The following is the principle and method of using a watch to identify the direction:
The earth rotates 360 degrees in 24 hours, 1 hour rotation 15 degrees, and the hour hand of a watch is always twice as fast as the sun. According to this principle, the position can be roughly determined by the watch and the sun. At 6 o'clock in the morning, the sun is in the east and the shadow points to the west. At this time, the hour hand on the watch points to the sun, and the word "12" on the dial points to the west. If the dial is rotated by 90 degrees, the 6 o'clock position is half, so that the "3" on the dial faces the sun and the "12" points to the north. At noon, 12, the sun is in the south. If 12 is folded in half so that the character "6" on the dial faces the sun, the character "12" still refers to the north (Figure 6).
According to this method, the local time difference should be considered. Time conversion should be set to local time. Take east longitude 120 degrees as the line, east longitude 15 degrees, Beijing time plus 1 hour, west longitude 15 degrees, and Beijing time minus 1 hour as the local time. If the geographical coordinate of Urumqi is 87 degrees 40 minutes east longitude, then (120-87) ÷ 15 = 2 hours and 9 minutes, Beijing time minus 2 hours and 9 minutes, it is the local time in Urumqi.
Taiwan Province Chiayi, Nan 'ao Island, Guangdong Shantou Northeast, Guangxi Wuzhou, Yunnan Gejiu South of the Tropic of Cancer (23 degrees 27 minutes north latitude) can not use the above two methods in summer.
By the way, we know that the relative position of the earth and the sun has moved 15 during the rotation of the earth, and we can roughly determine the direction with the watch and the sun. On the contrary, we can also use the compass and the sun to measure the approximate time. The method is to point to the north with a compass, and the reading of the sun position can be divided by 15. China is based on Beijing time, Beijing is on the east longitude 120 line, and other areas should be corrected according to the longitude difference, that is, the correct solar time.