Satellite Surveying and Mapping Application Center

Beijing, China

Satellite Surveying and Mapping Application Center

Beijing, China
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Tang X.,Satellite Surveying and Mapping Application Center | Zhu X.,Satellite Surveying and Mapping Application Center | Zhu X.,Wuhan University
International Archives of the Photogrammetry, Remote Sensing and Spatial Information Sciences - ISPRS Archives | Year: 2017

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.

Yue Q.,Satellite Surveying and Mapping Application Center | Tang X.,Satellite Surveying and Mapping Application Center | Gao X.,Satellite Surveying and Mapping Application Center
International Archives of the Photogrammetry, Remote Sensing and Spatial Information Sciences - ISPRS Archives | Year: 2017

GF-7 satellite is a two-line-array stereo imaging satellite for surveying and mapping which will be launched in 2018. Its resolution is about 0.8 meter at subastral point corresponding to a 20km width of cloth, and the viewing angle of its forward and backward cameras are 5 and 26 degrees. This paper proposed the imaging simulation method of GF-7 stereo images. WorldView-2 stereo images were used as basic data for simulation. That is, we didn't use DSM and DOM as basic data (we call it "ortho-to-stereo" method) but used a "stereo-to-stereo" method, which will be better to reflect the difference of geometry and radiation in different looking angle. The shortage is that geometric error will be caused by two factors, one is different looking angles between basic image and simulated image, another is not very accurate or no ground reference data. We generated DSM by WorldView-2 stereo images. The WorldView-2 DSM was not only used as reference DSM to estimate the accuracy of DSM generated by simulated GF-7 stereo images, but also used as "ground truth" to establish the relationship between WorldView-2 image point and simulated image point. Static MTF was simulated on the instantaneous focal plane "image" by filtering. SNR was simulated in the electronic sense, that is, digital value of WorldView-2 image point was converted to radiation brightness and used as radiation brightness of simulated GF-7 camera. This radiation brightness will be converted to electronic number n according to physical parameters of GF-7 camera. The noise electronic number n1 will be a random number between - Vn and Vn. The overall electronic number obtained by TDI CCD will add and converted to digital value of simulated GF-7 image. Sinusoidal curves with different amplitude, frequency and initial phase were used as attitude curves. Geometric installation errors of CCD tiles were also simulated considering the rotation and translation factors. An accuracy estimate was made for DSM generated from simulated images.

Wang M.,Hubei University | Hu F.,Satellite Surveying and Mapping Application Center | Li J.,University of Waterloo
ISPRS Journal of Photogrammetry and Remote Sensing | Year: 2011

This paper presents a practical epipolarity model for high-resolution linear pushbroom satellite images acquired in either along-track or cross-track mode, based on the projection reference plane in object space. A new method for epipolar resampling of satellite stereo imagery based on this model is then developed. In this method, the pixel-to-pixel relationship between the original image and the generated epipolar image is established directly by the geometric sensor model. The approximate epipolar images are generated in a manner similar to digital image rectification. In addition, by arranging the approximate epipolar lines on the defined projection reference plane, a stereoscopic model with consistent ground sampling distance and parallel to the object space is thus available, which is more convenient for three-dimensional measurement and interpretation. The results obtained from SPOT5, IKONOS, IRS-P5, and QuickBird stereo images indicate that the generated epipolar images all achieve high accuracy. Moreover, the vertical parallaxes at check points are at sub-pixel level, thus proving the feasibility, correctness, and applicability of the method. © 2011 International Society for Photogrammetry and Remote Sensing, Inc. (ISPRS).

Jiang Y.-H.,Wuhan University | Zhang G.,Wuhan University | Tang X.,Satellite Surveying and Mapping Application Center | Li D.,Wuhan University | Huang W.-C.,Wuhan University
IEEE Transactions on Geoscience and Remote Sensing | Year: 2014

Ziyuan1-02C (ZY1-02C) was launched on December 22, 2011, and it is the first civilian high-resolution remote sensing satellite in China. However, the limited precision of the onboard attitude measurement system causes many errors during attitude transfer by ZY1-02C. Thus, there are complex distortions in the images obtained by ZY1-02C, which restricts its application greatly. In this paper, we consider the feasibility of attitude error correction based on parallel observations with high-resolution cameras, and the method is described in detail. To validate the efficiency of the proposed method, several images and corresponding control data were collected from the Henan, Taihang Mountain, Neimeng, and Taiyuan areas in China. The experimental results indicate that seamless mosaic images without distortion can be obtained using our method. Furthermore, the positioning accuracy with a few ground control points (GCPs) was shown to be better than 1.5 pixels and equivalent to the accuracy of the GCPs. © 2014 IEEE.

