Dim CosZenith, pi
Dim Field(7)
CosZenith=-0.014543897651582	' cos(sun's civil zenith) = cos(90deg 50mins)
pi= 4 * Atn(1)
Sub Submit1_onclick ()
Dim StartText, FinishText		' strings from webpage form
Dim GCLatitude, GCLongitude		' lat & lon in rads for waypoints on GC track
Dim GCLatitudeOld, GCLongitudeOld
Dim UTSR, UTSS 					' UTC times for sunrise & sunset
Dim Latitude1, Longitude1		' lat/lon for the dep point expressed as radians
Dim Latitude2, Longitude2 		' lat/lon for the arr point expressed as radians
Dim DistanceRad					' =distance in radians between start & finish
Dim DistanceNM					' GC distance in nautical miles
Dim DistAlongGCRad				' distance along GC track in radians
Dim Increment, LoopCounter
Dim Counter, Counter1			' the time interval in decimal hours between waypoints
Dim InitialTrueCourseRad		' Initial True Course along GC track in rads
Dim DecDepTime, DecArrTime 		' departure & arrival times in decimal
Dim DepDate, ArrDate			' departure & arrival dates in VB date format
Dim Groundspeed, FltTime 		' average Groundspeed & Flight Time
Dim LoopTime					' time now during loop
Dim CumFltTimeDay, CumFltTimeNight	' cumalative day & night totals of time
Dim	DLongitude
Dim DateStart					' start date of departure
Dim BreakOut					' Logic Variable
Dim TextAreaStr(10)				' holds string data for results
Dim TextStr(6)					' holds strings
Dim GCTrackData()				' Array for GC waypoint data
Dim Temp
' format of long/lat positions is 15 digit string
' pos 1 - "N" or "S" - north or south indicator
' pos 2 to 3 - whole degrees of latitude
' pos 4 to 7 - minutes of latitude accurate to 1 decimal place
' pos 8 - "E" or "W" - east or west indicator
' pos 9 to 11 - whole degrees of longitude
' pso 12 to 15 - minutes of longitude accurate to 1 decimal place
' lat N=+ve, S=-ve
' lon E=+ve, W=-ve
' Initilize Field() variable
For Counter= 1 To 7
	Field(Counter)=0
Next
' Start of Dep & Arr points CX
StartText=uCase(trim(text1.value))
FinishText=uCase(trim(text2.value))
If StartText=FinishText Then
	MsgBox("Error: Departure and Arrival points are the same.")
End If
Select Case CheckLatLon(StartText)
	Case -1
		MsgBox("Error in departure point lat/lon")
		Exit Sub
	Case -2
		field(1)=-1
End Select
Select Case CheckLatLon(FinishText)
	Case -1
		MsgBox("Error in arrival point lat/lon")
		Exit Sub
	Case -2
		field(2)=-1
End Select
If Field(1)<>-1 Then
	Latitude1=((Eval(Mid(StartText,2,2))+(Eval(Mid(StartText,4,4))/60))*pi)/180
	Longitude1=((Eval(Mid(StartText,9,3))+(Eval(Mid(StartText,12,4))/60))*pi)/180
		If Mid(StartText,1,1)="S" Then Latitude1=Latitude1*-1
		If Mid(StartText,8,1)="W" Then Longitude1=Longitude1*-1
End If
If Field(2)<>-1 Then
	Latitude2=((Eval(Mid(FinishText,2,2))+(Eval(Mid(FinishText,4,4))/60))*pi)/180
	Longitude2=((Eval(Mid(FinishText,9,3))+(Eval(Mid(FinishText,12,4))/60))*pi)/180
		If Mid(FinishText,1,1)="S" Then Latitude2=Latitude2*-1
		If Mid(FinishText,8,1)="W" Then Longitude2=Longitude2*-1
End If
' End of Dep & Arr point CX
' Start Of Times CX
Select Case CheckTime(text5.value)
	Case -1
		MsgBox("Error in Departure Time")
		Exit Sub
	Case -2
		Field(5)=-1
End Select
Select Case CheckTime(text6.value)
	Case -1
		MsgBox("Error in Arrival Time")
		Exit Sub
	Case -2
		Field(6)=-1
End Select
If Field(5)<>-1 Then DecDepTime=TimeStringToDecimal(text5.value)
If Field(6)<>-1 Then DecArrTime=TimeStringToDecimal(text6.value)
' End of Times CX
' Start of date CX
Select Case CheckDate(text3.value)
	Case -1
	MsgBox("Error in Departure Date")
	Exit Sub
	Case -2
	Field(3)=-1
End Select
Select Case CheckDate(text4.value)
	Case -1
	MsgBox("Error in Arrival Date")
	Exit Sub
	Case -2
	Field(4)=-1
End Select
