US 12,352,576 B2
Atmospheric polarized light orientation method using a solar azimuth region
Jun Liu, Taiyuan (CN); Xindong Wu, Taiyuan (CN); Chong Shen, Taiyuan (CN); Huiliang Cao, Taiyuan (CN); Jun Tang, Taiyuan (CN); and Chenguang Wang, Taiyuan (CN)
Assigned to NORTH UNIVERSITY OF CHINA, Taiyuan (CN)
Filed by NORTH UNIVERSITY OF CHINA, Taiyuan (CN)
Filed on Dec. 7, 2023, as Appl. No. 18/531,770.
Prior Publication US 2025/0044096 A1, Feb. 6, 2025
Int. Cl. G01C 21/02 (2006.01); G06T 7/155 (2017.01); G06T 7/187 (2017.01); G06T 7/66 (2017.01); G06T 7/73 (2017.01)
CPC G01C 21/02 (2013.01) [G06T 7/155 (2017.01); G06T 7/187 (2017.01); G06T 7/66 (2017.01); G06T 7/73 (2017.01); G06T 2207/20156 (2013.01)] 9 Claims
OG exemplary drawing
 
1. An atmospheric polarized light orientation method using a solar azimuth region, comprising a computer readable medium operable on a computer with memory for the atmospheric polarized light orientation method, and comprising program instructions for executing the following steps of:
step 1: detecting a four-channel polarization image by utilizing an image polarimeter, and calculating an AOP φm according to the four-channel polarization image;
step 2: obtaining a solar elevation angle and a solar azimuth angle, obtaining an observation point elevation angle and an observation point azimuth angle, converting an AOP in an incident light frame into an AOP in a pixel frame by utilizing a theoretical AOP model of the pixel frame, establishing a theoretical model of the AOP, and ignoring a measured noise, wherein the obtained AOP is the AOP calculated by using the four-channel polarization image, and obtaining a relation between the AOP φpb and the solar azimuth angle Asb through the theoretical model of the AOP;
step 3: extracting the solar azimuth region for the AOP φm by utilizing a region growth model, setting an initial growth point as a principal point of photograph, performing region growth on a current AOP image at the initial growth point, and calculating a grown binary image; and filtering the grown binary image by utilizing the operation of image morphology, calculating a centroid of the filtered binary image, updating a seed line according to the centroid, and taking the updated seed line as an initial growth point of the next frame of AOP image for extracting the solar azimuth region;
step 4: calculating a first approximate solar azimuth angle As,fb according to the updated seed line; along the solar direction, dividing the binary image in the solar direction into image blocks with an equal field of view; and calculating a second approximate solar azimuth angle As,rb by utilizing the image blocks with an equal field of view, wherein all measured solar azimuth angles z are represented as Z=[As,rb, As,fb]; obtaining an optimum estimation Âsb to the solar azimuth angle according to z, wherein

OG Complex Work Unit Math
 is obtained and C is an unsolved value when the Âsb reaches a minimum value;
calculating the horizontal attitude angle by an inertial navigation system, setting an absolute heading angle as ψ, and calculating the absolute heading angle ψ by using the following equation according to all measured solar azimuth angles and their optimum estimations:

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wherein, Asb represents a solar azimuth angle in a body frame;
step 5: improving an orientation accuracy and speed of atmospheric polarized light navigation based on the results of the atmospheric polarized light orientation method.