USGS MIPS Shade Documentation

USGS MIPS Shade Documentation

This program is used to correct horizontal shading problems in sidescan sonar images . Each column of samples is corrected individually and two correction methods are available. The first calculates an additive offset for each column by subtracting the average of all samples in that column from the average of the image; the second calculates a multiplicative coefficient for each column by dividing the average of the image by the average of the column. If a beam angle correction is desired use the program Snrshade.

Files

This program requires as input one unsigned 8-bit or one signed 16-bit image file and produces an output image of the same type as the input image. The following information is transferred from the input file to the output file(if appropriate):

Image labels
Mosaic labels
Projection labels
Sonar labels
Navigation file
History file

Parameters

ADD and MULT: These parameters are used to choose the type of correction to be applied to the data. The ADD option will use an additive offset and the MULT option will use multiplicative coefficients to correct for radiometric problems in the image. The default option is ADD.
NORM: This parameter can be used to override the default normalization factor of the image average; if entered the given NORM value is used instead of the image average.
MIN and MAX: These parameters are used to define the range of valid DN s. Pixels with DNs inside the MIN to MAX range, inclusive, are valid and are used to calculate the averages. Those pixels having DN values outside the range are considered invalid and are not used, but are corrected. The defaults for unsigned data are 1 and 254, respectively, and -32767 and 32766 for signed 16-bit data.
SL and EL: These parameters are used to define starting and ending lines where statistics will be gathered from for the correction. Lines outside this area are also corrected but not used to calculate the column statistics or the average of the image. This allows the user to exlude top and/or bottom image areas with noise or special start-up problems.

Examples

From left to right, image before horizontal shading correction and image after horizontal shading correction.

[Example Image]