Study on Positioning Algorithm of Sun Shadow

Sun shadow positioning technology plays an important role in the field of modern communication and monitoring. Aiming at the close relation between shadow length and the date, time, place, object size, this paper studies the sun shadow of straight bar in depth, establishes the following models mainly for the two questions raised, obtains shadow length variation rule over time, and identifies the specific location of the straight bar. In model 1, this paper establishes the geometric model of sun shadow length with respect to straight bar height, solar altitude and azimuth. Mathematical expressions of sun shadow length changes of a certain place with respect to the four parameters of latitude, longitude, Beijing time and date are obtained, and variation rule of shadow length with respect to each parameter can be analyzed according to the expression mapping. Under the condition that the above-mentioned parameters are known, using this model can have MATLAB software drawn the changing curve of shadow length over time. In model 2, this paper establishes a nonlinear fitting model. When the place of shadow is unknown, nonlinear least square method is first applied to conduct second fitting on shadow length and time, thus obtaining the point of the minimum shadow length, Beijing time of the location is determined, the longitude is then determined, and Marquardt nonlinear fitting or differential evolution fitting algorithms and 1 stOpt software are applied for obtaining the latitude. Sun shadow positioning technology can perfectly determine the specific location of the shadow, and this paper has high positioning accuracy in this aspect, which has good use value in the control field of solar energy receiving device.