Mang species points to latitude.

"When heading, the direct point of the sun is at 22 44' north latitude, and the geographical range of Shenzhen is from111/4 37 east longitude, 22 27 to 22 52 north latitude, and the Tropic of Cancer (23 27' north latitude Before and after the awn seed, it is about Beijing time 12:23, and the direct point of the sun is in Shenzhen. At this time, the vertical rod has no shadow. Then the direct point of the sun moves northward, reaches the Tropic of Cancer on the solstice in summer, and returns to Shenzhen latitude around the high temperature in summer.