Calculate radiation

radiation.frm

'++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
' Program untuk menghitung Radiasi
'++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++

Private Sub cmdCal_Click()

Dim LAT As Double
Dim lon As Double
Dim MONTH As Double
Dim hari As Integer

'+++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
'Calculate Julian Date
'+++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
Dim bulan(20), bfeb As Integer
    bulan(1) = 31
    
'Bulan kabisat
If Val(frmRad.cboTahun.Text) Mod 4 = 0 Then bfeb = 29 Else bfeb = 28

    bulan(2) = bulan(1): bulan(3) = bulan(2) + bfeb: bulan(4) = bulan(3) + 31
    bulan(5) = bulan(4) + 30: bulan(6) = bulan(5) + 31: bulan(7) = bulan(6) + 30
    bulan(8) = bulan(7) + 31: bulan(9) = bulan(8) + 31: bulan(10) = bulan(9) + 30
    bulan(11) = bulan(10) + 31: bulan(12) = bulan(11) + 30

'Isi Combo box
    With cboBulan
        If .Text = "January" Then MONTH = 0
        If .Text = "February" Then MONTH = 1
        If .Text = "March" Then MONTH = 2
        If .Text = "April" Then MONTH = 3
        If .Text = "May" Then MONTH = 4
        If .Text = "June" Then MONTH = 5
        If .Text = "July" Then MONTH = 6
        If .Text = "August" Then MONTH = 7
        If .Text = "September" Then MONTH = 8
        If .Text = "October" Then MONTH = 9
        If .Text = "November" Then MONTH = 10
        If .Text = "December" Then MONTH = 11
    End With
    
    If MONTH = 0 Then JulianDate = Val(frmRad.cboTanggal.Text) Else JulianDate = bulan(MONTH) + Val(frmRad.cboTanggal.Text)
'+++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++

Const pi = 3.1415926, gamma = 66.1, lhv = 2.454, dair = 1.204, cp = 1010
Const p0 = 1.000412351, p1 = -1.073807306, wind = 9

hari = JulianDate
plank = 6.626 * (10 ^ -34)
chy = 3 * (10 ^ 8)
bolztman = 5.67 * (10 ^ -8)
lon = Val(txtLon.Text)
LAT = Val(txtLat.Text)
altitude = Val(txtAlt.Text)

'Deklarasi parameter
    If LAT < 0 Then lag = 102 Else lag = 285
    tlag = Abs(LAT) / 2
    Tm1 = 10 - 0.45 * Abs(LAT)
    Td = Tm1 * (0.015 * Abs(LAT) - 0.1)
    b1 = 1.47 - 0.00518 * LAT - 0.00412 * lon - 0.000483 * altitude
    a1 = 19.1 - 18.3 * b1
    a2 = 0.36
    b2 = -0.91 - 0.00111 * LAT + 0.0111 * lon
    a3 = -0.321 - 0.00488 * LAT + 0.00763 * lon
    b3 = 0.0143 - 0.0493 * a3
    b4 = 20.4 + 0.074 * LAT - 0.204 * lon
    a4 = 0.0235 - 0.515 * b4
    b5 = 0.2
    a5 = -3.5

'Panjang Hari
    dekl = -23.4 * Cos(2 * pi * (hari + 10) / 365)
    sinld = Sin(LAT * pi / 180) * Sin(dekl * pi / 180)
    cosld = Cos(LAT * pi / 180) * Cos(dekl * pi / 180)
    sinb = Sin(-0.833 * pi / 180)
    arg = (sinb - sinld) / cosld
    arccos = 2 * Atn(1) - Atn(arg / Sqr(1 - arg * arg))

    dlen = 24 / pi * arccos
    sangot = 1440 / pi * 2 * (arccos * sinld + cosld * Sin(arccos)) * 0.042

'Lama Penyinaran
    nN = Rnd 'a3 + b3
    If nN < 0.05 Then nN = 0.05
    sunshine = nN * dlen

'Solar radiation :
    solar = (a2 + b2 * sunshine / dlen) * sangot
    
    txtRad.Text = solar

End Sub

Private Sub cmdClear_Click()
Unload Me
frmRad.Show
End Sub

Private Sub Form_Load()
'Posisi form ketika pertama kali muncul
    Me.Height = 5145
    Me.Width = 5385
    cboTanggal.Clear: cboBulan.Clear: cboTahun.Clear
    
'Format isian tanggal
For i = 1 To 31
    cboTanggal.AddItem (i)
    cboTanggal.Text = cboTanggal.List(0)
Next i

'Format isian bulan
With cboBulan
    .AddItem ("January")
    .AddItem ("February")
    .AddItem ("March")
    .AddItem ("April")
    .AddItem ("May")
    .AddItem ("June")
    .AddItem ("July")
    .AddItem ("August")
    .AddItem ("September")
    .AddItem ("October")
    .AddItem ("November")
    .AddItem ("December")
    .Text = .List(5)
End With
    
'Format isian tahun
For j = 1998 To 2050
    cboTahun.AddItem (j)
    cboTahun.Text = cboTahun.List(7)
Next j

End Sub