If Field(3)<>-1 Then DepDate=CDate(text3.value)
If Field(4)<>-1 Then ArrDate=CDate(text4.value)
If Field(3)<>-1 Then
	DepDate=CDate(text3.value)
	DateStart=DepDate	' inital value set to departure date
End If
If Field(1)=-1 And Field(2)=-1 Then
	MsgBox("Please enter Depart Point and/or Arrival Point")
	Exit Sub
End If
If Field(3)<>-1 And Field(4)<>-1 And Field(5)<>-1 And Field(6)<>-1 Then
	If DecArrTime<=DecDepTime And ArrDate=DepDate Then
		MsgBox("Error: Arrival Time is same as/prior to Departure Time")
		Exit Sub
	End If
End If
' the great circle distance in nm between two points
' Only executed if departure and arrival points entered on webpage
If Field(1)<>-1 And field(2)<>-1 Then
	DistanceRad=Acos(Sin(Latitude1)*Sin(Latitude2)+Cos(Latitude1)*Cos(Latitude2)*Cos(Longitude1*-1-Longitude2*-1))
	DistanceNM=DistanceRad*180*60/pi ' distance converted to nautical miles
	InitialTrueCourseRad=TrueCourseRad(Latitude1, Longitude1, Latitude2, Longitude2)
End If
' If departure point was a pole then code effectively breaks to here
' calculate the flight time. Note may be more than 24hrs
' If departure and arrival the same day easy
If Field(3)<>-1 And Field(4)<>-1 And Field(5)<>-1 And Field(6)<>-1 Then
	If ArrDate=DepDate Then
		FltTime=DecArrTime-DecDepTime
	Else
		FltTime=(((ArrDate-DepDate)-1)*24)+(24-DecDepTime)+DecArrTime ' If dIfferent days then not so easy
	End If
	Groundspeed=DistanceNM/FltTime	' calc average Groundspeed
End If
LoopTime=DecDepTime	' start at dep time
LoopCounter=0		' initialise Counter
If Field(1)<>-1 And Field(2)<>-1 And Field(3)<>-1 And Field(4)<>-1 And Field(5)<>-1 And Field(6)<>-1 Then
	If Eval(text7.value)>59 Then
		MsgBox("Max Value of Time Interval is 59 mins")
	Exit Sub
	ElseIf eval(text7.value)<0 Then
		MsgBox("Min Value of Time Interval is 1 Min")
	Exit Sub
	ElseIf eval(text7.value)=False then
		MsgBox("Error in Time Interval Value. Please re-enter")
	Exit Sub
	End If
	ReDim GCTrackData(Fix(FltTime+2)*(60/Eval(text7.value)),6) ' Dimension array
	Increment=Eval(text7.value)/60	' decimal time increment
	' start loop that calculates day/night time
	DO
		If LoopCounter>0 Then
			GCLatitudeOld=GCLatitude
			GCLongitudeOld=GCLongitude
		End If
		DistAlongGCRad=(Groundspeed*Increment*LoopCounter)*pi/(180*60)				' calculate distance along track
		GCLatitude=Asin(Sin(Latitude1)*Cos(DistAlongGCRad)+Cos(Latitude1)*Sin(DistAlongGCRad)*Cos(InitialTrueCourseRad))			' calc new latitude of waypoint
		DLongitude=Atan2(Sin(InitialTrueCourseRad)*Sin(DistAlongGCRad)*Cos(Latitude1), Cos(DistAlongGCRad)-Sin(Latitude1)*Sin(GCLatitude) )	' calc dIfference in longtude
		GCLongitude=Modulus((Longitude1*-1)-DLongitude+pi, 2*pi)-pi						' calc new longitude of waypoint
		GCLongitude=GCLongitude*-1											' ensure correct sign for E or W
		UTSR=CalcSRSSTimes(DateStart, Deg(GCLatitude), Deg(GCLongitude),0)	' calc time of sunrise at the waypoint
		UTSS=CalcSRSSTimes(DateStart, Deg(GCLatitude), Deg(GCLongitude),1)	' calc time of sunset at waypoint
		' user has selected aviation time so Subtract 1/2 hour
		If checkbox1.status=False Then
			UTSR=UTSR-0.5
		End If
		' factor time in case not in range 0<=UTSR<=23:59
		If UTSR>24 And UTSR<98 Then
			UTSR=UTSR-24
		ElseIf UTSR<0 And UTSR>-98 Then
			UTSR=UTSR+24
		End If
		If checkbox1.status=False Then
			UTSS=UTSS+0.5	' user has Selected aviation time so add 1/2 hour
		End If
		' factor time in Case not in range 0<=UTSR<=23:59
		If UTSS>24 And UTSS<98 Then
			UTSS=UTSS-24
		ElseIf UTSS<0 And UTSS >-98 Then
			UTSS=UTSS+24
		End If
		' If the final waypoint's time is less than Increment from arrival
		' Then reduce Increment to equal time left until arrival time.
