A watch, give it to you who can't find the north, help you get the southeast and northwest

When we are in the wild, powerful mobile phones, Beidou satellites, GPS, etc. provide us with quite reliable contact and positioning guarantee. However, there are too many limitations for electronic equipment. When they accidentally strikes for various reasons, can you still tell the southeast and northwest? Try to use astronomical observations to determine the direction!

Let the watch help you find North

In the morning and evening, the sun is the best "pointing light". It is rising to the east every day. For the north hemisphere, the sunrise position in winter is east and south, and the sunset position is south of the south. The sun is in the east, and the sunset is in the west.

When the wild is lost, the watch can be distinguished

However, the easiest time for us to "find the north" is usually not morning and evening or noon, but ninety o'clock in the morning or 3 or four pm. The high and bright sun is at a loss. At this time, please don't forget the watch, it is a weapon that distinguishes the direction. We only need to follow the following steps to operate:

Watch the schematic diagram at 8 am. According to the tactics of "half of the time to the sun", the 4 o'clock scale of the hour hand is aligned with the sun, then the 12 o'clock on the dial is to the north

Put the watch flat, read the time on the watch at 24 o'clock, divide the hourly number to get a number A; then let the A scale on the dial align with The above is the north, and the direction referred to at 6 o'clock is the south. There is a way to make a convenient memory: "The time is half a discount to the sun, and the north is pointing at 12 o'clock." The quasi -sun, then the direction of the dial at 12 points is roughly north.

Where does the distinguishing error come from?

Why use watches and sun to determine the direction? This will start from the time system. The time measuring system originated from astronomical observations. Through the rotation of the earth, that is, the cycle of the celestial bodies rising and falling, it has obtained the concept of "day"; and through the revolving of the earth, that is, the glory of the plants and trees, the changes in the four seasons, especially the height of the sun, the height corner of the sun The periodic changes of the "year" have been obtained. Later, it was divided into time, minute, second. Although modern society is defined in order to meet the needs of more accurate timing, the second length has changed to the atom, the astronomical attributes of time have not changed. The time we use daily, that is, the time on watches and mobile phones, still keeps synchronized with the rotation of the earth, 24 hours a day.

The sun rises from the east in the morning, the highest noon at noon, and it falls from the West at night.

How is the starting point of time defined? It is stipulated that the sun passes through the highest point in the sky in the day, which is 12 noon local time. It can be seen that when the sun rises to the west every day, the path that passes through the day is like a 24 -hour dial. It forms a huge "natural clock" with the sun. It is worth noting that the direction of this "dial" is relatively fixed relative to observation, and at 12 o'clock, it always points to the south of the observation place (in the area north of the north).

Our watches can be regarded as the "miniature" version of this natural clock. In actual life, the watch dials we use are all 12 o'clock, so we need to perform mathematical conversion. "Half of time" is to convert the dial scales to 24 -hour system. After conversion, it becomes 12 o'clock to the north. Because the view of the sun is not regular, there are slight changes every day, so in most days, when the watch is displayed at 12 o'clock, the sun is not at the highest point. However, the maximum difference does not exceed 18 minutes, and the impact on the accuracy of the distinguishing orientation is slightly (not more than ± 5 degrees).

At 4 pm on May 26, 2020, the measurement diagram of the measurement of the law was used to use the level of use. At 8 o'clock in the watch for the quasi -sun. The red arrow marks the actual direction of the south, and the green arrow is a 12 o'clock direction on the dial. Because in the summer, the height of the sun is still relatively high, and the distinguishing error is close to 30 degrees

After understanding the principle, it is easy for us to find that there are two sources of the watch discerning error:

1. Because the position of Beitianji (that is, the point of the earth's rotation) in advance, the dial can only be placed horizontally, and the path that the sun passes through the sky is tilted and not parallel. , The larger the angle (when the geographical latitude is lower), the worse the directional accuracy;

2. The center of the dial and the round surface of the solar video movement only coincides in the two days of spring and autumn. At other times, it will not be rearranged, and it will also bring errors to the distinguishing direction.

