Geometric calibration method of all-sky imager based on gradient descent method

Abstract

The embodiment of the invention discloses a geometric calibration method of an all-sky imager based on a gradient descent method. The geometric calibration method comprises the following steps: selecting a target star point in an all-sky image, and determining star point position coordinates of the target star point in an all-sky image coordinate system and a real azimuth angle and a real zenith angle of the target star point at an aurora observation station at the moment of the all-sky image; constructing an error function based on the real azimuth angle and the zenith position and the geographic orientation in the all-sky image, and determining a real zenith position and a real geographic orientation according to the error function; and determining the imaging radius of the target star point according to the star point position coordinates and the real zenith position, and obtaining the relation between the imaging radius and the real zenith angle in the all-sky image through fitting according to the real zenith angle and the imaging radius. According to the technical scheme of the embodiment of the invention, geometric calibration can be quickly and accurately carried out on the all-sky imager without being limited by regions, and the geometric calibration of the all-sky imager is more flexible.

Description

technical field [0001] Embodiments of the present invention relate to the technical field of geometric calibration, and in particular to a geometric calibration method for an all-sky imager based on a gradient descent method. Background technique [0002] The all-sky imager is an important ground-based space environment optical observation equipment. The accurate "object image" optical geometric correspondence is to obtain the actual scale of the auroral structure, determine the projection transformation of the all-sky aurora image to geographic and geomagnetic coordinate systems, and realize The basis for joint observations of all-sky imagers and satellites, which is extremely important for the study of related space physical processes and mechanisms. [0003] The traditional geometric calibration method of the all-sky auroral imager needs to use special calibration equipment under laboratory conditions to take pictures of specific landmarks by rotating the all-sky camera, ...

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Problems solved by technology

[0003] The traditional geometric calibration method of the all-sky auroral imager needs to use special calibration equipment under laboratory conditions to take pictures of specific landmarks by rotating the all-sky camera, and to obtain the relationship between the imaging radius and the zenith angle by fitting. relationship, the above geometric calibration method cannot determine the pixel position and geographic orientation information of the zenith in the all-sky image

In addition, during the actual use of the all-sky imager, due to imaging firmware (CCD, etc.), update of the optical lens, and equipment maintenance, the "object-image" relationship of the all-sky imager will change. For an all-sky auroral imager in the Arctic and Antarctic regions, for example, it is very difficult to recalibrate in the laboratory

On the other hand, in the existing geometric calibration method of the all-sky auroral imager based on star points, it is necessary to manually calculate the position of the zenith in the whole-sky image, and the process is complicated. Due to accidental errors, the number of star points used in fitting the relationship between imaging radius and zenith angle is small, and it is difficult to ensure high accuracy

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