ISIS Application Documentation
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Null furrowed pixels
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Description
The original version of the program works by finding the correlation
between the columns in an input image. With a Channel 0 image, the first
five columns are examined; in a Channel 1 image, the last five columns are
examined (Channel 2 images are not supported).
If the statistical results suggest a furrow is detected (i.e. the correlation between two columns is below a certain threshold), then the affected column is replaced with Null pixels. If an input image does not have a furrow, none of its pixels will be altered. The label of all output files will include a new group called "Correlations." This group lists the correlations between the relevant columns. For example, "Column3to2 0.987..." means there is a strong positive correlation between columns 2 and 3 (and very unlikely to have a furrow in the area).
For the newer version, the processing has been taken from the Version 1.42 of the original HiCal pipeline perl script and processes images with summing modes 2 and 4 only.
Furrows are checked only in the columns which are based on Channel and the Summing mode. Each specified column will have a Threshold DN based on the Summing mode and CcdId. Then the starting sample and number of samples in the specified columns are determined based on the Summing mode and Channel. The DN value of pixels in these samples are checked to be in the 0 and respective Threshold range. If not, they are determined to be a furrow and set to NULL. If a furrow was found, then trimfilter and lowpass(if option is set) are run on the image in a pipeline to smooth the edges which were Nulled due to the furrows.
If the statistical results suggest a furrow is detected (i.e. the correlation between two columns is below a certain threshold), then the affected column is replaced with Null pixels. If an input image does not have a furrow, none of its pixels will be altered. The label of all output files will include a new group called "Correlations." This group lists the correlations between the relevant columns. For example, "Column3to2 0.987..." means there is a strong positive correlation between columns 2 and 3 (and very unlikely to have a furrow in the area).
For the newer version, the processing has been taken from the Version 1.42 of the original HiCal pipeline perl script and processes images with summing modes 2 and 4 only.
Furrows are checked only in the columns which are based on Channel and the Summing mode. Each specified column will have a Threshold DN based on the Summing mode and CcdId. Then the starting sample and number of samples in the specified columns are determined based on the Summing mode and Channel. The DN value of pixels in these samples are checked to be in the 0 and respective Threshold range. If not, they are determined to be a furrow and set to NULL. If a furrow was found, then trimfilter and lowpass(if option is set) are run on the image in a pipeline to smooth the edges which were Nulled due to the furrows.
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Related Objects and Documents
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Parameter Groups
Files
| Name | Description |
|---|---|
| FROM | Input file |
| TO | Output cube |
| NEW_VERSION | Updated furrows functionality from the hical pipeline |
Furrow parameters
| Name | Description |
|---|---|
| CORRELATION | Correlation threshold |
Options
| Name | Description |
|---|---|
| LOWPASS | Run Lowpass filter if Furrows are found |
Files: FROM
Description
The cube to be corrected
| Type | cube |
|---|---|
| File Mode | input |
| Filter | *.cub |
Files: TO
Description
The resultant cube containing the modified data.
| Type | cube |
|---|---|
| File Mode | output |
| Filter | *.cub |
Files: NEW_VERSION
Description
This option uses the updated furrows functionality from the hical pipeline script version1.42
| Type | boolean |
|---|---|
| Default | FALSE |
| Exclusions |
|
| Inclusions |
|
Furrow parameters: CORRELATION
Description
The maximum correlation from pixel to pixel. If the correlation between two pixels suddenly drops below this value, then a furrow has been detected.
| Type | double |
|---|---|
| Default | 0.75 |
| Minimum | 0.0 (inclusive) |
| Exclusions |
|
Options: LOWPASS
Description
Run Lowpass filter if Furrows are found
| Type | boolean |
|---|---|
| Default | true |
History
| Sean Crosby | 2007-04-03 | Original version |
| Steven Lambright | 2008-05-12 | Removed references to CubeInfo |
| Sharmila Prasad | 2011-09-02 | Added newer version of implementing hifurrows taken from the Version 1.42 of the original HiCal pipeline perl script. |