declination: Compute declination angle

In environmentalinformatics-marburg/satelliteTools: What the package does (short line)

Description

Compute the declination of the sun at solar noon based on the day of the year.

Usage

declination(n, formula = c("Cooper", "Spencer"), unit = c("radians",
  "degrees"))

Arguments

n	Day of the year (DOY) as integer or Date from which to derive DOY.
formula	character, formula from which to calculate the angular declination of the sun, specified through the name of the author (see References). Currently, the approximation equation from Cooper (1969) and the more accurate version from Spencer (1971) are available.
unit	character, determines whether to return the declination angle in radians (default) or degrees.

Value

A numeric declination angle.

Note

"The declination of the sun is the angle between the equator and a line drawn from the centre of the Earth to the centre of the sun." (directly taken from http://www.pveducation.org/pvcdrom/properties-of-sunlight/declination-angle)

References

The formulas are taken from the following sources:

• Cooper: Cooper PI (1969) The absorption of radiation in solar stills. Solar Energy 12(3), 333–346, http://www.sciencedirect.com/science/article/pii/0038092X69900474.

• Spencer: Spencer JW (1971) Fourier series representation of the position of the sun. Search 2(5), 172, https://goo.gl/lhi9UI.

See also

• Duffie JA, Beckman WA (2013) Solar Engineering of Thermal Processes. Wiley: Hoboken, New Jersey, ISBN: 978-0-470-87366-3, http://eu.wiley.com/WileyCDA/WileyTitle/productCd-0470873663.html and

• ITACA (2016) Part 3: Calculating Solar Angles. Available online at http://www.itacanet.org/the-sun-as-a-source-of-energy/part-3-calculating-solar-angles/

for further information.

Examples

## calculate current declination angles
sapply(c("Cooper", "Spencer"), function(frml) {
  declination(Sys.Date(), formula = frml)
})

environmentalinformatics-marburg/satelliteTools documentation built on May 16, 2019, 8:16 a.m.