- 标题
- 摘要
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- 实验方案
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Sky camera geometric calibration using solar observations
摘要： A camera model and associated automated calibration procedure for stationary daytime sky imaging cameras is presented. The specific modeling and calibration needs are motivated by remotely deployed cameras used to forecast solar power production where cameras point skyward and use 180° fisheye lenses. Sun position in the sky and on the image plane provides a simple and automated approach to calibration; special equipment or calibration patterns are not required. Sun position in the sky is modeled using a solar position algorithm (requiring latitude, longitude, altitude and time as inputs). Sun position on the image plane is detected using a simple image processing algorithm. The performance evaluation focuses on the calibration of a camera employing a fisheye lens with an equisolid angle projection, but the camera model is general enough to treat most fixed focal length, central, dioptric camera systems with a photo objective lens. Calibration errors scale with the noise level of the sun position measurement in the image plane, but the calibration is robust across a large range of noise in the sun position. Calibration performance on clear days ranged from 0.94 to 1.24 pixels root mean square error.
关键词： fisheye lens,geometric calibration,camera model,sky camera,solar observations,solar power forecasting
更新于2025-09-23 15:23:52
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A Novel Method for Digitalisation of Test Fields by Laser Scanning
摘要： In this article, a novel, media undisruptive method for the measurement of photogrammetric test fields using a laser tracker is presented. The new approach is precise and versatile in its application. It relies on image processing on the quasi continuous measurements of a hand-held laser scanner and laser tracker combination. The field of useful applications is large. In this article, we show the benefit in the field of camera calibration. Essential for highly accurate photogrammetric measurements is a careful calibration, since all cameras have optical distortions due to manufacturing processes of the lens. The calibration can be done by e.g. using a test field. In some cases, 3D coordinates of the control points are necessary. These coordinates are often determined by photogrammetry itself and tacheometric angle measurements in advance. A scale, e.g. a subtense bar, usually needs to be included which increases the measuring efforts. The method bases on the measured 3D point cloud of a test field. With this technique, not only the centers of all control points are accessible. Other geometric features can be chosen too. Since the point cloud consist of many single point measurements, every control point determination has already a high statistical redundancy. The 3D coordinates of every single control point are extracted from the point cloud, making an additional scale obsolete. Presently, the position accuracy is ≤ 50 μm (MPE), which is mainly limited by the laser scanner used in this article. The here-presented technique can be applied to all kinds of shapes, dimensions, materials, numbers and arrangements of control points. Furthermore, it is a lot faster and easier to handle than the angle measurements of the tacheometer.
关键词： Laser scanning,Photogrammetric calibration,Test field,Geometric calibration,3D point cloud
更新于2025-09-12 10:27:22
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[IEEE IGARSS 2019 - 2019 IEEE International Geoscience and Remote Sensing Symposium - Yokohama, Japan (2019.7.28-2019.8.2)] IGARSS 2019 - 2019 IEEE International Geoscience and Remote Sensing Symposium - A Rigorous on-orbit Geometric Calibration Method for High-Resolution Optical Sensor of Chinese Mapping Satellite
摘要： Internationally, the technology of optical earth observation satellite is developing in the direction of miniaturization, high-resolution and high maneuverability. High-precision on-orbit geometric calibration of the imaging sensors is the most important guarantee of interior geometric quality and direct positioning accuracy of the satellite images. The high-resolution camera of Chinese Mapping Satellite-1 is a multi-chip TDICCD optical sensor in triangular mechanical staggered stitching structure. To improve the accuracy and robustness of its geometric calibration while reducing the correlation between calibration parameters, this paper proposed a new multi-chip pointing angle model for internal calibration and an optimized imaging model for external calibration. The overlapping connection relation between multi-chip TDICCDs of an image and multi-scene images are fully utilized for constructing the calibration error equations with constraints. Then, the internal and external calibration are iteratively solved through relaxation block adjustment method. Experimental results demonstrate that the proposed rigorous on-orbit geometric calibration method can effectively and stably eliminate various system errors of the imaging system, thus improving the interior and exterior geometric quality of image production.
关键词： high-resolution satellite image,TDICCD optical sensor,quality evaluation,Geometric calibration
更新于2025-09-12 10:27:22
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Block Adjustment without GCPs for Chinese Spaceborne SAR GF-3 Imagery
摘要： 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.
关键词： RPC,without GCPs,GF-3,accuracy,geometric calibration,planar block adjustment
更新于2025-09-10 09:29:36