		' eg arrival time=12:00, time (LoopTime) at last waypoint is 11:58
		' Then final Increment = 2 minutes (2/60). Ensures that the
		' total of day and night times equals the flight time.
		If DateStart=ArrDate And (DecArrTime-LoopTime)<Increment Then
			Increment=DecArrTime-LoopTime
		End If
		' If DateStart=ArrDate-1 Then
			' If 24.0-LoopTime<Increment Then
				' Increment=24.0-LoopTime
			' End If
		' End If
		BreakOut=0
		If UTSR=99 Then
			CumFltTimeNight=CumFltTimeNight+Increment
			BreakOut=1
		ElseIf UTSR=-99 Then
			CumFltTimeDay=CumFltTimeDay+Increment
			BreakOut=1
		End If
		If BreakOut<>1 Then
			If UTSS=99 Then
				CumFltTimeNight=CumFltTimeNight+Increment
				BreakOut=1
			ElseIf UTSS=-99 Then
				CumFltTimeDay=CumFltTimeDay+Increment
				BreakOut=1
			End If
		End If
		If BreakOut<>1 Then
			If UTSR<UTSS Then
				If LoopTime>=UTSR And LoopTime<UTSS Then
					CumFltTimeDay=CumFltTimeDay+Increment
				Else
					CumFltTimeNight=CumFltTimeNight+Increment
					BreakOut=1
				End If
			End If
		End If
		If BreaOut<>1 Then
			If UTSR>UTSS Then
				If LoopTime>=UTSR OR LoopTime<UTSS Then
					CumFltTimeDay=CumFltTimeDay+Increment
				Else
					CumFltTimeNight=CumFltTimeNight+Increment
					BreakOut=1
				End If
			End If
		End If
		If checkbox2.status=True Then
			If Len(cstr(LoopCounter))=4 Then
				GCTrackData(LoopCounter,1)="0"+cstr(LoopCounter)
			ElseIf Len(cstr(LoopCounter))=3 Then
				GCTrackData(LoopCounter,1)="00"+cstr(LoopCounter)
			ElseIf Len(cstr(LoopCounter))=2 Then
				GCTrackData(LoopCounter,1)="000"+cstr(LoopCounter)
			ElseIf Len(cstr(LoopCounter))=1 Then
				GCTrackData(LoopCounter,1)="0000"+cstr(LoopCounter)
			Else
				GCTrackData(LoopCounter,1)=cstr(LoopCounter)
			End If
			GCTrackData(LoopCounter,2)=cstr(DateStart)
			GCTrackData(LoopCounter,3)=DecHourToString(LoopTime)
			GCTrackData(LoopCounter,4)=LatitudeDegreesToString(Deg(GCLatitude))
			GCTrackData(LoopCounter,5)=LongitudeDegreesToString(Deg(GCLongitude))
			If LoopCounter>0 Then
				GCTrackData(LoopCounter-1,6)=Cstr(Round(Deg(TrueCourseRad(GCLatitudeOld, GCLongitudeOld, GCLatitude, GCLongitude)),1))
			End If
		End If
		LoopCounter=LoopCounter+1	' increase LoopCounter by 1
		LoopTime=LoopTime+Increment	' increase time now by Increment
		' If LoopTime goes over 24:00 Then must be a new day
		If LoopTime>=24.0 Then
			DateStart=DateStart+1	' add a day to date&
			LoopTime=LoopTime-24	' Subtract 24:00 to get correct am time on new day
		End If
	Loop UNTIL ( (LoopTime>=DecArrTime) And (DateStart=ArrDate) )
	' keep looping until we get to the correct day and time
	' If checkbox2.status=True Then GCTrackData(LoopCounter-1,6)=Cstr(Round(Deg(TrueCourseRad(GCLatitude, GCLongitude, Latitude2, Longitude2)),1))
	' MsgBox("looptime="+cstr(loopcounter))
	If checkbox2.status=True Then
