Because many books and video materials for survival (including Bell's talk of this technique) have mentioned that you can use the watch to identify the direction, this method is known as the magic of the rivers and lakes, as if there is a watch, to distinguish the direction that is divided Every minute of the time, talking to other people is always a matter of skill. However, this is purely funny! The principle of using the watch to distinguish directions:
Because of the rotation of the earth, we see that the sun moves 24 hours a day from east to west in the sky. This is called "Sunday Vision Movement" in astronomy. It is stipulated that the time when the sun passes through the upper center of heaven, which is the top of the head, is 12 o'clock. So in our opinion, the sun's path of Sunday vision is like a 24-hour dial, which together with the sun constitutes a huge "natural clock" where the sun is located. And the "dial" is fixed relative to the observation point, and the dial always points to the south.
If the watch also uses a 24-hour clock, the clockwise direction of the watch is aligned with the clockwise direction of the natural clock (ie, the direction of the sun) at any time. Of course, the 12 points on the dial also point to the south. However, the actual use of the watch dial is 12-hour, so we need to perform a mathematical conversion, "half the time" is to convert the dial scale into 24 hours, converted to 12 points after the conversion to the north.
According to this principle, there are two ways to use the watch to identify the direction:
one,
Time is half of the sun, and 12 points is north. Taking 14 o'clock in the afternoon as an example, 14/2=7 and 7 o'clock are aligned with the sun. At this time, the 12 o'clock position is the north.
two,
When the hour hand points to the sun, the angle bisector of the hour hand and the 12 o'clock direction points to the south, and the reverse extension line points to the north. Taking 14 o'clock in the afternoon as an example, the 14 o'clock hour point is aimed at the sun. At this time, the 1/2 direction of the angle between 12 o'clock and 12 o'clock is southward.
Although this method is widely circulated, it is not advisable and the error is so great that it can only be used within the limited time range of high latitudes. Errors in the mid-latitude area can be as high as 20 degrees. The error in the area south of the Tropic of the North can be as high as 50°! This is bad to the horizon, who knows who to use!
Why is there such a big error? It mainly depends on the following reasons:
1. When the time is halved, the singular will not be divisible. If there is a remainder, it will not be counted, only the integer; or when facing the sun, you will ignore the remaining time. Most of the time, you don't tell the direction when you are on the hour. The remaining minutes will be ignored. These are the factors that cause errors.
2. When the direction of watch identification requires the use of a place, the general instruction time is the legal time, not the actual local time of the place. It is Beijing time that we use in China, but China has crossed 5 time zones from the east five districts to the east nine districts. The error in the middle is quite exaggerated. How many people will correct or extrapolate real places based on their longitude?
3. The watch is required to be parallel to the ground, but only on the polar ground, the sun will be parallel to the ground when it is running in the sky. In other places, the sun and the horizon will always have an angle, especially on the equator. They are perpendicular to each other. This is why high latitudes are relatively accurate, and the reason why this method cannot be used at the equator.
4. Finally, with this method, it is necessary to note that before 6 o'clock, after 18 o’clock, the direction of the indication is the opposite of the normal use. How many people have noticed this?
In summary, the use of the watch to identify the direction is actually a very funny thing, first, the error is too alarming, and second, it is completely unnecessary, the sun from east to west, 15 degrees per hour, according to the time correction so the latitude because of the Earth’s revolution It is easy to know the direction from the angle of production.
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