phenex (version 1.4-5)

bise: Best index slope extraction

Description

Reduces noise in NDVI time-series. Second interpretation of bise algorithm.

Usage

bise(x, slidingperiod, growthFactorThreshold, cycleValues)

Arguments

x

An object of class ‘NDVI’ containing raw NDVI values.

slidingperiod

Sliding Period of the BISE-algorithm, default value is 40.

growthFactorThreshold

Maximum allowed increase per day as factor, default value is 0.1 (increase of 10 percent).

cycleValues

A boolean value determining whether the end of the ndvi timeserie is combined with its beginning or not (default value is true). If false, gaps or low ndvi values at the beginning of timeserie influence the resulting timeserie.

Value

An object of class ‘NDVI’ containing raw and corrected NDVI values.

Details

Knowledge regarding the phenological cycle in temperate climates and its temporal evolution is used to detect and eliminate cloud contaminated observations. As the algorithm is searching forward within daily NDVI observations over 1 year, decreases are only accepted if no higher value is found within a so called sliding period. A period of 40 days proved best for our study area but might have to be modified when study areas in different climates are investigated.

References

Viovy, N., Arino, O. and Belward, A.S. (1992). The Best Index Slope Extraction (BISE) - a method for reducing noise in NDVI time-series. International Journal of Remote Sensing, 13, 1585-1590.

See Also

modelNDVI,

Examples

	# load data
	data(avhrr)

	# create NDVI object
	ndvi <- new("NDVI", values=avhrr.ndvi/10000, year=as.integer(1995))

	# correct values (bise)
	ndvi.bise <- bise(ndvi, slidingperiod=40, growthFactorThreshold=0.1)

	#plot
	plot(ndvi.bise)