Winter and high -latitude accuracy is high, and low latitude must be guarded in summer and low latitudes

The accuracy of the watch direction is related to the local latitude, date, and always. Pay attention to the following points when using:

1. Strictly speaking, the Beijing time displayed on the watch should be converted into a local place. Although it is not necessary to be particularly accurate, it is best to understand that the location is about a few degrees from 120 degrees east, and the principle of "1 degree difference between the longitude and 4 points of time" (Dongjia and West) is estimated in the geography. For example, Xi'an (108.75 degrees east) at about 10 degrees west of Beijing, then the place in Xi'an should be the Beijing time shown by our watch for another 40 minutes. The more you need to pay attention to West Vietnam. For example, in the western part of China, Kashgar and other regions (about 75 degrees east longitude, 40 degrees north latitude). If you do not make time conversion, at 10 am, the error of the watch discerning is up to 70 degrees! In order to reduce the error, it is necessary to convert the time to distinguish it with a watch. 2. Watch dislikes when the height of the sun is relatively low. Before 9 o'clock in the morning and after 3 o'clock in the afternoon, the accuracy is higher, and the accuracy of high latitudes is better than low latitudes. It is important to note that in the summer of low latitudes, due to the large angle of the solar, the error of the watch discerning is often as high as 50 degrees! And if the watches are used in October to April of the following year, the error generally does not exceed 30 degrees.

Overall, the watches are used to distinguish the watches in the northern hemisphere. The accuracy of winter is higher, the spring and autumn are second, and the summer is the worst. Therefore, we might as well add the tactics of the watch to the watch as follows:

The time is half folded to the sun, pointing at the north at 12 o'clock. The accuracy of high latitudes and high latitude is high, and low latitudes must be guarded in summer and low latitudes.

Is it feasible to distinguish vertical direction?

Vertical discrimination to a schematic diagram. After determining the general orientation of the level of the level, the watch is placed vertically in the east -west plane. If it is distinguished at 10 am, you can find that B is equal to 11 according to the calculation in the text. Then keep it vertical, and slightly rotate the watch surface of the watch, so that the scales of the dial up to 11 are aligned with the sun, then the dial is facing the direction of the north at this time

After we understand the principle, it is not difficult to think of, why not try to place the dial vertically? Someone had done computing and experiments, and found that vertically placing dials to distinguish the direction of operation is completely feasible. We summarized the following operations:

First use the horizontal discerning method, and then use the vertical discerning to the diagram of the direction. The shooting direction is Zhengnan, and the red dotted line is the vertical line. The dial is still biased, indicating that the direction of the law line does not point to Zhengbei. However, the accuracy has been greatly improved, and the visual error may be within 10 degrees

First of all, use the level to distinguish the north to the Fa, and then find the general east -west direction, place the watch dial vertically in the east and west directions, and let the disk face the measured north; then read it at 24:00 to read out. At that time, A, and calculated a value B: B = A/2+6 (at the time of A ≤ 12 points), or B = A/2-6 (at the time of A ≥ 12).

The addition or minus here is to satisfy the final number B: 0≤b ≤ 12. For example, observe at 10 am, A is 10, b = a/2+6 = 11; if it is 2 pm, then A = 14, b = a/2-6 = 1. Finally, keep the watch vertically and slightly rotating the dial until the scale B on the watch align the sun. At this time, the direction of the dial is pointing to the north.

During the actual operation, due to the dazzling sunlight, the watch scale is not easy to align the sun. We can find the shade or other reference objects, and use the light that is shot from the gap of the leaves to accommodate. In addition, when the scale is aimed at the sun, the dial is often not in the same plane as the incident sunlight, and pay attention when operating.

Contrary to the level of the level, vertical discerning method is more suitable for the height of the sun, and the accuracy is poor when the solar is low, and it will not be applicable before 6 am or 6 pm You can think about what this is). The combination of the two methods can expand the application range of the watch discerning and improve the directional accuracy. For example, in the summer or from 9 am to 4 pm in the low latitudes area, first use the horizontal discern to get a general direction, and then modify it with vertical discerning to the method to significantly improve the accuracy. Interested readers may wish to try it.

This article comes from the magazine of "Knowledge is Power". The original title "Watch is in hand, I have in the direction", author Li Jian, deleted and modified, please indicate the source of the original work.

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