psEhlers: Pan sharpen low resolution satellite channels by using the...

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

Description

Pan sharpen low resolution satellite channels by using the high resolution panchromatic channel using a combination of IHS transformation and fourier filtering as proposed by Ehlers (2004).

Usage

## S4 method for signature 'Satellite'
psEhlers(x, res.method = "ngb", filter = list(win =
  "Han", frq.lowpass = NULL, frq.highpass = NULL), padzero = FALSE,
  subset = FALSE)

## S4 method for signature 'RasterStack'
psEhlers(x, PAN, res.method = "ngb",
  filter = list(win = "Han", frq.lowpass = NULL, frq.highpass = NULL),
  padzero = FALSE, subset = FALSE)

Arguments

x	Satellite or raster::Raster* object.
res.method	resampling method to be used for the xs channels. Currently methods of resample, namely "ngb" and "bilinear" are allowed.
filter	list object for defining filter window type and further filter parameters. Currently only Han window is implemented and cut of frequency is calculated by resolution ratio of xs to PAN resolution automatically.
padzero	Logical; defaults to FALSE. Option to zero pad images before applying FFT. Currently only images with even number of rows and columns can be zero padded. If zero padding is choosen images need to be cropped to have even numer of rows and columns (see crop). By default if number of rows/ columns are uneven but padding ist set to TRUE function will warn but continue without padding. For information on zero padding see for example Butz (2011) in References.
subset	Logical; if TRUE, all layers except for the cropped ones are being dropped; if FALSE, the cropped layers are being appended to the Satellite object.
PAN	A raster::RasterLayer object of the panchromatic channel.

Details

This function implements the PAN sharpening algorithm described in Klonus & Ehlers (2007) and Ling et. al. (2007). It sharpens satellite images by using a combination of IHS transformation and subsequent filtering of the Intensity component in the frequency domain. After filtering of the intensity components of PAN and XS the images are reverse FFT transformed and summed up to form the new intensity component to be used for the reverse IHS transformation, which results in the new pansharpened RGB channels. For more detailed description see references.

Value

If x is a Satellite object, a Satellite object (with added pansharpened layers); if x is a raster::stack* object, a raster::stack* with pansharpened layer(s).

References

Ehlers, M., 2004: Spectral characteristics preserving image fusion based on Fourier domain filtering. Vol. 5574 of, 1-13 http://dx.doi.org/10.1117/12.565160 (Accessed July 26, 2015).

Klonus, S., and M. Ehlers, 2007: Image Fusion Using the Ehlers Spectral Characteristics Preservation Algorithm. GIScience & Remote Sensing, 44, 93-116, doi:10.2747/1548-1603.44.2.93.

Ling, Y., M. Ehlers, E. L. Usery, and M. Madden, 2007: FFT-enhanced IHS transform method for fusing high-resolution satellite images. ISPRS Journal of Photogrammetry and Remote Sensing, 61, 381-392, doi:10.1016/j.isprsjprs.2006.11.002.

Fisher, R, et. al. 2000: HYPERMEDIA IMAGE PROCESSING REFERENCE. http://homepages.inf.ed.ac.uk/rbf/HIPR2/fourier.htm

Weinhaus, F., 2011: ImageMagick v6 Examples – Fourier Transforms. http://www.imagemagick.org/Usage/fourier/#im_fft

Butz, T., 2011: Fouriertransformation fuer Fussgaenger. 7., aktualisierte Aufl. Vieweg + Teubner, Wiesbaden. (German)

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