A server, comprising: a reception unit configured to receive a captured image and information on an image capture date and time and an image capture location from an on-board device that is configured to capture an image of surroundings of a vehicle and to produce the captured image, the surroundings including a sidewalk; a storage unit configured to store brightness information of the sidewalk on the image capture date and time, the brightness information being detected based on the captured image and the image capture location; and a transmission unit configured to send the brightness information to a mobile terminal, characterized in that: the server comprises a brightness information detection unit configured to detect the brightness information of the sidewalk on the image capture date and time based on the captured image and the image capture location, the brightness information containing information on a position of a part of the sidewalk shaded in daytime detected from the captured image; wherein the brightness information detection unit is configured to perform detection of the position of the part that is shaded in the daytime on a condition that the brightness information detection unit detects an image of a person wearing a predetermined tool that is likely to be worn, carried, held, or used when the sun is strong from the captured image. a reception unit configured to receive a captured image and information on an image capture date and time and an image capture location from an on-board device that is configured to capture an image of surroundings of a vehicle and to produce the captured image, the surroundings including a sidewalk; a storage unit configured to store brightness information of the sidewalk on the image capture date and time, the brightness information being detected based on the captured image and the image capture location; and a transmission unit configured to send the brightness information to a mobile terminal, characterized in that: the server comprises a brightness information detection unit configured to detect the brightness information of the sidewalk on the image capture date and time based on the captured image and the image capture location, the brightness information containing information on a position of a part of the sidewalk shaded in daytime detected from the captured image; wherein the brightness information detection unit is configured to perform detection of the position of the part that is shaded in the daytime on a condition that the brightness information detection unit detects an image of a person wearing a predetermined tool that is likely to be worn, carried, held, or used when the sun is strong from the captured image. the server comprises a brightness information detection unit configured to detect the brightness information of the sidewalk on the image capture date and time based on the captured image and the image capture location, the brightness information containing information on a position of a part of the sidewalk shaded in daytime detected from the captured image; wherein the brightness information detection unit is configured to perform detection of the position of the part that is shaded in the daytime on a condition that the brightness information detection unit detects an image of a person wearing a predetermined tool that is likely to be worn, carried, held, or used when the sun is strong from the captured image.