		If Len(cstr(LoopCounter))=4 Then
			GCTrackData(LoopCounter,1)="0"+cstr(LoopCounter)
		ElseIf Len(cstr(LoopCounter))=3 Then
			GCTrackData(LoopCounter,1)="00"+cstr(LoopCounter)
		ElseIf Len(cstr(LoopCounter))=2 Then
			GCTrackData(LoopCounter,1)="000"+cstr(LoopCounter)
		ElseIf Len(cstr(LoopCounter))=1 Then
			GCTrackData(LoopCounter,1)="0000"+cstr(LoopCounter)
		Else
			GCTrackData(LoopCounter,1)=Cstr(LoopCounter)
		End If
		GCTrackData(LoopCounter,2)=Cstr(DateStart)
		GCTrackData(LoopCounter,3)=DecHourToString(DecArrTime)
		GCTrackData(LoopCounter,4)=LatitudeDegreesToString(Deg(Latitude2))
		GCTrackData(LoopCounter,5)=LongitudeDegreesToString(Deg(Longitude2))
		GCTrackData(LoopCounter-1,6)=Cstr(Round(Deg(TrueCourseRad(GCLatitude, GCLongitude, Latitude2, Longitude2)),1))
		If GCTrackData(LoopCounter,3)=GCTrackData(LoopCounter-1,3) Then
			GCTrackData(LoopCounter-1,6)=""
			For Counter=1 To 6
				GCTrackData(LoopCounter,Counter)=""
			Next
		End If
	End If
End If
If DistanceNM>0 Then
	TextAreaStr(2)="Great Circle Distance = "+CStr(Round(DistanceNM,2))+"nm "+CStr(Round((DistanceNM*1.150779),2))+"mls "+CStr(Round((DistanceNM*1.852),2))+"kms"
End If
If CumFltTimeNight+CumFltTimeDay>0 Then
	TextAreaStr(1)="Total Flt Time = "+DecHourToString(CumFltTimeNight+CumFltTimeDay)+" Total Day = "+DecHourToString(CumFltTimeDay)+" Total Night = "+DecHourToString(CumFltTimeNight)
	TextAreaStr(3)="Average Grounspeed = "+CStr(Round(Groundspeed,2))+"nm/h "+CStr(Round((Groundspeed*1.150779),2))+"mph "+CStr(Round((Groundspeed*1.852),2))+"km/h"
End If
If Field(1)<>-1 And Field(2)<>-1 Then
	TextAreaStr(4)="Initial True Course is "+CStr(Round(Deg(InitialTrueCourseRad),1))+" degrees(T)"
Else
	TextAreaStr(4)="No second waypoint - course undefined"
End If
TextStr(1)="Sunrise "
TextStr(2)="Sunset "
TextStr(3)="Departure point-"
TextStr(4)="Arrival point-"
TextStr(5)="Sun never rises"
TextStr(6)="Sun never sets"
If Field(1)<>-1 And Field(3)<>-1 Then
	Select Case CalcSRSSTimes(DepDate,Deg(Latitude1),Deg(Longitude1),0)
		Case 99	TextAreaStr(5)=TextStr(3)+TextStr(1)+TextStr(5)
		Case -99 TextAreaStr(5)=TextStr(3)+TextStr(1)+TextStr(6)
		Case Else TextAreaStr(5)=TextStr(3)+TextStr(1)+DecHourToString(CalcSRSSTimes(DepDate,Deg(Latitude1),Deg(Longitude1),0))+"z"
	End Select
	Select Case CalcSRSSTimes(DepDate,Deg(Latitude1),Deg(Longitude1),1)
		Case 99	TextAreaStr(6)=TextStr(3)+TextStr(2)+TextStr(5)
		Case -99 TextAreaStr(6)=TextStr(3)+TextStr(2)+TextStr(6)
		Case Else TextAreaStr(6)=TextStr(3)+TextStr(2)+DecHourToString(CalcSRSSTimes(DepDate,Deg(Latitude1),Deg(Longitude1),1))+"z"
	End Select
Else
	TextAreaStr(5)=""
	TextAreaStr(6)=""
End If
If Field(2)<>-1 And Field(4)<>-1 Then
	Select Case CalcSRSSTimes(ArrDate,Deg(Latitude2),Deg(Longitude2),0)
		Case 99	TextAreaStr(7)=TextStr(4)+TextStr(1)+TextStr(5)
