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ISIS Documentation

findgaps

Finds the gaps in a given Cube.

This program finds gaps in the line direction of an image, and will report the gap information or expand the gap based on user parameters or default settings. Gaps are areas where the entire line consists of NULL pixel values or pixel values statistically below the threshold setting of the CORTOL parameter. This program ignores single line gaps.If the LOG parameter is specified, the starting and last line of each gap as well as the band number is recorded and placed into a log filename (.pvl, .txt) entered by the user. If the output cube or TO parameter is not specified, then the program only identifies the gaps.

The CORTOL parameter should be set to "0.0" to only identify an entire line of "NULL" pixels as a gap. If the CORTOL parameter is set to a value greater than "0.0," then the statistics of the current line are compared against the statistics of the previous line to determine if the line should be considered a gap. This option is useful if random lines are much brighter or darker than the adjacent lines.

Categories

History

Christopher Austin2007-11-26 Original version
Steven Lambright2008-05-12 Removed references to CubeInfo
Kimberly Oyama and Steven Lambright2012-06-15 Added the option to nullify a gap and add a buffer of null lines above and below each gap and output these results to a cube. If no output cube is specified results will only be output to a log file (.pvl, .prt, or .txt) or vice versa. Neither output affects the other. Fixes #582.

Parameters

Files

Input cube file to be checked for line gaps.
Type cube
File Mode input
Filter *.cub

The resulting cube with a null buffer above and below each gap. Enter "TO=none" if you do not want to output a modified cube.
Type cube
File Mode output
Default none
Filter *.cub

The output file to which all of the gap information is written. If left as the default, no log file will be created/updated. This file will not be affected by the nulled lines that are included in the output cube.
Type filename
File Mode output
Default none
Filter *.txt *.prt *.pvl

Correlation Coefficient Tolerance

This parameter determines how similar one line can be to the next and still be considerd part of a gap. A higher tolerance will result in gaps that are more similar to the surrounding area (possibly valid data). A tolerance closer to zero will result in gaps that are more different from the surrounding area (CORTOL=0.0 will give you gaps of null data).
Type double
Default 0.0

Buffer Size (Lines)

This parameter specifies how many lines above the gap are set to null in the output cube.
Type integer
Default 7

This parameter specifies how many lines below the gap are set to null in the output cube.
Type integer
Default 7

Example 1

Finds Image Gaps

This example shows how findgaps works on the cube I02025005RDR.cub.

Command Line

Searches I02025005RDR.cub for gaps based on the default Correlation Tolerance of CORTOL=0.0
findgaps FROM=I02025005RDR.cub TO=cubeResults.cub LOG=logFileResults.txt ABOVE=10 BELOW=10

Input Image

I02025005RDR.cub

A section of the input cube

I02025005RDR.cub

Parameter Name: FROM

This image shows three null gaps.

Data File

Links open in a new window.
logFileResults.txt

In the case of no gaps, the LOG output file parameter will be empty.

When there are gaps in the cube image, then the gap information is reported in the LOG file if it is specified. In this example, that file is logFileResults.txt, as shown here. Each gap is displayed as a group consisting of the band number, the starting line number, the correlation coefficient that defined the line as gap, and the last line for a particular gap.

Output Image

cubeResults.cub

The same section as that shown for the input image.

cubeResults.cub

Parameter Name: TO

This is the image cubeResults.cub that has null lines above and below each gap. You can see that 10 lines above and below the gap have been nulled out. The narrow strip of valid data in the middle of the image has been set to null due to the ABOVE and BELOW parameter settings. Reduce the value for ABOVE and BELOW to minimize the lines being set to NULL.