// This is reverse-engineering of Jim Leonard's picture of MIThenge #5145

use sun.frink
use mithengecorridor.frink

// Date from EXIF data

exifdate = #2007-01-29 16:47:46 Eastern#

// According to Lenny Foner, Jim's camera is 2 seconds ahead of GPS time
// this was also a 10 s exposure and the date was probably recorded at
// the end of exposure (?)

truedate = exifdate - 2 s - 5 s

// We don't care all that much about refraction, so the temp/pressure figures
// below may not be accurate but shouldn't matter much.
[sunAzimuth, sunAltitude] = refractedSunAzimuthAltitude[truedate, lat, long, F[29], 30.42 inHg]


// Convert Meeus azimuth conventions to normal conventions.
sunAzimuth = (sunAzimuth + 180 degrees) mod circle
println["True sun azimuth at this time was " + format[sunAzimuth,"degrees",5]]
println["Approx. altitude at this time was " + format[sunAltitude,"degrees",5]]


// Jim's camera was 39 inches right of the centerline of the fluorescents
rightoffset = 39 inches

latticewidth = 31.5 in

// The grating is offset to the right of the centerline of the corridor?
//grateOffset = (8.5 / 43) latticewidth
// grateOffset = (8.0 / 45.5) latticewidth

grateOffset = (1.5 cm / (11 cm)) latticewidth

println["The grate offset is " + format[grateOffset, "inches", 2]]

// Distance from grating
gratingDist = 460 feet + 7.5 in

// Calculate the sun radius at this time.
sunRadius = sunRadiusAngle[truedate]
println["Sun radius is " + format[sunRadius,"degrees", 5]]

azimuthOffset = arctan[rightoffset - grateOffset, gratingDist]

println["Azimuth offset is " + format[azimuthOffset,"degrees",5]]

corridorAzimuth = sunAzimuth + azimuthOffset
println["Corridor azimuth is " + format[corridorAzimuth,"degrees",3]]