scholarly journals GEOMETRIC CALIBRATION OF ZIYUAN-3 THREE-LINE CAMERAS COMBINING GROUND CONTROL POINTS AND LINES

Author(s):  
Jinshan Cao ◽  
Xiuxiao Yuan ◽  
Jianya Gong

Due to the large biases between the laboratory-calibrated values of the orientation parameters and their in-orbit true values, the initial direct georeferencing accuracy of the Ziyuan-3 (ZY-3) three-line camera (TLC) images can only reach the kilometre level. In this paper, a point-based geometric calibration model of the ZY-3 TLCs is firstly established by using the collinearity constraint, and then a line-based geometric calibration model is established by using the coplanarity constraint. With the help of both the point-based and the line-based models, a feasible in-orbit geometric calibration approach for the ZY-3 TLCs combining ground control points (GCPs) and ground control lines (GCLs) is presented. Experimental results show that like GCPs, GCLs can also provide effective ground control information for the geometric calibration of the ZY-3 TLCs. The calibration accuracy of the look angles of charge-coupled device (CCD) detectors achieved by using the presented approach reached up to about 1.0''. After the geometric calibration, the direct georeferencing accuracy of the ZY-3 TLC images without ground controls was significantly improved from the kilometre level to better than 11 m in planimetry and 9 m in height. A more satisfactory georeferencing accuracy of better than 3.5 m in planimetry and 3.0 m in height was achieved after the block adjustment with four GCPs.

Author(s):  
Jinshan Cao ◽  
Xiuxiao Yuan ◽  
Jianya Gong

Due to the large biases between the laboratory-calibrated values of the orientation parameters and their in-orbit true values, the initial direct georeferencing accuracy of the Ziyuan-3 (ZY-3) three-line camera (TLC) images can only reach the kilometre level. In this paper, a point-based geometric calibration model of the ZY-3 TLCs is firstly established by using the collinearity constraint, and then a line-based geometric calibration model is established by using the coplanarity constraint. With the help of both the point-based and the line-based models, a feasible in-orbit geometric calibration approach for the ZY-3 TLCs combining ground control points (GCPs) and ground control lines (GCLs) is presented. Experimental results show that like GCPs, GCLs can also provide effective ground control information for the geometric calibration of the ZY-3 TLCs. The calibration accuracy of the look angles of charge-coupled device (CCD) detectors achieved by using the presented approach reached up to about 1.0''. After the geometric calibration, the direct georeferencing accuracy of the ZY-3 TLC images without ground controls was significantly improved from the kilometre level to better than 11 m in planimetry and 9 m in height. A more satisfactory georeferencing accuracy of better than 3.5 m in planimetry and 3.0 m in height was achieved after the block adjustment with four GCPs.


Author(s):  
X. Tang ◽  
X. Zhu

Chinese ZY3-02 satellite, which is the second of ZY3 series satellites, was launched in May 30th 2016 for complementing the mapping and earth observation. In order to eliminate various system errors of the platform and payload, the on-orbit geometric validation and calibration was carried out. Firstly, we introduced the parameters of the three-line stereo camera and multispectral camera bound on ZY3-02 in this paper. There are four optical cameras on ZY3-02: a 4-band nadir-looking multi-spectral camera with 5.8 m resolution, a 2.1m resolution nadir-looking panchromatic band camera, as well as 2.5m resolution forward- and backward-looking panchromatic band cameras. Compared with ZY3-01, the resolution of the forward- and backward-looking cameras on ZY3-02 were upgraded from 3.5 m to 2.5 m. Then we presented the methods and datasets used for calibration in details. After our calibration, the total positioning accuracy of the three-line camera images is better than 10m without ground control points (GCPs). The plane and height accuracy are improved to 3 and 2 m respectively, with few control points. The band-to-band registration accuracy of the multispectral camera is better than 0.15 pixels.


Sensors ◽  
2021 ◽  
Vol 21 (19) ◽  
pp. 6668
Author(s):  
Linyi Jiang ◽  
Xiaoyan Li ◽  
Liyuan Li ◽  
Lin Yang ◽  
Lan Yang ◽  
...  

