hsdar (version 0.5.1)

rededge: Red edge parameter

Description

Derive red edge parameters from hyperspectral data

Usage

rededge(x, smooth = TRUE, round = FALSE, ...)

Arguments

x

List of class Speclib

smooth

Logical indicating if spectral data should be smoothed. See details section.

round

Logical indicating if resulting wavelength position should be rounded.

...

Further arguments passed to derivative.speclib

Value

A data frame containing parameters for each spectrum.

Details

Shape and location of the red edge are commonly described by four parameters:

• $R0$: minimum reflectance in the red spectrum
• $l0$: wavelength of the minimum reflectance
• $lp$: inflection point
• $Rs$: shoulder wavelength

The red edge parameters are calculated as proposed in Bach (1995) from the spectral area between 550 and 900 nm. $l0$ is calculated as the last root before the maximum value of the 2nd derivation. The minimum reflectance is the reflectance at ($l0$). The inflection point is the root of the 2nd derivative function between the maximum value and the minimum value. The shoulder wavelength is the first root beyond the minimum value of the 2nd derivation.

Optional smoothing is performed with

smoothSpeclib(x, method = "spline", n = round(nbands(x)/10,0))

prior to all calculations. Note that reflectance values returned by the rededge-function are original values and not the smoothed reflectances. This would not be the case, if already smoothed reflectance values are passed to rededge-function.

References

Bach, H. (1995): Die Bestimmung hydrologischer und landwirtschaftlicher Oberflaechenparameter aus hyperspektralen Fernerkundungsdaten. Muenchner Geographische Abhandlungen Reihe B, Band B21.

See Also

vegindex, derivative.speclib, smoothSpeclib

Examples

data(spectral_data)
rd <- rededge(spectral_data)
boxplot(rd$R0 ~ attribute(spectral_data)$season, ylab = "R0")