getElevation: Calculate the appropriate sun elevation angle for known...

In slisovski/GeoLight: Analysis of Light Based Geolocator Data

Calculate the appropriate sun elevation angle for known location

Description

Function to calculate the sun elevation angle for light measurements at a known location and the choosen light threshold.

Usage

getElevation(
  tFirst,
  tSecond,
  type,
  twl,
  known.coord,
  method = "log-norm",
  plot = TRUE
)

Arguments

tFirst	vector of sunrise/sunset times (e.g. 2008-12-01 08:30).
tSecond	vector of of sunrise/sunset times (e.g. 2008-12-01 17:30).
type	vector of either 1 or 2, defining tFirst as sunrise or sunset respectively.
twl	data.frame containing twilights and at least tFirst, tSecond and type (alternatively give each parameter separately).
known.coord	a SpatialPoint or matrix object, containing known x and y coordinates (in that order) for the selected measurement period.
method	the function can either estimate the sun elevation angle and the twilight error parameters using a log-normal ("log-norm") or a gamma ("gamma") error distribution. It is recommended to try both and evaluate the fit using the plot.
plot	logical, if TRUE a plot will be produced.

Details

NEW: The function provides two different sun elevation angle. The first (a1) refers to the median twiligth error and is needed for threshold based locaiton estimation (e.g. coord). The second (a0) refers to the zero elevation angle of the twilight error distribution and is required for e.g. mergeSites2, siteEstimate. The function also provides the parameters (log.mean and log.sd) of the fitted log-normal distribution (see red line in plot),

Author(s)

Simeon Lisovski

References

Lisovski, S., Hewson, C.M, Klaassen, R.H.G., Korner-Nievergelt, F., Kristensen, M.W & Hahn, S. (2012) Geolocation by light: Accuracy and precision affected by environmental factors. Methods in Ecology and Evolution, DOI: 10.1111/j.2041-210X.2012.00185.x.

Examples

data(calib2)
  calib2$tFirst  <- as.POSIXct(calib2$tFirst, tz = "GMT")
  calib2$tSecond <- as.POSIXct(calib2$tSecond, tz = "GMT")
getElevation(calib2, known.coord = c(7.1,46.3))

slisovski/GeoLight documentation built on Feb. 29, 2024, 2:10 p.m.