GCdistance              Great circle distance
JD                      Julian Day from POSIXct
JDymd                   Julian Day from yyyy, mm, dd
aspect                  Aspect or orientation of the slope
cgrad                   Normal vector to every grid cell in a DEM
daydoy                  Dates to day of the year
daylength               Length of daylight
declination             Declination
degrees                 Radians to degrees
doshade                 Cast shadows
doyday                  Day of the year to date
eqtime                  Equation of time
hillshading             Intensity of illumination over a surface
hourangle               Hour angle
insol-package           Solar Radiation
insolation              Direct and diffuse solar radiation.
meteoandes              Mountain meteorological data
normalvector            Vector normal to surface
p2rho                   Air pressure to density
radians                 Degrees to radians
rh2sh                   Relative humidity to specific humidity
slope                   Slope of grid cells in a DEM
sunpos                  Azimuth and zenith of the Sun
sunr                    Earth radius vector
sunvector               Solar vector
wvapsat                 Saturation pressure of water vapor
z2p                     Altitude to pressure
