在Google地图上绘制白天和黑夜

12

我想在任意时间点在Google地图上绘制白天/黑夜。我熟悉生成地图图块；我只是在寻找一种算法来告诉我地球上的某个特定点当前处于白天还是黑夜，或者以其他方式将日/夜界面的曲线绘制到地图上。

我已经进行了一些搜索，但是可能我对这里的问题域甚至还不了解，无法知道要搜索的术语！

有任何想法吗？不一定是完美的-基本上，我正在将日出和日落照片的Flickr地理位置数据（及其“拍摄日期”时间戳）与现实进行比较，这是为了帮助我对其进行可视化。

google-maps algorithm

— 马特·吉布森
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解决方案也出现在gis.stackexchange.com/questions/17184/…一个非常相关的问题中。

— ub

6

此页面给出的方程式的精确度为1度。看起来这段代码也可以计算出来，但我实际上没有检查。

— 伊恩·特顿
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太棒了，正是我想要的东西。是的，看起来像vplanet.c中的projillum（）函数在该代码中与该算法非常匹配，因此，绝对可以让我朝正确的方向前进，谢谢。

— 马特·吉布森

2

也是一个示例 http://blog.char95.com/demos/daylight-on-google-maps/

    Sunrise/Sunset Algorithm

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
        NOTE: the algorithm assumes the use of a calculator with the
        trig functions in "degree" (rather than "radian") mode. Most
        programming languages assume radian arguments, requiring back
        and forth convertions. The factor is 180/pi. So, for instance,
        the equation RA = atan(0.91764 * tan(L)) would be coded as RA
        = (180/pi)*atan(0.91764 * tan((pi/180)*L)) to give a degree
        answer with a degree input for L.


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

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)

3. calculate the Sun's mean anomaly

    M = (0.9856 * t) - 3.289

4. calculate the Sun's true longitude

    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

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

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)

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

    RA = RA / 15

6. calculate the Sun's declination

    sinDec = 0.39782 * sin(L)
    cosDec = cos(asin(sinDec))

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)

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

8. calculate local mean time of rising/setting

    T = H + RA - (0.06571 * t) - 6.622

9. adjust back to UTC

    UT = T - lngHour
    NOTE: UT potentially needs to be adjusted into the range [0,24) by adding/subtracting 24

10. convert UT value to local time zone of latitude/longitude

    localT = UT + localOffset

使用算法 http://williams.best.vwh.net/sunrise_sunset_algorithm.htm

— Mapperz
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