tmeits.github.com/day_length.html at master · tmeits/tmeits.github.com · GitHub

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<title>Computational Dendrochronology Toolbox (CDTBX)</title>
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<h2>Computational Dendrochronology Toolbox (CDTBX)</h2>
<p>Deriving the formulas to calculate the length of day.
<div class="sagecell-plot" id="sagecell2">
<script type="application/sage">
# coding=utf-8
__author__ = 'vilyin'

def day_length(Day, Latitude=(-(36+51/60.))):
    """
        This calculates the number of hours (hours) and fraction of the day (b) in %daylight.
        http://www.gandraxa.com/length_of_day.xml
    """
    if Day < 0:
        Day=0

    Pi=n(pi)
    Axis=23.439*Pi/180.
    j=Pi/182.625 #constant (radians)

    m=1-tan(Latitude*Pi/180.)*tan(Axis*cos(j*Day))
    b=arccos(1-m)/Pi #fraction of the day the sun is up

    if b < 0:
        b=0
    if b > 1:
        b=1
    hours=b*24 #hours of sunlight
    return [b, hours]
def daylight_year(Latitude):
    """
        The length of daylight hours in a year
    """
    Days=range(365)
    for idx in range(365):
        Days[idx] = day_length(idx, Latitude)
        Days[idx][0] = idx
    return Days
def plot_daylight_year(Latitude, LatStr):
    dy=daylight_year(Latitude)
    plt=list_plot(dy, color='steelblue',legend_label=LatStr)
    plt.ymax(25.0); plt.ymin(-1.0)
    plt.xmax(400.0); plt.xmin(0.0)
    plt.axes_labels(['Day', 'Hours'])
    plt.show(aspect_ratio=10,frame=True, gridlines=["major", True])

@interact
def plotDaylight(
    clr=Color('green'),
    manual=checkbox(True, 'Manual'),
    redraw=checkbox(False, 'Redraw'),
    Degrees=slider(0,90, 1, default=66, label='Degrees'),
    Minutes=slider(0,60, 1, default=33,label='Minutes'),
    #plotpoints=('Value of Latitude',[100,500,1000]),
    Sity=('Value of Latitude',['Chokurdakh','Yakutsk','Arizona'])):
    """
        http://www.gandraxa.com/length_of_day.xml
    """

    Latitude=N(Degrees+Minutes/60)
    if Sity == 'Chokurdakh' and manual == False:
        Latitude=N(70.62); LatStr='Chokurdakh=70.62' #https://www.wolframalpha.com/input/?i=Chokurdakh
    elif Sity == 'Yakutsk' and manual == False:
        Latitude=N(62.03); LatStr='Yakutsk=62.03'
    elif Sity == 'Arizona' and manual == False:
        Latitude=N(70.62); LatStr='Arizona'
    elif Latitude == 0:
        LatStr='Equator'
    elif Latitude == 90:
        LatStr='Northpole'
    else:
        LatStr='Latitude=' + ("%2.2f" % N(Degrees+Minutes/60.)).rjust(6)
    if redraw == True:
        dy=daylight_year(N(Latitude))

        plt=list_plot(dy, color='steelblue',legend_label=LatStr)
        plt.ymax(25.0); plt.ymin(-1.0)
        plt.xmax(370.0); plt.xmin(0.0)
        plt.axes_labels(['Day of Year', 'Hours'])
        plt.show(aspect_ratio=10,frame=True, gridlines=["major", True])
    else:
        print daylight_year(N(Latitude))
        var('m')
        show(arccos(1-m)/pi)

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