		Case -99 TextAreaStr(7)=TextStr(4)+TextStr(1)+TextStr(6)
		Case Else TextAreaStr(7)=TextStr(4)+TextStr(1)+DecHourToString(CalcSRSSTimes(ArrDate,Deg(Latitude2),Deg(Longitude2),0))+"z"
	End Select
	Select Case CalcSRSSTimes(ArrDate,Deg(Latitude2),Deg(Longitude2),1)
		Case 99	TextAreaStr(8)=TextStr(4)+TextStr(2)+TextStr(5)
		Case -99 TextAreaStr(8)=TextStr(4)+TextStr(2)+TextStr(6)
		Case Else TextAreaStr(8)=TextStr(4)+TextStr(2)+DecHourToString(CalcSRSSTimes(ArrDate,Deg(Latitude2),Deg(Longitude2),1))+"z"
	End Select
Else
	TextAreaStr(7)=""
	TextAreaStr(8)=""
End If
TextAreaStr(0)="Results for"
textarea1.value=String(79,"*")+vbNewLine+textarea1.value
' Loop to print GC route data
If checkbox2.status=True And Field(1)<>-1 And Field(2)<>-1 And Field(3)<>-1 And Field(4)<>-1 And Field(5)<>-1 And Field(6)<>-1 Then
	Counter=LoopCounter
	Do
		For Counter1 = 6 To 1 step -1
			textarea1.Value=GCTrackData(Counter,Counter1)+"      "+textarea1.Value
		next
		Counter=Counter-1
		textarea1.value=vbNewLine+textarea1.value
	Loop Until Counter=-1
	textarea1.value="Waypoint     Date        Time(UTC)   Latitude     Longitude   True Course"+vbNewLine+textarea1.value
End If
textarea1.value=vbNewLine+textarea1.value
For Counter=1 To 5 Step 2
	TextAreaStr(0)=TextAreaStr(0)+" "+eval("text"+cstr(counter)+".value")
Next
For Counter=2 To 6 Step 2
	TextAreaStr(0)=TextAreaStr(0)+" "+eval("text"+cstr(counter)+".value")
Next
If checkbox2.status=False Then
	TextAreaStr(0)=TextAreaStr(0)+vbNewLine+"No Great Circle route data selected"
Else
	TextAreaStr(0)=TextAreaStr(0)+vbNewLine+"Great Circle route data selected"
End If
If checkbox1.status=False Then
	TextAreaStr(0)=TextAreaStr(0)+"  "+"Aviation Sunset/Sunrise Time Selected"
Else
	TextAreaStr(0)=TextAreaStr(0)+"  "+"Actual Sunset/Sunrise Time Selected"
End If
For Counter = 8 To 0 Step -1
 textarea1.Value=TextAreaStr(Counter)+vbNewLine+textarea1.Value
Next
' Loop Until GCTrackData(Counter,2)=""
End Sub
' *******************Functions Start*******************************
Function TrueCourseRad(LatRad1, LonRad1, LatRad2, LonRad2)
' returns true course in rads between two points
Dim DistanceRads
Dim TrueCourseValRad
If LatRad1=pi/2 Then
	TrueCourseRad=pi
	' If departure point is the North pole Then true course to ANY destination must be 180deg or pi rads
	' Exit as do not need to calculate initial true course
	Exit Function
ElseIf LatRad1=-pi/2 Then
	TrueCourseRad=0
	' If departure point is the Sounth pole Then true course to ANY destination must be 000deg or 0 rads
	Exit Function
End If
DistanceRads=2*asin(sqr((sin((LatRad1-LatRad2)/2))^2 + cos(LatRad1)*cos(LatRad2)*(sin((lonrad1-lonrad2)/2))^2))
TrueCourseValRad=(Sin(LatRad2)-Sin(LatRad1)*Cos(DistanceRads))/(Sin(DistanceRads)*Cos(LatRad1))
