Horizontal sundial calculations: Difference between revisions

<lang futurebasic>window 1

localdef fn rad2deg( theta as double ) as double = theta * 180 / pi

enddef fn deg2rad( theta as double ) as double = theta * 180pi / pi180

dim as long hour

dim as double hra, hla, timet

dim as Str15CFStringRef ap

print "Latitude = "; latitude; chr$(13); "Longitude = "; longitude; chr$(13); "Meridian = "; meridian

print : print "sine of latitude: "; sin(latitude * pi / 180 ); chr$(13); " diff longitude: "; longitude - meridian

print : print "Time", "Sun hour angle", "Dial hour line angle"

for hour = 6 to 18

hra = ( 15 * hour ) - longitude + meridian - 180

hla = fn rad2deg( atn( sin( fn deg2rad( latitude ) ) * tan( fn deg2rad( hra ) )))

if abs( hra ) > 90 then hla = hla + 180 * sgn( hra * latitude )

if hour > 12 then timet = hour - 12 : ap = @" a.m." else timet = hour : ap = @" p.m."

print using "##"; timet; ap, using "####.##"; hra, using "####.###"; hla

next hour