial-to-parallel converter and power pulse modulated circuits are integrated in a multi-chip module (MCM) with monolithic microwave integrated circuit (MMIC) and surface mount technology (SMT). Multi-layer microwave board is used to implement the routing of DC, control and RF signals. Moreover, in order to achieve better flatness of time delay, distributed amplifiers and high isolation cavity structures have been adopted. To calculate the spatial isolation of the cavity structures, electromagnetic simulation with microwave high frequency software has been utilized. For verification, a multi-channel TDD module has been designed, fabricated and measured. According to the measured results, the TDD module achieves the receive gain within 4.5 dB ± 0.8 dB, transmit power within 17dBm ± 1.0 dB, and high time-delay accuracy within ± 0.5 ps for 6.25 ps and ± 20 ps for 1600 ps, simultaneously.
关键词： high accuracy,compact size,multi-channel,true time delay
更新于2025-09-23 15:22:29
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A Multi-Segments Stitching Method for Profile Measurement of Large Scale Aspheric Surface within Submicrometer Accuracy
摘要： A multi-segments stitching method is proposed to obtain a two-dimensional profile of large scale aspheric components during the grinding process. We firstly analyze the corresponding relation between surface features of aspheric and measurement range of profilometer. According to multi-body system theory and slope difference, a mathematical model of multi-segments stitching method is constructed. Further, the multi-segments stitching errors based on 400 mm aspheric profile are simulated with different translation amounts, rotation angles, translation errors as well as rotation errors. The simulation results indicate that the translation error is the key factor for measuring the accuracy of the multi-segments stitching method. In addition, the standard deviations of multi-segments stitching errors are between 0.2 μm and 0.4 μm as the four factors are set to the proper values. To verify the simulation analysis results, an experimental setup, including Talysurf PGI 1240 and fixture, is applied to detect a 150 mm profile line on the aspheric surface. The experiment results show that the standard deviations of multi-segments stitching errors are almost within 1 μm when the rotation angle is under 7° and the translation amount is under 11 mm. The multi-segments stitching method can employ a small-range profilometer to achieve measurement of large-scale aspheric surfaces with submicrometer accuracy.
关键词： submicrometer accuracy,large-aperture aspheric surface,motion and motion errors,multi-segments stitching
更新于2025-09-23 15:22:29
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[IEEE 2018 IEEE International Conference on Imaging Systems and Techniques (IST) - Krakow (2018.10.16-2018.10.18)] 2018 IEEE International Conference on Imaging Systems and Techniques (IST) - Assessment of a Markerless Optical Tracking Technique for Computer-Assisted Hip Surgery
摘要： This article presents an evaluation of a prototype optical tracking system intended for use in computer-assisted orthopedic surgery. The device is based on a smartphone with a built-in video camera, and an external miniature time-of-flight camera. It is able to automatically recognize a surgical instrument based on its shape and appearance, and to determine its orientation relative to an array of light-reflective markers. The experiments were done in a measurement configuration and with the instruments that are specific to computer-assisted implantation of the acetabular component in total hip replacement surgery. The evaluation included the recognition rate of the instruments, and the angular accuracy of the system. The results show, that the accuracy is comparable to that obtained by conventional tracking devices in clinical settings, and partially meets the requirements specified in the literature for hip surgery.
关键词： optical tracking,surgical navigation,accuracy,computer assisted surgery,time of flight camera
更新于2025-09-23 15:22:29
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Performance study of surface plasmon resonance and lossy mode resonance based fiber optic sensors utilizing silver and indium oxide layers: An experimental investigation
摘要： This study presents here the experimental investigations on a surface plasmon resonance (SPR)/lossy mode resonance (LMR) based fiber optic sensors coated with silver and indium oxide layers. Different sensing probes have been fabricated by coating (i) a single layer of indium oxide, (ii) a single layer of silver and (iii) a double layer of indium oxide and silver (with different thicknesses) symmetrically onto to the bare core of silica fiber. The sensitivity of these fiber optic sensing probes towards surrounding region refractive index variations are determined using different concentrations of sucrose solutions. It was found that sensor probe fabricated with coating of 100 nm thickness of indium oxide was two times more sensitive than the conventionally used fiber optic sensing probe coated with only silver layer. The sensitivity of a double layer coated fiber optic sensor with various thicknesses of indium oxide and silver layers is in between the two extremes of the sensitivities. This study will find suitable applications in the field of chemical and biochemical sensing. The drawbacks of silver coatings and the advantages of LMR supporting indium oxide have also been discussed.
