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Mr.Right

不顾一切的去想,于是我们有了梦想。脚踏实地的去做,于是梦想成了现实。

 
 
 

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人生一年又一年,只要每年都有所积累,有所成长,都有那么一次自己认为满意的花开时刻就好。即使一时不顺,也要敞开胸怀。生命的荣枯并不是简单的重复,一时的得失不是成败的尺度。花开不是荣耀,而是一个美丽的结束,花谢也不是耻辱,而是一个低调的开始。

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把太阳当成卫星计算日出日落时间  

2012-11-01 18:12:58|  分类: 学习 |  标签: |举报 |字号 订阅

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Sunrise/Sunset Algorithm Example
Source:
Almanac for Computers, 1990
published by Nautical Almanac Office
United States Naval Observatory
Washington, DC 20392

Inputs:
day, month, year:      date of sunrise/sunset
latitude, longitude:   location for sunrise/sunset
zenith:                Sun's zenith for sunrise/sunset
 offical      = 90 degrees 50'
 civil        = 96 degrees
 nautical     = 102 degrees
 astronomical = 108 degrees
NOTE: longitude is positive for East and negative for West

Worked example (from book):
June 25, 1990: 25, 6, 1990
Wayne, NJ:      40.9, -74.3
Office zenith:  90 50' cos(zenith) = -0.01454


1. first calculate the day of the year

N1 = floor(275 * month / 9)
N2 = floor((month + 9) / 12)
N3 = (1 + floor((year - 4 * floor(year / 4) + 2) / 3))
N = N1 - (N2 * N3) + day - 30
Example:
N1 = 183
N2 = 1
N3 = 1 + floor((1990 - 4 * 497 + 2) / 3)
  = 1 + floor((1990 - 1988 + 2) / 3)
  = 1 + floor((1990 - 1988 + 2) / 3)
  = 1 + floor(4 / 3)
  = 2
N = 183 - 2 + 25 - 30 = 176

2. convert the longitude to hour value and calculate an approximate time

lngHour = longitude / 15
if rising time is desired:
 t = N + ((6 - lngHour) / 24)
if setting time is desired:
 t = N + ((18 - lngHour) / 24)
Example:
lngHour = -74.3 / 15 = -4.953
t = 176 + ((6 - -4.953) / 24)
 = 176.456
3. calculate the Sun's mean anomaly
M = (0.9856 * t) - 3.289
Example:
M = (0.9856 * 176.456) - 3.289
 = 170.626

4. calculate the Sun's true longitude
       [Note throughout the arguments of the trig functions
       (sin, tan) are in degrees. It will likely be necessary to
       convert to radians. eg sin(170.626 deg) =sin(170.626*pi/180
       radians)=0.16287]
L = M + (1.916 * sin(M)) + (0.020 * sin(2 * M)) + 282.634
NOTE: L potentially needs to be adjusted into the range [0,360) by adding/subtracting 360
Example:
L = 170.626 + (1.916 * sin(170.626)) + (0.020 * sin(2 * 170.626)) + 282.634
 = 170.626 + (1.916 * 0.16287) + (0.020 * -0.32141) + 282.634
 = 170.626 + 0.31206 + -0.0064282 + 282.634
 = 453.566 - 360
 = 93.566

5a. calculate the Sun's right ascension
RA = atan(0.91764 * tan(L))
NOTE: RA potentially needs to be adjusted into the range [0,360) by adding/subtracting 360
Example:
RA = atan(0.91764 * -16.046)
  = atan(0.91764 * -16.046)
  = atan(-14.722)
  = -86.11412

5b. right ascension value needs to be in the same quadrant as L

Lquadrant  = (floor( L/90)) * 90
RAquadrant = (floor(RA/90)) * 90
RA = RA + (Lquadrant - RAquadrant)
Example:
Lquadrant  = (floor(93.566/90)) * 90
          = 90
RAquadrant = (floor(-86.11412/90)) * 90
          = -90
RA = -86.11412 + (90 - -90)
  = -86.11412 + 180
  = 93.886

5c. right ascension value needs to be converted into hours

RA = RA / 15
Example:
RA = 93.886 / 15
  = 6.259

6. calculate the Sun's declination

sinDec = 0.39782 * sin(L)
cosDec = cos(asin(sinDec))
Example:
sinDec = 0.39782 * sin(93.566)
      = 0.39782 * 0.99806
      = 0.39705
cosDec = cos(asin(0.39705))
      = cos(asin(0.39705))
      = cos(23.394)
      = 0.91780

7a. calculate the Sun's local hour angle
cosH = (cos(zenith) - (sinDec * sin(latitude))) / (cosDec * cos(latitude))
if (cosH >  1) 
 the sun never rises on this location (on the specified date)
if (cosH < -1)
 the sun never sets on this location (on the specified date)
Example:
cosH = (-0.01454 - (0.39705 * sin(40.9))) / (0.91780 * cos(40.9))
    = (-0.01454 - (0.39705 * 0.65474)) / (0.91780 * 0.75585)
    = (-0.01454 - 0.25996) / 0.69372
    = -0.2745 / 0.69372
    = -0.39570

7b. finish calculating H and convert into hours
if if rising time is desired:
 H = 360 - acos(cosH)
if setting time is desired:
 H = acos(cosH)
H = H / 15
Example:
H = 360 - acos(-0.39570)
 = 360 - 113.310   [ note result of acos converted to degrees]
 = 246.690
H = 246.690 / 15
 = 16.446

8. calculate local mean time of rising/setting
T = H + RA - (0.06571 * t) - 6.622
Example:
T = 16.446 + 6.259 - (0.06571 * 176.456) - 6.622
 = 16.446 + 6.259 - 11.595 - 6.622
 = 4.488

9. adjust back to UTC
UT = T - lngHour
NOTE: UT potentially needs to be adjusted into the range [0,24) by adding/subtracting 24
Example:
UT = 4.488 - -4.953
  = 9.441
  = 9h 26m

10. convert UT value to local time zone of latitude/longitude
localT = UT + localOffset
Example:
localT = 9h 26m + -4
      = 5h 26m
      = 5:26 am EDT

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