【The movement of the earth】
1. The Earth and Globe
【Key Points Summary】
1. Shape and size of the Earth
(1) Shape: An irregular sphere with slightly flattened poles and slightly bulging equator
(2) Size: average radius – 6371 km, equatorial radius – 6378 km, polar radius – 6357 km; equatorial circumference 40,000 kilometers (sitting on the ground and traveling 80,000 miles a day).
Note: Calculation issues of length and radius of any latitude line
If the longitude differs by 1º on the equator, the corresponding arc length is 111km. Similarly, on all longitudes, the arc length of 1º is also 111km. This principle can be used to calculate the actual distance between two points on the earth's surface. The length of 1º arc on the latitude line a is 111cosa.
2. Globe: The earth is reduced to make a model called a globe.
(1) Earth's axis: Turn the globe and you can see that the globe is rotating around an axis. This axis represents the Earth's axis of rotation, the Earth's axis, which always points near the North Star.
(2) North Pole and South Pole: The earth's axis passes through the center of the earth and intersects with the earth's surface at two points. The point pointing toward the North Star is called the North Pole, and the point opposite the North Pole is called the South Pole.
3.Weft line
Definition: On the globe, the circle surrounding the planet Earth in the east-west direction is called a latitude.
Characteristics: ① Except for the poles, all latitude lines are circles and can be called latitudinal circles; ② They gradually shorten from the equator to the north and south poles
Special weft:
Equator: 0º; Tropic of Cancer: 23º26′N; 23º26′S; South and Arctic Circles: 66º34′N; 66º34′S; Low latitudes, middle latitudes and high latitudes: low latitudes (0º-30º), middle latitudes (30º—60º), high latitude (60º—90º)
Function: The latitude line indicates the east-west direction. Determining the east-west direction according to the latitude line is relative. Theoretically speaking, there is no easternmost point or the westernmost point on the earth. Only when the two points are compared can there be distinction between east and west.
4.Latitude
Definition: Calibrating different degrees to latitude lines is latitude.
Determination of latitude: The equator is the zero degree latitude on the globe. Latitudes north of the equator are northern latitudes, and latitudes south of the equator are southern latitudes.
The geometric meaning of latitude: R is the radius of the earth, and the degree of latitude m is α.
Division of the Northern and Southern Hemispheres: North of the equator is the Northern Hemisphere, south of the equator is the Southern Hemisphere
5.Longitude
Definition: On the globe, a line connecting the north and south poles and perpendicularly intersecting the parallels.
Features: ① All meridians are semicircles; ② The lengths are equal
Special longitude: 180º; 0º; 20ºW; 160ºE
Function: Longitude indicates the north-south direction. Determining the north-south direction according to the longitude is absolute. The North Pole is the northernmost point on the earth, and it is surrounded by the south in all directions. On the contrary, the Antarctic is the southernmost point on the earth, and it is surrounded by the north in all directions.
6.Longitude
Determination of longitude: First determine the 0º longitude, which is the prime meridian, and then take the prime meridian as the center to the east and 180º to the west. Longitude increases from west to east to east longitude, conversely, longitude decreases from west to east to west longitude.
Division of the Eastern and Western Hemispheres: (As shown below – top view of the Northern Hemisphere polar area)
The two opposing longitudes 20ºW and 160ºE can form a large circle, called a meridian loop. It is customary to use the 20ºW and 160ºE meridian loops as the boundary between the eastern and western hemispheres. From 20ºW east to 160ºE is the Eastern Hemisphere, and from 20ºW west to 160ºE is the Western Hemisphere.
7. Jingwei network and its functions
Grapitude and latitude mesh: A grid composed of interlaced warp and latitude threads.
effect:
①It is to determine the position of any point on the earth's surface. To determine the geographical location, we must not only look at longitude and latitude, but also correctly distinguish between east longitude and west longitude, south latitude and north latitude.
② Determine the relative direction and distance between various points.
Determination of relative direction: First determine the geographical location, and then determine the combined direction based on east-west longitude and north-south latitude.
Note: The determination of the east-west direction must be based on the minor arc, that is, the longitude interval between the two locations is less than 180º. The specific steps are as follows:
(1) To determine the direction on a latitude and longitude map that is in a grid shape or approximately a grid shape or has a large change in the shape of the latitude and longitude lines, the following steps can be used: First, clarify the north and south latitudes and east and west longitudes based on the numbers on the latitude and longitude lines; secondly, The latitude value that increases toward the south is south latitude, and the direction is south, the one that increases north is north latitude, and the direction is north, the longitude value that increases eastward is east longitude, and the direction is east, and the longitude value that increases toward the west is west longitude, and the direction is west; Again, determine the direction based on north-south latitude and east-west longitude.
(2) To interpret the direction on the latitude and longitude map centered on the pole, the steps are: first, according to the direction of rotation from west to east (known conditions), determine whether the center of the map is the North Pole or the South Pole; second, according to the north and south poles 91exam.org, draw the direction of the Earth's rotation on the edge of the picture; third, the direction pointed by the arrow is the east planet Earth , and the direction of the arrow tail is west.
Figure (a) is a fan-shaped longitude and latitude grid. The arrows are in the southern hemisphere, so the "clockwise" direction is the east, so 2 is to the east of 1, 2 and 3 are on the same longitude line, 2 To the north of 3.
Picture (b) shows the rotation of the earth from above the North Pole. If the arrow is reversed, then the direction along the "counterclockwise" is east, so 6 is to the east of 4, 5 is to the northeast of 4, and 5 is to the northwest of 6. square.
Figure (c) is a latitude and longitude map centered on the South Pole. 7 is directly west of 9 and 7 is northwest of 8.
(3) Judgment of direction on a map without latitude and longitude lines
(4) Calculate distance using graticule
① On the same meridian, the arc length spanning 1° of latitude is approximately 111km.
②For the planet Earth at the equator, the arc length across 1° of longitude is approximately 111km; at any latitude, the arc length across 1° of longitude is approximately 111km×cosa
(aThe geographical latitude of the place).
③ Antipodal point: A point of symmetry on the earth's surface with respect to the center of the earth. The latitude values of these two points are equal, but the north and south are opposite; the longitudes of the two points must form a meridional circle, that is, the sum of the longitudes is equal to 180°, but the east and west longitudes are opposite.
(5) Estimation of the shortest distance between two points on different longitude and latitude lines
The great circle passing through two points is not a meridian coil, but a great circle with the center of the earth as the center and an oblique intersection with the meridian coil.
(6) Judgment of the nearest route direction between the two places
The shortest distance between any two points on the sphere should be the length of the minor arc of the great circle passing through the two points.
