The front buildings are 99M high and 30M apart. Sunlight can also be seen in the winter solstice upstairs in the back row building (Zhengzhou).

Sunlight can also be seen in the winter solstice above the 20 th floor in the back row.

Only the time of sunrise and sunset is not enough, because the trajectory of the sun in the sky rises from the east, and then gradually goes south until noon. After noon, the situation is just the opposite. Even the sun rises from the southeast in winter and from the northeast in summer.

Now we have to work out the solar latitude at each time point. How to calculate this, we didn't expect, but we found a website on the Internet to demonstrate the rise and fall of the sun. From this website, we can roughly calculate the approximate position of the sun in Zhengzhou on the winter solstice, which is the data of the sun position in the first table in this part.

Prepare information and the building spacing, height, floor and width of the building in front. Also pay attention to whether there are side-by-side buildings around the front building, and if so, what is the height. Others should also consider whether there is a heightening decoration or equipment room on the top of the front building. We assume that there is a retaining wall with a height of 1.2 meters at the top of the front building. Also consider whether the vision of the front and rear buildings is highly consistent.