calcEarthSunDist: Compute earth-sun distance based on day of the year
Description
The earth-sun distance for a particular day of the year is computed based on
one of several empirical formulas.
Usage
calcEarthSunDist(date, formula = c("Spencer", "Mather", "ESA"))
Arguments
date
Date of the sensor overpass; either a character string in a
native date format (e.g. "YYYY-MM-DD", see as.Date) or a POSIX*
object (see as.POSIXct).
formula
Formula to be applied, specified through the name of the
author, i.e. one of "Spencer", "Mather" or "ESA".
Value
Numeric earth-sun distance (in AU).
Details
Computation of earth-sun distance using formulas provided by
Spencer (1971), Mather (2005) or ESA.
References
The formulas are taken from the following sources:
Spencer: Spencer JW (1971) Fourier series representation of the position of
the sun. Search 2/5. Taken fromhttps://goo.gl/lhi9UI.
Mather: Paul M. Mather (2005) Computer Processing of Remotely-Sensed Images:
An Introduction. Wiley, ISBN: 978-0-470-02101-9,http://eu.wiley.com/WileyCDA/WileyTitle/productCd-0470021012.html.
ESA: ESA Earth Observation Quality Control: Landsat frequently asked questions.
See also: Bird R, Riordan C (1984) Simple solar spectral model for direct and
diffuse irradiance on horizontal and tilted planes at the Earth's surface for
cloudless atmospheres. http://www.nrel.gov/docs/legosti/old/2436.pdf.