Zhang G.,Wuhan University | Zhang G.,Satellite Surveying and Mapping Application Center | Li Z.,Wuhan University | Zhu X.,Satellite Surveying and Mapping Application Center | Fei W.,Wuhan University
International Journal of Image and Data Fusion | Year: 2013

SAR Geocoded Ellipsoid Corrected (GEC) imagery is often taken as a post product processed from slant or ground range radar images. However, its geometric specific, being corrected to a constant ellipsoid height, makes it a coarse geocoded reference for users who are interested in accurate absolute localisation in applications, such as 'ortho-image' generation and digital elevation model (DEM) production. In order to improve the usefulness of SAR GEC imagery, the specific geometric distortions induced by the terrain require corresponding geometric models to perform geometric corrections to the imagery. In this article, both the rigorous physical model and the Rational Polynomial Coefficient (RPC) model for SAR GEC imagery are studied. First, the specific geometry of GEC imagery is illustrated. Then the procedure of reconstructing the rigorous physical model of GECs, which actually is mathematically combined with the normal range-Doppler model, is described in detail. The RPC estimator for replacing this rigorous physical model is then derived. Finally, based on numerous tests with the rigorous physical model available, the modelling error of the RPC is analysed. Four different kinds of high resolution SAR GEC images, i.e. TerraSAR-X, COSMO-SkyMed, RADARSAT-2 and ALOS-PALSAR, are used as experimental data. The experimental results show that using the third-order RPC model with unequal denominators as a substitute for the GEC imaging rigorous physical model, delivers accuracies for different high-resolution SAR GEC images that are all better than 0.01 pixels. The RPC model can be a robust and efficient substitute for the GEC imaging rigorous physical model to perform geometrical processing. © 2013 Copyright Taylor and Francis Group, LLC.

Pan H.,Wuhan University | Zhang G.,Wuhan University | Tang X.,Satellite Surveying and Mapping Application Center | Li D.,Wuhan University | And 3 more authors.
Photogrammetric Engineering and Remote Sensing | Year: 2013

The ZiYuan-3 satellite allows users to obtain triplet along-track stereo and four-band multispectral images within a single pass. Its basic sensor-corrected products are generated by reimaging with a virtual CCD array in which inner and exterior distortions are resolved and the introduced errors are negligible. In this study, three Z Y- 3 datasets (Dengfeng, Anping, and Taihang) were used to evaluate the accuracy of bundle adjustment using triplet stereo images. For both standard and long-strip scenes, the RMS errors of plane and elevation were 2.6 m and 1.6 m, respectively, when ground control points (GCPS) were deployed around the corners. The digital surface model (DSM) of the Dengfeng dataset was compared with a reference DEM (1:2000); the RMS errors produced varied with topography, with values of 3.9 m, 6.4 m, and 6.8 m for plain, hilly, and steep mountainous areas, respectively. © 2013 American Society for Photogrammetry and Remote Sensing.

Huang X.,Wuhan University | Wen D.,Wuhan University | Xie J.,Satellite Surveying and Mapping Application Center | Zhang L.,Wuhan University
IEEE Geoscience and Remote Sensing Letters | Year: 2014

The first results of multispectral (MS) and panchromatic (PAN) image fusion for the ZiYuan-3 (ZY-3) satellite, which is China's first civilian high-resolution satellite, are announced in this study. To this end, the various commonly used image fusion (pan-sharpening) techniques are tested. However, traditionally, image fusion quality is assessed by measuring the spectral distortion between the original and the fused MS images. The traditional methods focus on the spectral information at the data level but fail to indicate the image content at the information level, which is more important for specific remote sensing applications. In this context, we propose an information-based approach for assessing the fused image quality by the use of a set of primitive indices which can be calculated automatically without a requirement for training samples or machine learning. Experiments are conducted using ZY-3 PAN and MS images from Wuhan, central China. One of the objectives of the experiments is to investigate the appropriate image fusion strategies for the ZY-3 satellite at both the data and information levels. On the other hand, the experiments also aim to reveal the inadequacy of the traditional image quality indices and the advantages of the proposed information indices for describing image content. It is suggested that an appropriate image quality index should take into account the global and local image features at both the data and information levels. © 2013 IEEE.

