Calculating the time difference seems simple, but there are many knowledge points to master. The students who will meet will naturally, the students who will not be really ignorant, many students not only can not remember the latitude and longitude, but also always calculate the time backwards. So today I will focus on explaining the knowledge points and tips of this part of the jet lag to help you overcome the difficulty of jet lag!
01 The foundation of latitude and longitude should be solid
If you want to do a good job of time difference, remembering the latitude and longitude is the key. After each country and each state knows where the approximate latitude and longitude are, it can be calculated according to the latitude and longitude.
The Earth is an irregular sphere with slightly flattened poles and slightly bulging equator.
Equatorial Radius: 6378km
Polar radius: 6357km
Equatorial circumference: about 40,000 km
Second, the meridian
1. Definition of meridians: The lines that connect the north and south poles on the globe and are perpendicular to the parallels are called meridians, also known as meridians.
2. Symbols: East (E), West (W), such as 90°W, 120°E.
3. Features: Shape: semicircle, not parallel, all converged in the north and south corners.
4. Direction: Indicates the north-south direction.
5. Length: All meridians are equal in length, and the latitude of the same meridian is one degree apart by 111 kilometers.
6. Substance: The angle between the local meridian plane and the prime meridian plane (two-sided angle).
7. Special meridian: 0°20°W-160°E180°.
8. Honhatsu Meridian
The prime meridian is the zero-degree meridian on Earth, the starting point for calculating the longitude of the Earth's east-west longitude, divided into 180 points from east to west, and it is the standard reference meridian used to determine the longitude of the Earth and the global moment.
From the prime meridian to the east to the west 180°, along the direction of the Earth's rotation is the east longitude, and the smaller and smaller is the west longitude.
3. Parallels
1. Definition of the latitude line: On the globe, along the east-west direction, a circle around the globe.
2. Symbols: North latitude - "S", south latitude - "N".
3. Calculation of the length of the parallel
A. The longitude difference between the equator is one degree, and the distance difference is 111 km.
B. The arc length of the longitude difference l° on any one line of latitude is about 111 km×cosφ (φ refers to the latitude of the found parallel line). The length of the 60° north-south parallel is half that of the equator.
4. Division of latitudes
5. Latitude essence: The line angle from the local point to the center of the sphere and the line of the equator plane.
6. Latitude judgment: The degree is getting bigger and bigger to the north is the north latitude, and the degree is getting bigger and bigger to the south is the south latitude.
Fourth, the longitude and latitude corresponding to the region
1. The latitude and longitude corresponding to each section
2. The latitude and longitude corresponding to each region of China
02 The law and algorithm of three kinds of time difference problems
1. Calculation of local time topics
1. Concept of local time: Different moments occur due to different longitudes, which are called local time. The longitude varies by 1 hour every 15°, and the local time difference is 1 hour. The longitude difference is 1°, and the local time difference is 4 minutes. Everywhere on the same meridian, the place is the same.
2. Calculation steps
(1) Seek the longitude difference. Follow the principle of "same subtraction and different addition", that is, the longitude is the same as the east or west longitude, and the longitude difference is greatly reduced; If the longitude of the two places - east and west - the difference in longitude is the sum of the longitude of the two places.
(2) When a certain place is located = 4 minutes of soil at a known place / 1 ° X the longitude difference between the two places. The choice of addition and subtraction symbols here follows the principle of "East Plus West Minus". That is, the requested place is added to the east of the known place, and vice versa is subtracted. If the result is > 24, 24 is subtracted, the date is added 1, and if the result is < 0, 24 is added, and the date is subtracted by 1.
2. Calculation of time-related topics
1. Zone time concept
The world is divided into 24 time zones by longitude, and within a certain regional range, the time of uniform use is called the time of the zone, and the zone time is also called the standard time.
(Time Zone Floor Plan)
(North Pole Overlook Time Zone Map)
(1) Find the longitude difference (same subtraction and different addition).
(2) Time zone difference = longitude difference of 115° (rounded).
(3) Zone time difference = Time zone difference X 1 hour.
(4) Time in a certain region = known local time difference (East plus West minus).
(Calculation when "same subtraction and different addition", "East plus West minus", "East-west orientation", and "result processing" in the zone time calculation are all the same place)
3. Calculation of the topic of the crossing of the sun boundary line
1. The concept of the daily boundary line
In order to avoid confusion in dates, the International Longitude Conference of 1884 established an international date change line. This line of change is located on the 180° meridian in the Pacific Ocean and serves as the dividing line between "today" and "yesterday" on Earth, hence the name "International Date Change Line".
To avoid the existence of two dates in a country at the same time, the date line is not a straight line, but a polyline. It stretches from the North Pole in the north, through the Bering Strait, the Pacific Ocean, and up to the South Pole. In this way, the daily boundary line no longer crosses any country. The midnight on this line, that is, the local time zero, is the demarcation time of the date. According to the regulations, whenever this line of change is crossed, the date is changed: when the line is crossed from east to west, the date is added by one day, and when the line is crossed from west to east, the date is subtracted by one day.
(1) The number of time zones separated = (12-Donglai District) + (2-a West Market Area).
(2) Zone time difference = time zone difference X 1 hour.
(3) Time in a certain region = time difference between the earth and the soil in the known place (east minus west plus, east crossing date minus 1 day, west crossing date plus 1 day).
03 Some practical tips
First, use the good arc and the bad arc to judge the east-west direction
1. Both places are in the eastern hemisphere, with the smallest degree in the west and the largest degree in the east.
2. Both places are the same western hemisphere, and the degree of the degree of the degree is the east, and the degree of the degree is the west of the question.
3. Both places are inferior arcs in the same hemisphere.
4. The two places are not in the same hemisphere, and the degrees of the two places are added together, less than 180 degrees is the inferior fox, in the western hemisphere is the west, in the eastern hemisphere is in the east, greater than 180 °, then on the contrary, the genus in the western hemisphere is the east, and the genus in the eastern hemisphere is the west.
Second, the time difference recipe
(1) The calculation of local time follows the "East Plus West Minus".
(2) The calculation of the date, when the international daily boundary line is crossed, the date is spanned from west to east, the date is minus one day; the right east to west spans, and the date is added to one day.
(3) The direction of the Earth's rotation: from west to east, above the North Pole is counterclockwise, above the South Pole is clockwise (north and south).
Source | Network synthesis
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