scholarly journals ON-ORBIT GEOMETRIC CALIBRATION APPROACH FOR HIGH-RESOLUTION GEOSTATIONARY OPTICAL SATELLITE GaoFen-4

2016 ◽  
Vol XLI-B1 ◽  
pp. 389-394 ◽  
Author(s):  
Mi Wang ◽  
Yufeng Cheng ◽  
Xiaoxiang Long ◽  
Bo Yang
Keyword(s):  
Measurement Error ◽  
High Resolution ◽  
Parameters Estimation ◽  
Imaging Features ◽  
Geometric Calibration ◽  
Area Array ◽  
Imaging Model ◽  
Internal Parameters ◽  
Array Camera ◽  
Calibration Parameters

The GaoFen-4 (GF-4) remote sensing satellite is China’s first civilian high-resolution geostationary optical satellite, which has been launched at the end of December 2015. To guarantee the geometric quality of imagery, this paper presents an on-orbit geometric calibration method for the area-array camera of GF-4. Firstly, we introduce the imaging features of area-array camera of GF-4 and construct a rigorous imaging model based on the analysis of the major error sources from three aspects: attitude measurement error, orbit measurement error and camera distortion. Secondly, we construct an on-orbit geometric calibration model by selecting and optimizing parameters of the rigorous geometric imaging model. On this basis, the calibration parameters are divided into two groups: external and internal calibration parameters. The external parameters are installation angles between the area-array camera and the star tracker, and we propose a two-dimensional direction angle model as internal parameters to describe the distortion of the areaarray camera. Thirdly, we propose a stepwise parameters estimation method that external parameters are estimated firstly, then internal parameters are estimated based on the generalized camera frame determined by external parameters. Experiments based on the real data of GF-4 shows that after on-orbit geometric calibration, the geometric accuracy of the images without ground control points is significantly improved.

scholarly journals ON-ORBIT GEOMETRIC CALIBRATION APPROACH FOR HIGH-RESOLUTION GEOSTATIONARY OPTICAL SATELLITE GaoFen-4

2016 ◽  
Vol XLI-B1 ◽  
pp. 389-394
Author(s):  
Mi Wang ◽  
Yufeng Cheng ◽  
Xiaoxiang Long ◽  
Bo Yang
Keyword(s):  
Measurement Error ◽  
High Resolution ◽  
Parameters Estimation ◽  
Imaging Features ◽  
Geometric Calibration ◽  
Area Array ◽  
Imaging Model ◽  
Internal Parameters ◽  
Array Camera ◽  
Calibration Parameters

The GaoFen-4 (GF-4) remote sensing satellite is China’s first civilian high-resolution geostationary optical satellite, which has been launched at the end of December 2015. To guarantee the geometric quality of imagery, this paper presents an on-orbit geometric calibration method for the area-array camera of GF-4. Firstly, we introduce the imaging features of area-array camera of GF-4 and construct a rigorous imaging model based on the analysis of the major error sources from three aspects: attitude measurement error, orbit measurement error and camera distortion. Secondly, we construct an on-orbit geometric calibration model by selecting and optimizing parameters of the rigorous geometric imaging model. On this basis, the calibration parameters are divided into two groups: external and internal calibration parameters. The external parameters are installation angles between the area-array camera and the star tracker, and we propose a two-dimensional direction angle model as internal parameters to describe the distortion of the areaarray camera. Thirdly, we propose a stepwise parameters estimation method that external parameters are estimated firstly, then internal parameters are estimated based on the generalized camera frame determined by external parameters. Experiments based on the real data of GF-4 shows that after on-orbit geometric calibration, the geometric accuracy of the images without ground control points is significantly improved.

Abstract WMP71: Moyamoya-atherosclerosis Syndrome: Clinical and High-resolution Magnetic Resonance Imaging Features

Stroke ◽  
2017 ◽  
Vol 48 (suppl_1) ◽  
Author(s):  
Lian Duan ◽  
Wei-Hai Xu ◽  
Cong Han
Keyword(s):  
Magnetic Resonance Imaging ◽  
Risk Factors ◽  
Magnetic Resonance ◽  
High Resolution ◽  
Moyamoya Disease ◽  
Treatment Strategies ◽  
Diagnostic Process ◽  
Imaging Features ◽  
Intracranial Atherosclerosis ◽  
Resonance Imaging

Introduction: The diagnosis in the patients with angiographic moyamoya findings and atherogenic risk factors is challenging. In this study, we try to incorporate high-resolution magnetic resonance imaging (HRMRI) into the diagnostic process of intracranial atherosclerosis associated moyamoya syndrome. Methods: From March 2013 to March 2014, HRMRI was consecutively performed on adult patients with angiographic moyamoya. The patients were classified as moyamoya - plaques (MMD-P) if a plaque could be identified or as moyamoya - no plaques (MMD-NP) if a plaque could not be identified. The angiography, HRMRI findings and atherogenic risk factors of these patients were analyzed. Results: Fifty-one patients (mean age 39±9, 20 males) were enrolled. On traditional angiography, probable intracranial atherosclerosis was identified in 5 patients, no definite diagnosis in 12 patients, and moyamoya disease in 34 patients. On HRMRI, 15 out of 32 patients with risk factors and 4 out of 19 patients without risk factors were found to have plaques and were diagnosed as MMD-P, while the other 32 patients were diagnosed as MMD-NP. The MMD-P patients were more likely to be older and male and were less likely to have cerebral hemorrhage and a history of disease progression. Conclusions: Our study suggests that HRMRI can help diagnose intracranial atherosclerosis more accurately in moyamoya disease patients with atherogenic risk factors. The distinct clinical features between MMD-P and MMD-NP patients suggest different underlying pathophysiology and therefore potentially different treatment strategies.

