How to judge the vernal equinox and winter solstice in geographical illustrations?

1. In the bisector, a straight line can be connected between the two spherical centers of the sun and the earth. The intersection of this straight line and the earth's ground is the direct point of the sun, and its position can be judged. It is the summer solstice of the Tropic of Cancer, the winter solstice of the Tropic of Cancer, and the vernal equinox or autumnal equinox of the equator. 2. In the solar illumination map of a single earth, if the solar rays are given, the vertical earth can be found. The intersection of this ray and the ground is the direct point, and the other processes are the same as the above point 1. 3. If the sun's rays are not given, we can also use the day and night conditions in Terminator Trip and Earth to judge the solar terms. Winter solstice occurs when there is an extreme night in the Arctic Circle and its north (or an extreme day in the south of the Antarctic Circle), and summer solstice occurs when there is an extreme day in the Arctic Circle and its north (or an extreme night in the south of the Antarctic Circle). If the global day and night are equal, it means that the terminator line is also in the same position.