' correct for double precision arithmetic errors
If TrueCourseValRad>1 Then
	TrueCourseValRad=1
End If
If TrueCourseValRad<-1 Then
	TrueCourseValRad=-1
End If
' initial true course from dep point to arr point
' note the dep point cannot be one of the poles - the above code takes care of pole departures
If Sin((LonRad2*-1)-(LonRad1*-1))<0 Then
	TrueCourseRad=Acos(TrueCourseValRad)
Else
	TrueCourseRad=2*pi-Acos(TrueCourseValRad)
End If
End Function
Function CheckTime (TimeStr)
' check to see if a string is a valid 24 hr time format hh:mm
If TimeStr="" Then
	CheckTime=-2
	Exit Function
End If
If Len(TimeStr)<5 Then
	CheckTime=-1
	Exit Function
End If
If Mid(TimeStr,3,1)<>":" Then
	CheckTime=-1
	Exit Function
ElseIf Eval(Mid(TimeStr,1,2))>23 Then
	CheckTime=-1
	Exit Function
ElseIf Eval(Mid(TimeStr,4,2))>59 Then
	CheckTime=-1
	Exit Function
End If
CheckTime=0
End Function
Function CheckDate (DateStr)
' checks date strings to see if are valid format dd/mm/yyyy
If DateStr="" Then
	CheckDate=-2
	Exit Function
End If
If Len(DateStr)<10 Then
	CheckDate=-1
	Exit Function
End If
If Mid(DateStr,3,1)<>"/" Then
	CheckDate=-1
	Exit Function
ElseIf Mid(DateStr,6,1)<>"/" Then
	CheckDate=-1
	Exit Function
ElseIf Eval(Mid(DateStr,1,2))>31 Then
	CheckDate=-1
	Exit Function
ElseIf Eval(Mid(DateStr,1,2))=0 Then
	CheckDate=-1
	Exit Function
ElseIf Eval(Mid(DateStr,4,2))>12 Then
	CheckDate=-1
	Exit Function
ElseIf Eval(Mid(DateStr,4,2))=0 Then
	CheckDate=-1
	Exit Function
End If
CheckDate=0
End Function
Function CheckLatLon (CheckStr)
' to check that CheckStr is a valid lat & lon string
If CheckStr="" Then
	CheckLatLon=-2
	Exit Function
End If
If Mid(CheckStr,1,1)<>"N" AND Mid(CheckStr,1,1)<>"S" Then
	CheckLatLon=-1
	Exit Function
ElseIf Mid(CheckStr,8,1)<>"E" AND Mid(CheckStr,8,1)<>"W" Then
	CheckLatLon=-1
	Exit Function
ElseIf len(CheckStr)<>15 Then
	CheckLatLon=-1
	Exit Function
End If
If Eval(Mid(CheckStr,2,6))>9000.0 or Eval(Mid(CheckStr,2,6))<0.0 Then
	CheckLatLon=-1
	Exit Function
ElseIf Eval(Mid(CheckStr,9,7))>18000 or Eval(Mid(CheckStr,9,7))<0 Then
	CheckLatLon=-1
	Exit Function
End If
If Mid(CheckStr,6,1)<>"." or Mid(CheckStr,14,1)<>"." Then
	CheckLatLon=-1
	Exit Function
End If
CheckLatLon=0
End Function
Function CalcSRSSTimes (dte,plat,plon,typ)
' calculates sunrise or sunset times
' dte=VB date variant
' plat=latitude in degrees, plon=longitude in degrees
' If typ=0 returns sunrise times
' If typ=1 returns sunset times
Dim DayNumOfYear			' The number of the day in the year
Dim t, SunTrueLongitude, SunsRightAscention, Lquadrant, RAquadrant
Dim SinSunDeclination, CosSunDeclination, SunLocalHourAngle, SunHour, SunTimeUTC
Dim lat, lon
lat=plat
lon=plon
DayNumOfYear=Int(275*month(dte)/9.0)-( Int((month(dte)+9)/12.0) * (1+Int((year(dte)-4*Int(year(dte)/4.0)+2)/3.0)))+day(dte)-30
