Skip to Content

geoshift {landsat}

    Shift and pad an image
Package: 
landsat
Version: 
1.0.8

Description

    Shifts an image vertically or horizontally and adds a padded border.

Usage

geoshift(mat, padx, pady, shiftx, shifty, nodata = NA)

Arguments

mat
    A matrix, data frame or SpatialGridDataFrame
padx
    Number of pixels to add as padding in the x direction on each side of the image (along the x-axis). Should be larger than the number of pixels to shift to avoid data loss.
pady
    Number of pixels to add as padding in the y direction on each side of the image (along the y-axis). Should be larger than the number of pixels to shift to avoid data loss.
shiftx
    Number of pixels to shift (positive or negative) in the x direction (along the x-axis).
shifty
    Number of pixels to shift (positive or negative) in the y direction (along the y-axis).
nodata
    Value to use for missing data.

Details

    This function can be used to correct spatially-referenced images that are off by a few pixels in the x or y directions. It does not warp an image, only slide it. Adding padding to the outside edge makes it possible to match several images even if they are not stored with georeferecing information. geoshift() can be used in conjunction with georef() to automatically match up geospatial images. Note: directions are relative to the image as displayed by the image() command, and not the underlying matrix representation.

Values

Returns data in the same format as the function was given: matrix, data frame, or SpatialGridDataFrame.

See Also

georef

Examples

testmat <- matrix(1:9, 3, 3)
geoshift(testmat, 5, 10, 0, 0)
geoshift(testmat, 5, 10, 2, 2)
 
# to use for georeferencing
data(nov3)
data(july3)
july.shift <- georef(nov3, july3, maxdist=50) # match july to november
july3.corr <- geoshift(july3, padx=50, pady=50, july.shift$shiftx, july.shift$shifty)
 
# only need to run georef once for a particular date
# use the same correction for all bands
data(july4)
july4.corr <- geoshift(july4, padx=50, pady=50, july.shift$shiftx, july.shift$shifty)

Author(s)

    Sarah Goslee

Documentation reproduced from package landsat, version 1.0.8. License: GPL (>= 2)