Affected by the vibrations and thermal shocks during launch and the orbit penetration process, the geometric positioning model of the remote sensing cameras measured on the ground will generate a displacement, affecting the geometric accuracy of imagery and requiring recalibration. Conventional methods adopt the ground control points (GCPs) or stars as references for on-orbit geometric calibration. However, inescapable cloud coverage and discontented extraction algorithms make it extremely difficult to collect sufficient high-precision GCPs for modifying the misalignment of the camera, especially for geostationary satellites. Additionally, the number of the observed stars is very likely to be inadequate for calibrating the relative installations of the camera. In terms of the problems above, we propose a novel on-orbit geometric calibration method using the relative motion of stars for geostationary cameras. First, a geometric calibration model is constructed based on the optical system structure. Then, we analyze the relative motion transformation of the observed stars. The stellar trajectory and the auxiliary ephemeris are used to obtain the corresponding object vector for correcting the associated calibration parameters iteratively. Experimental results evaluated on the data of a geostationary experiment satellite demonstrate that the positioning errors corrected by this proposed method can be within ±2.35 pixels. This approach is able to effectively calibrate the camera and improve the positioning accuracy, which avoids the influence of cloud cover and overcomes the great dependence on the number of the observed stars.


2005 ◽  
Vol 32 (2) ◽  
pp. 81
Author(s):  
RAFAEL PEREIRA ZANARDI ◽  
SILVIA BEATRIZ ALVES ROLIM ◽  
CLÁUDIO BIELENKI JÚNIOR ◽  
CARLOS ALUISIO MESQUITA DE ALMEIDA

In this work it was analyzed the validation of CBERS-1 (China and Brazillian Earth Resourses Satellite) data related to qualitative and quantitative parameters that define the precision of its georeferencing. A topographical survey was carried out for the acquisition of ground control points spatially well distributed in the study area, employing differential GPS, aiming at the georeferencing of the image. Tests with different numbers of sampling points and several methods of Geometric Transformation and Resampling were made during the georeferencing. These results were statistically analyzed to determine the best method to georeference CBERS-1 images. It was verified that the first-degree polinomial transformation with nearest neighborhood resampling presented the best result, showing a precision of 18,52m.


Author(s):  
Q. Chen ◽  
T. Li ◽  
X. Tang ◽  
X. Gao ◽  
X. Zhang

GF-3 satellite, the first C band and full-polarization SAR satellite of China with spatial resolution of 1 m, was successfully launched in August 2016. We analyze the error sources of GF-3 satellite in this paper, and provide the interferometric calibration model based on range function, Doppler shift equation and interferometric phase function, and interferometric parameters calibrated using the three-dimensional coordinates of ground control points. Then, we conduct the experimental two pairs of images in fine stripmap I mode covering Songshan of Henan Province and Tangshan of Hebei Province, respectively. The DEM data are assessed using SRTM DEM, ICESat-GLAS points, and ground control points database obtained using ZY-3 satellite to validate the accuracy of DEM elevation. The experimental results show that the accuracy of DEM extracted from GF-3 satellite SAR data can meet the requirements of topographic mapping in mountain and alpine regions at the scale of 1 : 50000 in China. Besides, it proves that GF-3 satellite has the potential of interferometry.


Sensors ◽  
2018 ◽  
Vol 18 (11) ◽  
pp. 4023 ◽  
Author(s):  
Guo Zhang ◽  
Qingwei Wu ◽  
Taoyang Wang ◽  
Ruishan Zhao ◽  
Mingjun Deng ◽  
...  

The Gaofen-3 (GF-3) satellite is the first C-band multi-polarization synthetic aperture radar (SAR) with the ability of high-accuracy mapping in China. However, the Ground Control Points (GCPs) are essential to ensure the accuracy of mapping for GF-3 SAR imagery at present. In this paper, we analyze the error sources that affect the geometric processing and propose a new block adjustment method without GCPs for GF-3 SAR imagery. Firstly, the geometric calibration of GF-3 image is carried out. Secondly, the rational polynomial coefficient (RPC) model is directly generated after the geometric calibration parameters compensation of each image. Finally, we solve the orientation parameters of the GF-3 images through DEM assisted planar block adjustment and conduct ortho-rectification. With two different imaging modes of GF-3 satellite, which include the QPSI and FS2, we carry out the block adjustment without GCPs. Experimental results of testing areas including Wuhan city and Hubei province in China show that the geometric mosaic accuracy and the absolute positioning accuracy of the orthophoto are better than one pixel, which has laid a good foundation for the application of GF-3 image in global high-accuracy mapping.


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