If typ=0 Then t=DayNumOfYear+((6-(lon/15.0))/24.0)
If typ=1 Then t=DayNumOfYear+((18-(lon/15.0))/24.0)
SunTrueLongitude=((0.9856*t)-3.289)+(1.916*Sin(Rad(((0.9856*t)-3.289))))+(0.020*Sin(Rad(2*((0.9856*t)-3.289))))+282.634
If SunTrueLongitude>360 Then SunTrueLongitude=SunTrueLongitude-360
If SunTrueLongitude<0 Then SunTrueLongitude=SunTrueLongitude+360
SunsRightAscention=Deg(ATN(0.91764*Tan(Rad(SunTrueLongitude))))
Lquadrant=(Int((SunTrueLongitude/90.0)))*90.0
RAquadrant=(Int((SunsRightAscention/90.0)))*90.0
SunsRightAscention=(SunsRightAscention+(Lquadrant-RAquadrant))/15
SinSunDeclination=0.39782*Sin(Rad(SunTrueLongitude))
CosSunDeclination=Cos(Asin(SinSunDeclination))
If plat=90 Then lat=89.999999999
If plat=-90 Then lat=-89.9999999999
SunLocalHourAngle=(CosZenith-(SinSunDeclination*Sin(Rad(LAT)))) / (CosSunDeclination*Cos(Rad(lat)))
If SunLocalHourAngle>1 Then
	SunTimeUTC=99 ' Sun nver rises
	CalcSRSSTimes=SunTimeUTC
	Exit Function
End If
If SunLocalHourAngle<-1 Then
	SunTimeUTC=-99 ' sun never sets
	CalcSRSSTimes=SunTimeUTC
	Exit Function
End If
If typ=0 Then SunHour=(360-Deg(Acos(SunLocalHourAngle)))/15
If typ=1 Then SunHour=(Deg(Acos(SunLocalHourAngle)))/15
SunTimeUTC=(SunHour+SunsRightAscention-(0.06571*t)-6.622)-lon/15.0
If SunTimeUTC<0 Then SunTimeUTC=SunTimeUTC+24
If SunTimeUTC>24 Then SunTimeUTC=SunTimeUTC-24
CalcSRSSTimes=SunTimeUTC
End Function
Function Deg (n) ' converts radians to degrees
Deg=n*180/pi
End Function
Function Rad (n) ' converts degress to radians
Rad=(pi*n)/180
End Function
Function Acos (x) ' ArcCosine(x)
If x=-1 Then
	Acos=pi
ElseIf x=1 Then
	Acos=0
Else
	Acos = Atn(-x / Sqr(-x * x + 1)) + 2 * Atn(1)
End If
End Function
Function Asin (x) 'Arc Sine(x)
If x=-1 Then
	Asin=-pi/2
ElseIf x=1 Then
	Asin=pi/2
Else
	Asin=Atn(X / Sqr(-X * X + 1))
End If
End Function
Function TimeStringToDecimal(TimeString)
' converts time string(hh:mm) to decimal
TimeStringToDecimal=Eval(Mid(Timestring,1,2))+Eval(Mid(TimeString,4,2))/60
End Function
Function LongitudeDegreesToString (DegLongitudeValue)
' converts a decimal degree value to a latitude string
Dim x, y, z, DegreeStr, MinuteStr, DecimalStr
x=Abs(Fix(DegLongitudeValue))
If Abs(DegLongitudeValue)>180 Then
	LongitudeDegreesToString="Error Longitude >180"
	Exit Function
End If
If Abs(DegLongitudeValue)<1 Then
	y=Round(Abs(DegLongitudeValue*60),1)
Else
	y=round((Abs(DegLongitudeValue)-x)*60,1)
End If
If y<10 Then
	MinuteStr="0"+Cstr(Fix(y))
Else
	MinuteStr=Cstr(Fix(y))
End If
z=Abs(y)-Fix(ABS(y))
If z=0 Then
	DecimalStr="0"
Else
	DecimalStr=Mid(Cstr(round(z,1)),3,1)
End If
If MinuteStr="60" Then
	MinuteStr="00"
	x=x+1
End If
If x<10 and x>=1 Then
	DegreeStr="00"+Cstr(x)
ElseIf x<1 Then
	DegreeStr="000"
ElseIf x>=10 and x<100 Then
	DegreeStr="0"+Cstr(x)
Else
	DegreeStr=Cstr(x)
End If
If DegLongitudeValue>0 Then