scholarly journals Design for a Highly Stable Laser Source Based on the Error Model of High-Speed High-Resolution Heterodyne Interferometers

Sensors ◽  
2020 ◽  
Vol 20 (4) ◽  
pp. 1083
Author(s):  
Hongxing Yang ◽  
Ziqi Yin ◽  
Ruitao Yang ◽  
Pengcheng Hu ◽  
Jing Li ◽  
...  
Keyword(s):  
Measurement Error ◽  
High Resolution ◽  
High Speed ◽  
Beat Frequency ◽  
Error Model ◽  
Laser Source ◽  
Measurement Error Model ◽  
High Resolution Measurement ◽  
Resolution Measurement ◽  
The Impact

Heterodyne interferometers with two opposite Doppler shift interference signals have been proposed for high-resolution measurement with high measurement speed, which can be used in the background of high-speed high-resolution measurement. However, a measurement error model for high-speed high-resolution heterodyne interferometers (HSHR-HIs) has not yet been proposed. We established a HSHR-HI measurement error model, analyzed the influence of beat frequency stability with a simplified optical structure, and then designed an offset-locked dual-frequency laser source with a digital control system to reduce the impact of beat frequency drift. Experiments were used to verify the correction of the measurement error model and the validity of the laser source. The results show that the new laser source has a maximum beat frequency range of 45 MHz, which shows the improvements in the measuring speed and resolution.

Design and Calibration of a 3D High-Resolution Surface Profiling System Using Photometric Stereo

2015 ◽  
Author(s):  
Boren Li ◽  
Tomonari Furukawa
Keyword(s):  
High Resolution ◽  
Light Intensity ◽  
Target Surface ◽  
Photometric Stereo ◽  
Radiometric Calibration ◽  
Geometric Calibration ◽  
Surface Profiling ◽  
Surface Normal ◽  
3D Methods ◽  
Intensity Calibration

This paper presents the design and calibration of a 3D high-resolution surface profiling system using photometric stereo (PS). This system is mainly composed of a high resolution DSLR camera with a macro lens facing perpendicularly to the target surface, and several LEDs tilting towards the surface constrained by a light fixture. With each LED turned on at a time to create one lighting direction, the camera fixed at the same position captures an image. PS with surface normal integration (SNI) are then performed to reconstruct the surface in 3D. Methods of four calibrations for the developed system are proposed to achieve better accuracy, which are the camera radiometric calibration, the camera geometric calibration, the light direction calibration and the light intensity calibration. Experiments have demonstrated that the developed system with the calibration processes could achieve the accuracy in the order of 10 microns.

Principles Of A High Resolution Forest Imaging Model For Sar

2005 ◽  
Author(s):  
R.J. Miller ◽  
L.M.J. Brown ◽  
A.J. Siebert
Keyword(s):  
High Resolution ◽  
Imaging Model

scholarly journals Improvement and Assessment of the Absolute Positioning Accuracy of Chinese High-Resolution SAR Satellites

2019 ◽  
Vol 11 (12) ◽  
pp. 1465
Author(s):  
Deng ◽  
Zhang ◽  
Cai ◽  
Xu ◽  
Zhao ◽  
...  
Keyword(s):  
High Resolution ◽  
Propagation Delay ◽  
Reference Points ◽  
Calibration Model ◽  
Land Resource ◽  
Positioning Accuracy ◽  
Geometric Calibration ◽  
Atmospheric Propagation ◽  
Absolute Positioning ◽  
The Absolute

In recent years, China has launched YaoGan-13 and GaoFen-3, high-resolution synthetic aperture radar (SAR) satellites that can acquire global high-resolution images. The absolute positioning accuracy of such satellites is important for mapping areas without ground reference points and for automated processing. However, satellites without geometric calibration have poor absolute positioning accuracy, greatly restricting their application (e.g., land resource surveys). Therefore, they cannot meet national demands for high-resolution SAR images with good geometric accuracy. Here, we propose a series of methods to improve the absolute positioning accuracy of YaoGan-13 and GaoFen-3, such as the multiple-image combined calibration strategy and geometric calibration model for a real continuously moving configuration, including consideration of atmospheric propagation delay. Using high-accuracy ground control data collected from different areas, the 2-D and 3-D absolute positioning accuracies of YaoGan-13 and GaoFen-3 were assessed after implementation of the improvement measures. Experimental results showed that, after calibration, the 2-D absolute positioning accuracy of YaoGan-13 and GaoFen-3 are improved from 43.86 m to 2.57 m and from 30.34 m to 4.29 m, respectively. In addition, the 3-D absolute positioning accuracies of YaoGan-13 in plane and elevation are 3.21 m and 2.22 m, respectively. Improving the absolute positioning accuracy of these satellites could broaden the scope of their potential applications in the future.

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