Learning ideas and methods to present this knowledge, these difficulties will be solved. The author has made some attempts in this respect.
We have received good results and are willing to communicate with our peers.
One,
Direct solar point problem
Because the angle between the earth axis and the ecliptic plane is
six
six
34
′,
The point on the earth's surface that receives vertical sunlight.
(abbreviation
Point of direct sunlight)
Change with time.
From the solstice in winter to the solstice in the following summer,
The direct point of the sun comes from the south latitude.
2
three
26
"direction"
Moving north,
cross the equator
(at the vernal equinox)
Arrive at north latitude
2
three
26
′;
From the solstice in summer to the solstice in winter,
The direct point of the sun comes from the north latitude.
2
three
26
Move south and cross the equator (at the autumnal equinox)
Reach south latitude
2
three
26
The direct point of the sun is in the north-south direction of the equator.
Motion presents a certain periodicity, and a period is called
1
The geographical process of the tropic of cancer hides a problem that is difficult for students to understand.
Problems solved:
Why doesn't the line plane angle formed by the earth's axis and the ecliptic plane of the sun work?
nine
It will lead to the period of direct sunlight.
Transsexualization? Now use mathematical language and graphics to explain and explain this geographical problem:
As shown in figure 1, the earth
Four places in four locations.
axis
four
three
2
1
//
//
//
l
l
l
l
and
Zodiac plane
M
acquire
It's everywhere
six
six
34
′。
Spherical center o
1
O-centered
three
be
On the long axis of the elliptical orbit
Up and down.
A
and
C
That is to say,
The direct point of the sun:
Australian second-class honorary officer
1
A
Degree' is
at this point
A
Geographical latitude of
for
90
-
66
34
′
=
2
three
26
In the same way.
C
It's in the north latitude
2
three
26
, ball o
1
Use the ball
three
The location dates are winter solstice and summer solstice respectively, and the direct points of the sun are respectively
In the south latitude
2
three
26
And north latitude.
2
three
26
′。
It is difficult for students to understand that the earth is in the ball O.
2
Use the ball
four
Why is the direct point on the equator when the sun is in position? this
Time ball o
2
And the equatorial plane of the ball O.
four
The equatorial plane of is on the same plane and is set as a plane.
α
, two parallel straight lines
2
1
l
l
and
real
Fixed plane
β
plane
α
∩ Plane
β
= straight line o
2
O
four
Setting plane
β
The two intersections with two equatorial circles are b,
d，
therefore
four
2
O
O
D
B
D
B
D
B
straight line
、
plane
、
main points
plane
、
main points
,
Point b and point d are the direct points of the sun, which proves that at this time
1
l
2
l
three
l
four
l
O
1
O
2
O
three
O
four
C
B
D
A
'
A
C
'
O
Figure 1
The direct point of the sun is on the equator, and the dates are vernal equinox and autumnal equinox respectively.
Due to the movement of the direct point of the sun, the solar radiation energy received by the earth's surface changes with time and place, resulting in
The alternation of four seasons and the formation of five zones. Students understand this part of the content, which can lay a foundation for students to study geography in the future.
A good foundation.
Second,
Calculation of local time
Because the earth rotates from west to east, in the same latitude area, the relative position of the east is more than that of the west.
Watching the sunrise at 8: 00, the time is divided into early and late, resulting in local time. Local time varies with longitude, so it is not used properly.
As a result, the method of dividing regions according to unified standards has been adopted internationally, so there is a problem of calculating local time and time zone, which is determined by
When the time zone is the central meridian of the time zone, the time zone calculation can also be converted into local time calculation. Through the London courthouse
The meridian of Linwich Observatory is defined as
Meridian, followed by east longitude.
1
east longitude
2
,? Go west in turn.
This is a western classic.
1
,
2
,? It's like the number axis in mathematics. If the east is defined as the positive direction, then the corresponding
The number is a positive real number, and the definition to the west is a negative direction, so the corresponding number is a negative real number, so calculating the longitude tea is to find the number.
The distance between two points on an axis. As shown in Figure 2:
If you want to be arbitrary,
A
、
B
The longitude difference between the two places is that the real number corresponding to the east longitude is a positive real number, and the real number corresponding to the west longitude is a negative real number.