	LongitudeDegreesToString="E"+DegreeStr+MinuteStr+"."+DecimalStr
Else
	LongitudeDegreesToString="W"+DegreeStr+MinuteStr+"."+DecimalStr
End If
End Function
Function LatitudeDegreesToString (DegLatitudeValue)
' converts a latitude in degrees to a latitude string format Hddmm.mGdddmm.m
' H=N or S	G=E or W
Dim x, y, z, DegreeStr, MinuteStr, DecimalStr
x=Abs(Fix(DegLatitudeValue))
If Abs(DegLatitudeValue)>90 Then
	LatitudeDegreesToString="Error Latitude >90"
	Exit Function
End If
If Abs(DegLatitudeValue)<1 Then
	y=Round(Abs(DegLatitudeValue*60),1)
Else
	y=round((Abs(DegLatitudeValue)-x)*60,1)
End If
If y<10 Then
	MinuteStr="0"+Cstr(Fix(y))
Else
	MinuteStr=Cstr(Fix(y))
End If
z=Abs(y)-Fix(ABS(y))
If z=0 Then
	DecimalStr="0"
Else
	DecimalStr=Mid(Cstr(round(z,1)),3,1)
End If
If MinuteStr="60" Then
	MinuteStr="00"
	x=x+1
End If
If x<10 and x>=1 Then
	DegreeStr="0"+Cstr(X)
ElseIf x<1 Then
	DegreeStr="00"
Else
	DegreeStr=Cstr(x)
End If
If DegLatitudeValue>0 Then
	LatitudeDegreesToString="N"+DegreeStr+MinuteStr+"."+DecimalStr
Else
	LatitudeDegreesToString="S"+DegreeStr+MinuteStr+"."+DecimalStr
End If
End Function
Function DecHourToString (DecHourNum)
' converts a decimal hour to a time string format hh:mm
Dim  x, y, HourString, MinuteString
If DecHourNum < 0 Then
	DecHourToString = "Error time is negative"
	Exit Function
End If
x=Fix(DecHourNum)
y=(DecHourNum-x)*60
MinuteString=CStr(Round(y,0))
If MinuteString="60" Then
	MinuteString="00"
	x=x+1
End If
If x<10 Then
	HourString="0"+Cstr(x)
Else
	HourString=Cstr(x)
End If
If Eval(MinuteString) < 10 And MinuteString<>"00" Then
	MinuteString="0"+MinuteString
End If
DecHourToString = HourString+":"+MinuteString
End Function
Function Atan2 (y,x)
' Returns the arctangent of the specified x- and y-coordinates. The
' arctangent is the angle from the x-axis to a line containing the origin (0, 0)
' and a point with coordinates (y, x). The angle is given in radians
' between -pi and pi, excluding -pi.
If x>0 Then
	Atan2=ATN(y/x)
	Exit Function
End If
If x<0 And y>=0 Then
	Atan2=ATN(y/x)+pi
	Exit Function
End If
If x=0 And y>0 Then
	Atan2=pi/2
	Exit Function
End If
If x<0 And y<0 Then
	Atan2=ATN(y/x)-pi
	Exit Function
End If
If x=0 And y<0 Then
	Atan2=-pi/2
	Exit Function
End If
End Function
Function Modulus (y,x)
' calculates the remainder of y/x
If y>=0	Then
	Modulus=y-X*Fix(y/x)
Else
	Modulus=y+x*(Fix(-y/x)+1)
End If
End Function
Sub reset1_onclick
text1.value=""
text2.value=""
text3.value=""
text4.value=""
text5.value=""
text6.value=""
textarea1.value=""
checkbox2.status=False
End Sub
Sub button1_onclick
text1.value="N5128.2W00027.1"
text2.value="N3545.8E14023.4"
text3.value="31/08/2000"
text4.value="01/09/2000"
text5.value="18:00"
text6.value="05:00"
text7.value="10"
textarea1.value=""
checkbox2.status=True
End Sub