Jiang Y.-H.,Wuhan University | Zhang G.,Wuhan University | Tang X.-M.,Satellite Surveying and Mapping Application Center | Li D.,Wuhan University | And 2 more authors.
IEEE Transactions on Geoscience and Remote Sensing | Year: 2014

The ZiYuan-3 (ZY-3) remote sensing satellite is China's first civilian high-resolution stereo mapping satellite. Because the interior orientation parameters measured before launch are biased, the multispectral (four-band) images collected by ZY-3 exhibit low-accuracy band-to-band registration, which affects their subsequent applications. This paper presents a valid method for interior orientation determination of the ZY-3 multispectral sensor by determining the look angles of the charge-coupled device arrays for all bands. One band is chosen as the benchmark band, and its interior orientation is determined using the relevant ZY-3 image collected over the calibration field and the corresponding digital orthoimage map and digital elevation model. The remaining bands are then calibrated using the benchmark band as control data. The quality of the calibration is further enhanced by shortening the calibration period and by combining images collected over different calibration fields, which decreases the negative effects of errors in the satellite's attitude and position data. The interior orientation of the multispectral sensor in ZY-3 was determined using data sets taken over two calibration fields, namely, Dengfeng (Henan Province) and Tianjin. Evaluation experiments were performed using ZY-3 multispectral images and ground control points (GCPs) collected over several different periods and areas. The positioning accuracy of the ZY-3 multispectral images with a limited number of GCPs after calibration of the interior orientation was better than 0.3 pixels, and the band-to-band registration accuracy was up to 0.15 pixels. © 1980-2012 IEEE.

Wang M.,Wuhan University | Yang B.,Wuhan University | Hu F.,Satellite Surveying and Mapping Application Center | Zang X.,Wuhan University
Remote Sensing | Year: 2014

On-orbit geometric calibration is a key technology to guarantee the geometric quality of high-resolution optical satellite imagery. In this paper, we present an approach for the on-orbit geometric calibration of high-resolution optical satellite imagery, focusing on two core problems: constructing an on-orbit geometric calibration model and proposing a robust calculation method. First, a rigorous geometric imaging model is constructed based on the analysis of the major error sources. Second, we construct an on-orbit geometric calibration model through performing reasonable optimizing and parameter selection of the rigorous geometric imaging model. On this basis, the calibration parameters are partially calculated with a stepwise iterative method by dividing them into two groups: external and internal calibration parameters. Furthermore, to verify the effectiveness of the proposed calibration model and methodology, on-orbit geometric calibration experiments for ZY1-02C panchromatic camera and ZY-3 three-line array camera are conducted using the reference data of the Songshan calibration test site located in the Henan Province, China. The experimental results demonstrate a certain deviation of the on-orbit calibration result from the initial design values of the calibration parameters. Therefore, on-orbit geometric calibration is necessary for optical satellite imagery. On the other hand, by choosing multiple images, which cover different areas and are acquired at different points in time to verify their geometric accuracy before and after calibration, we find that after on-orbit geometric calibration, the geometric accuracy of these images without ground control points is significantly improved. Additionally, due to the effective elimination of the internal distortion of the camera, greater geometric accuracy was achieved with less ground control points than before calibration. © 2014 by the authors.

Tang X.,Satellite Surveying and Mapping Application Center | Xie J.,Satellite Surveying and Mapping Application Center
International Journal of Digital Earth | Year: 2012

As the important infrastructures for land mapping and resource monitoring, high-resolution remote sensing satellites (HRSS) are urgently demanded for the development of China. In this article, the key technologies of the main HRSS are summarized, and these technologies include sensor design, attitude and orbit determination, geometric calibration, imaging model construction, and block adjustment, etc., which involve the mapping accuracy of HRSS. Finally, the system design of the ZY-3 Satellite (China's first civil stereoscopic surveying and mapping satellite, to be launched in 2012) is introduced, which mainly include satellite technical specifications and strategies design based on these key technologies research. © 2012 Taylor and Francis Group, LLC.

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