关键词： Surface plasmons,Sensitivity,Lossy mode resonances,Thin films,Fiber optic sensors,Detection accuracy,Indium oxide
更新于2025-09-23 15:21:21
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[IEEE IGARSS 2018 - 2018 IEEE International Geoscience and Remote Sensing Symposium - Valencia, Spain (2018.7.22-2018.7.27)] IGARSS 2018 - 2018 IEEE International Geoscience and Remote Sensing Symposium - The Wind Speed Inversion and In-Orbit Assessment of Imaging Altimeter on Tiangong-2 Space Station
摘要： Imaging ALTimeter (IALT) is a new type of radar altimeter system, which observes the earth from 2° to 7° incident angles. In comparison to the conventional altimeters such as HY-2A altimeter, Jason-1/2, TOPEX/Poseidon, which observe the ocean at nadir, the swath of IALT is much wider and its spatial resolution is much higher. The IALT on board Tiangong-2 space station is launched on 15th September, 2016 at Jiuquan Satellite Launch Center. The in-orbit assessment of IALT is done until 30th April, 2017. In this paper, the ocean surface wind speed inversion method based on IALT is established. The neural network algorithm is used for ocean surface wind speed retrieval, and the spatial resolution of retrieved wind speed is 25km. The wind speed inversion accuracy is evaluated by comparing with the ECMWF reanalysis wind speed, buoy wind speed, and boat measurement wind speed. The results show that the Root-Mean-Square (RMS) of retrieved wind speed is 1.85m/s, and the Bias of retrieved wind speed is about -0.21m/s. The wind speed inversion accuracy satisfies performance requirement.
关键词： in-orbit assessment,Imaging ALTimeter,ocean surface wind speed,inversion accuracy
更新于2025-09-23 15:21:21
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Determining the Optimum Number of Ground Control Points for Obtaining High Precision Results Based on UAS Images
摘要： Ground control points (GCPs) are used in the process of indirectly georeferencing Unmanned Aerial Systems (UAS) images. A minimum of three ground control points (GCPs) is required but increasing the number of GCPs will lead to higher accuracy of the final results. The aim of this study is to provide the answer to the question of how many ground control points are necessary in order to derive high precision results. To obtain the results, an area of about 1 ha was photographed with a low-cost UAS, namely, the DJI Phantom 3 Standard at two different heights, 28 m and 35 m above ground, the camera being oriented in a nadiral position, and 50 ground control points were measured using a total station. In the first and the second scenario, the UAS images were processed using the Pix4D Mapper Pro software and 3DF Zephyr, respectively, by performing a full bundle adjustment process with the number being gradually increased from three GCPs to 40. The third test was made with 3DF Zephyr Pro software using a free-network approach in the bundle adjustment. Also, the point clouds and the mesh surfaces derived automatically after using the minimum and the optimum number of GCPs, respectively, were compared with a terrestrial laser scanner (TLS) point cloud. The results expressed a clear overview of the number of GCPs needed for the indirect georeferencing process with minimum influence on the final results.
关键词： 3DF Zephyr Pro software,DJI Phantom 3 Standard,accuracy assessment,UAS images,ground control point
更新于2025-09-23 15:21:21
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Photothermal Effects Induced by Surface Plasmon Resonance at Graphene/Gold Nanointerfaces: A Multiscale Modeling Study
摘要： Surface plasmon resonance (SPR) biosensors have enormous potential in biological recognitions and biomolecular interactions, especially for the real time measurement of disease diagnosis and drug screening. Extensive efforts have been invested to ameliorate the sensing performances, while the photothermal effects, which are induced by the plasmon resonance, have an obvious impact. However, due to the limitations of experimental approaches, the theoretical mechanisms and specific influences of the SPR sensors with photothermal effects are few researched. Here, a multiscale simulation method is developed to investigate the photothermal effects at graphene/gold (Au) nanointerfaces, and to calculate the quantitative contribution of the photothermal effects towards high reliability SPR sensors in order to elucidate their influence on the sensing performances by means of first-principle calculations and molecular dynamics simulations. Our results indicate that the sensitivity and detection accuracy of graphene/Au SPR sensors can be tailored from 0 K to 600 K, due to the tunable dielectric constants of Au and graphene films through temperature variation. By controlling the its material thickness, interfacial combination and lattice strain, an optimized graphene/Au SPR sensor with higher sensitivity, detection accuracy, and reliability to the temperature rising has been achieved. Such multiscale simulation method, which is capable of seeking both the role and the underlying mechanism of the interfacial phenomena, can serve as an excellent guideline for the performance optimization and commercialized application of SPR sensors in the analytical chemistry and biomedical fields.
关键词： graphene/gold nanointerface,photothermal effects,surface plasmon resonance,multiscale simulation method,sensitivity and detection accuracy
更新于2025-09-23 15:21:21