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›› 2019, Vol. 36 ›› Issue (3): 363-375.DOI: 10.7523/j.issn.2095-6134.2019.03.010

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The improvement in solar position calculations in the ellipsoid model of the earth

LI Wen1,2,3, ZHAO Yongchao1,2,3   

  1. 1. Key Laboratory of Technology in Geo-Spatial Information Processing and Application System of CAS, Beijing 100190, China;
    2. Institute of Electronics, Chinese Academy of Sciences, Beijing 100190, China;
    3. University of Chinese Academy of Sciences, Beijing 100049, China
  • Received:2018-01-25 Revised:2018-03-29 Online:2019-05-15

Abstract: Accurate and efficient calculation of the solar position is of great value in the fields of remote sensing radiation calibration and solar energy acquisition. Firstly, in this work we use the numerical fitting method to improve the calculation of the solar declination aiming at solving the problem that the differences in data among different years has not been considered enough in the original algorithms. According to the periodicity represented by the error curves, an improved algorithm for solar declination calculation based on a period of four years is proposed by using the Fourier expansion method. Then the formula of the solar elevation angle under the earth ellipsoid model is derived. Finally, the improved formula of the atmosphere refraction at elevation angles of 0°-30° is proposed to solve the problem of excessive errors of the original algorithms at small elevation angles, because the atmosphere refraction affects the observation and calculation of the solar position. The results show that the algorithms given in this paper significantly reduce the errors in the calculations of the solar declination angle, the solar elevation angle, and the atmosphere refraction at small elevation amgles. The calculation process is simple and efficient, which accords with the requirements of the relevant project.

Key words: ellipsoid model of the earth, solar elevation angle, solar declination, atmosphere refraction

CLC Number: