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EP-3978869-B1 - INFORMATION PROCESSING SYSTEM, METHOD, AND PROGRAM

EP3978869B1EP 3978869 B1EP3978869 B1EP 3978869B1EP-3978869-B1

Inventors

  • TAKASHIMA, Yuya
  • MINOWA, MASAHIRO
  • OKUMURA, Shigeaki

Dates

Publication Date
20260506
Application Date
20200422

Claims (7)

  1. An information processing device (1), comprising: an image acquisition module (11) configured to acquire an image (G1, G4) obtained by photographing the sky with a camera (10) having a known slant, the slant expressed by a roll angle and a pitch angle with respect to a roll axis and a pitch axis orthogonal to each other in a horizontal plane; a photographing time stamp acquisition module (12) configured to acquire a photographing date and time of the image (G1, G4); a photographing position acquisition module (13) configured to acquire position information of a photographing position of the image (G1, G4); a sun position determination module (14) configured to determine a photographed sun position (S1) indicating a sun position in the image (G1, G4); a reference sun position acquisition module (15) configured to calculate a reference sun position (B1) indicating a position of the sun determined based on the photographing date and time and the position information; and a camera information identification module (17) configured to determine the unknown orientation of the camera (10) based on the known slant of the camera (10), the photographed sun position (S1), and the reference sun position (B1), the unknown orientation expressed by a yaw angle with respect to a yaw axis parallel to a vertical direction, wherein: the camera information identification module (17) compares the photographed sun position (S1) with the reference sun position (B1) by using the slant of the camera (10) to determine the unknown orientation of the camera (10), wherein: the image acquisition module (11) acquires a plurality of images (G1, G4); and the camera information identification module (17) determines the unknown orientation of the camera (10) by using an average of a difference between a photographed sun position (S1) and the reference sun position (B1) in the plurality of images (G1, G4).
  2. The information processing device (1) according to claim 1, wherein: the image (G1, G4) is a whole-sky image captured by a whole-sky camera; the reference sun position (B1) indicates the sun position in the whole-sky image when the camera (10) is horizontal and the camera (10) is oriented in a predetermined direction; and the camera information identification module (17) determines the photographed sun position (S1) when the camera (10) is horizontal by using the slant of the camera (10), and determines the unknown orientation of the camera (10) by comparing the determined photographed sun position (S1) with the reference sun position (B1), wherein in a horizontal camera, a center (P1) of an image (G1, G4) obtained from the camera (10) has an elevation angle of 90°, with an elevation angle decreasing from the center toward the end of the image (G1, G4).
  3. The information processing device (1) according to claim 1 or 2, further comprising: an image correction module (18) configured to correct the image (G1, G4) acquired by the image acquisition module (11) based on the orientation of the camera (10) determined by the camera information identification module (17) into an image (G3) to be photographed when the camera (10) has a predetermined orientation and a predetermined slant.
  4. The information processing device (1) according to any one of claims 1 to 3, further comprising: an error information output module (19) configured to output error information of the orientation of the camera (10) based on the orientation of the camera (10) determined by the camera information identification module (17).
  5. A computer-implemented information processing method, comprising: acquiring an image (G1, G4) obtained by photographing the sky with a camera (10) having a known slant, the slant expressed by a roll angle and a pitch angle with respect to a roll axis and a pitch axis orthogonal to each other in a horizontal plane; acquiring a photographing date and time of the image (G1, G4); acquiring position information of a photographing position of the image (G1, G4); determining a photographed sun position (S1) indicating a sun position in the image (G1, G4); calculating a reference sun position (B1) indicating a position of the sun determined based on the photographing date and time and the position information; and determining the unknown orientation of the camera (10) based on the known slant of the camera (10), the photographed sun position (S1), and the reference sun position (B1), the unknown orientation expressed by a yaw angle with respect to a yaw axis parallel to a vertical direction, wherein: the information processing method compares the photographed sun position (S1) with the reference sun position (B1) by using the slant of the camera (10) to determine the unknown orientation of the camera (10), wherein: a plurality of images (G1, G4) are acquired; and the information processing method determines the unknown orientation of the camera (10) by using an average of a difference between a photographed sun position (S1) and the reference sun position (B1) in the plurality of images (G1, G4).
  6. The information processing method of claim 5, wherein: the image (G1, G4) is a whole-sky image captured by a whole-sky camera; the reference sun position (B1) indicates the sun position in the whole-sky image when the camera (10) is horizontal and the camera (10) is oriented in a predetermined direction; and the information processing method determines the photographed sun position (S1) when the camera (10) is horizontal by using the slant of the camera (10), and determines the unknown orientation of the camera (10) by comparing the determined photographed sun position (S1) with the reference sun position (B1), wherein in a horizontal camera, a center (P1) of an image (G1, G4) obtained from the camera (10) has an elevation angle of 90°, with an elevation angle decreasing from the center toward the end of the image (G1, G4).
  7. A program comprising instructions, which, when executed by one or more processors, cause the one or more processors to perform the information processing method of claim 5 or 6.