So, for the sake of principle,
A
、
B
The time difference between the two places is:
24
360
|
|
24
360
B
A
x
x
ab blood type
example
1
.
(
2004
National college entrance examination questions)
2002
year
1 1
moon
20
sun
nine
Time (Beijing time)
, China first.
19
Sub-Antarctic
The scientific investigation team set out from Shanghai by the "Snow Dragon"
When the Great Wall Station is located, the area is
(
)
A. 19
sun
19
time
B.20
sun
five
time
C. 19
sun
2 1
time
D.20
sun
2 1
time
Analysis: Because the picture shows the southern hemisphere, the Great Wall stands in
west longitude
six
, the position is set to a point.
A
, and then click
A
The corresponding real number on the number axis is-
60
In the center of Beijing time zone.
The longitude is east longitude.
12
, the position is set to a point.
B
, and then click
B
The corresponding real number on the number axis is
120
, and
AB=
|
-
60
-
120|= 180
What is the time difference between the two places
12
24
360
180
Hours, that is, the time where the Great Wall Station is located is Beijing time.
2002
year
1 1
moon
20
sun
nine
carry forward
12
Just one hour.
19
sun
2 1
, the answer is
C
example
2
(
2004
National college entrance examination questions)
One day,
A city in China.
four
time
30
At sunrise,
18
time
30
Divide the sunset.
O
-
10
-
20
10
20
10
E
20
E
10
W
20
W
A
B
Figure ii
x
A
x
B
A
B
x
According to this answer, the longitude of this city is
(
)
A
.
E
five
.
123
B
.
E
five
.
1 12
C
.
E
five
.
127
D
.
E
135
Analysis: This question is the inverse operation of the previous example. According to the conditions of the question, the sunshine time of this day is
14
Hours, the front here
The afternoon is Beijing time.
1 1
time
30
Points, the land should be in place.
12
That is to say, by noon.
12
E
local time
1 1
time
30
When the time-sharing location is local.
12
Time. such
five
.
24
360
|
|
B
A
x
x
five
.
seven
|
|
B
A
x
x
, because of this.
The ground arrives at noon earlier than Beijing, so the longitude here is:
120
+
7.5
= 127.5
E
, the answer is
C
It is worth mentioning that the positive infinity and negative infinity on the number axis are in the same position, while the east longitude
180
And western classics
180
It is also in the same place, so the two are unified here.
Third,
Calculation of sun height
The noon sun height is the abbreviation of the sun altitude angle, which indicates the inclination of the noon sun rays to the local horizon. That is to say,
The angle formed by the noon sunlight and the tangent plane of the ball passing through the sun irradiation point. This angle is related to the latitude and local position of the direct point of the sun.
About latitude. What is the relationship between them? The rays of the sun can be considered to be parallel, as shown in the following figures 3 and 4, that is.
three
2
1
//
//
l
l
l
Set the local midday sun irradiation point as point.
A
The direct point of the sun is a point.
D
, straight line
l
A little too much.
A
Tangent value,
So∠
Binary-Analog Conversion
It's the local sun height. ∴∠
BAC=
∠
ABO=90
-∠
AOD
，∠A
mean sea level
for
A
、
B
Parallel line
Degree difference, because latitude is divided according to the north and south of the equatorial plane, just like the local time zone difference, the north latitude corresponds to a positive number, and the south latitude corresponds to a positive number.
Negative number, so as to get the formula for calculating the height of the sun:
H=90
-
|
α
-
β
|
(
H
For the height of the sun at noon,
α
When is it?
The latitude of the earth,
β
Is the latitude of the direct point of the sun, where
α
、
β
Take the positive in the north and the negative in the south)
example
three
In recent years, China's real estate industry has developed rapidly, and more and more residents have moved into new houses, and the living conditions and environment have changed significantly.
Oh, my god Look at the picture and answer the questions with the following formula and related knowledge:
(1) The formula of the sun height at noon somewhere:
H=90
-|A-B|
A
For geographical latitude,
B
Direct sunlight geography
Latitude.
A
、
B
It's summer.
Half a year is positive and half a year in winter is negative.
②
tan35
about
0.7
tan45
= 1，tan60
about
1.732