astro {tripEstimation} | R Documentation |
This set of functions provides simple position calculations for the sun and moon, taken from Pascal routines published in Montenbruck and Pfleger (1994, Dunlop).
These are completely independent from the (specifically optimized) solar elevation calculations available via [elevation and solar].
astro(lon, lat, astro.calc) EQUHOR(DEC, TAU, PHI) FRAC(x) LMST(MJDay, LAMBDA) lunar(time) mini.sun(time) MJD(date) POLAR(X, Y, Z)
lon |
vector of lon gitudes |
lat |
vector of lat itudes |
astro.calc |
list object containing RA right ascension |
DEC |
declination |
TAU |
TAU |
PHI |
PHI |
x |
number |
MJDay |
modified julian day |
LAMBDA |
LAMBDA |
time |
vector of date-times in POSIXct format |
date |
vector of date-times in POSIXct format |
X |
x-coordinate |
Y |
y-coordinate |
Z |
z-coordinate |
astro
returns a list object with the components of the moon or sun's
position,
r |
rho component |
theta |
theta component - elevation |
phi |
phi component - azimuth |
I don't get perfect matchup with the NOAA routines for solar elevation. This may be the limitations of the (mini-versions of the) algorithms, as they are good at near-horizon (for rising and setting). Some of this could be faster (particularly the use of LMST in "astro" is not precalculated)
Michael D. Sumner
@BOOK{, title = {Astronomy on the Personal Computer}, publisher = {Springer-Verlag, Berlin}, year = {1994}, author = {Oliver Montenbruck and Thomas Pfleger}, edition = {2 (translated from German by Storm Dunlop)}, }
See Also elevation
## the moon tm <- Sys.time() + seq(by = 3600, length = 100) moon <- lunar(tm) rtp <- astro(147, -42, moon) op <- par(mfrow = c(2,1)) plot(tm, rtp$theta, main = "lunar elevation, Hobart") plot(tm, rtp$phi, main = "lunar azimuth, Hobart") par(op) ## the sun tm <- Sys.time() + seq(by = 3600, length = 100) sun <- mini.sun(tm) rtp <- astro(147, -42, sun) op <- par(mfrow = c(2,1)) plot(tm, rtp$theta, main = "solar elevation, Hobart") plot(tm, rtp$phi, main = "solar azimuth, Hobart") par(op) ## Not run: elev.gmt <- mkElevationSeg(1, tm) plot(tm, rtp$theta, main = "solar elevation mini.sun versus NOAA") lines(tm, elev.gmt(1, 147, -42)) ## End(Not run)