Description

The present disclosure relates to an information processing system (device), method, and program for determining the orientation or slant of a camera used for cloud observation. For conventional cloud observation, satellites are mainly used. Since satellites observe clouds from above, they cannot obtain detailed distribution of clouds near the ground. Therefore, an amount and duration of sunlight on the ground cannot be grasped. As an alternative to satellites, it is known to use a camera such as a whole-sky camera installed on the ground. It is conceivable that the cameras are installed in measurement zones spaced apart from each other and observe the same cloud using images from a plurality of cameras. [Patent Document 1] WO 2010/079557 In such cloud observation by a plurality of cameras, it is necessary that the orientation and slant of each camera coincide with each other with high accuracy. Further, even in the cloud observation by a single camera, if the orientation and slant of the camera do not coincide with each other accurately, an error is included in the orientation of the cloud reflected in the obtained image. If the orientation of the cloud includes an error, it is difficult to obtain a desired accuracy when the solar radiation amount is estimated based on the movement of the cloud by taking in external data such as wind velocity. International Patent Publication No. WO 2010/079557 (Patent Document 1) describes a device for detecting the orientation of a camera, but not a whole-sky camera. However, this method requires a deflection camera. US 2017/0154233 Al likewise describes determining compass orientation of imagery with a horizontally aligned camera used. The paper by Bryan Urquhart et al.: "Sky camera geometric calibration using solar observations", Atmospheric Measurement Techniques, vol. 9, no. 9, 1 January 2016, pages 4279-4294, XP055829269, DOI: 10.5194/amt-9-4279-2016 discloses a device for sky camera geometric calibration using solar observations, wherein information further to the solar observations is assumed to be known. If an attitude sensor or an orientation sensor is mounted, the orientation and slant of the camera can be obtained, but an extra sensor is required. Further, although it is possible to prevent the deterioration of accuracy by carrying out strict orientation alignment and slant alignment when installing the camera, the installation work of the camera becomes troublesome. It is an object of the present disclosure to provide an information processing device, method, and program capable of determining the orientation or slant of a camera while facilitating the installation work of the camera and reducing the number of sensors provided in the camera. The object is solved by the subject-matter of the independent claims. An information processing device according to the present invention includes the features of claim 1. According to a non-claimed example, if any one of the orientation and the slant of the camera is known, any one of the unknown orientation and the unknown slant of the camera can be determined based on the photographing date and time, the position information of the photographing position (for example, latitude and longitude), and the sun position reflected in the image. Therefore, it becomes unnecessary to align the orientation or the slant when the camera is installed, and it becomes possible to specify the slant or the orientation of the camera without providing an attitude sensor or an orientation sensor. In the information processing device, the slant of the camera is known, and the camera information identification module compares the photographed sun position with the reference sun position by using the slant of the camera to determine an unknown orientation of the camera. In the information processing device, the image may be a whole-sky image captured by a whole-sky camera, the reference sun position may indicate the sun position in the whole-sky image when the camera is horizontal and the camera is oriented in a predetermined direction, and the camera information identification module may determine the photographed sun position when the camera is horizontal by using the slant of the camera, and may determine the unknown orientation of the camera by comparing the determined photographed sun position with the reference sun position. In the information processing device, the image acquisition module acquires a plurality of images, and the camera information identification module determines the unknown orientation of the camera by using an average of a difference between a photographed sun position and the reference sun position in the plurality of images. In a non-claimed example of the information processing device, the orientation of the camera may be known, and the camera information identification module may compare the photographed sun position with the reference sun position by using the orientation of the camera to determine an unknown sla