vik7track Documentation

vik7track - Zero Missing track information in EDR Viking image
This program corrects a problem which rarely occurs in EDR Viking
orbiter images. Some Viking images have spurious pixel values found in
increments of seven pixels along a scan line for all of the lines in a
frame. Visually, these spurious data are seen as vertical lines spaced
every seven pixels in an image. The problem occurs because of the way
Viking images were transmitted to Earth.  On the spacecraft, an image
is broken into 7 tracks, each track contains every seventh value
along a scan line. If telemetry errors occurred while a track was
transmitted to Earth, then the track contains spurious data values.
Sometimes, several tracks are missing.

The TRACK parameter specifies sample positions in a line which
correspond to missing tracks. Up to four sample positons can be
specified. (If more than four tracks are missing, the image data is
unusable.)   For example, if TRACK=1,4 is specified then the pixels
zeroed are 1,8,15,22,... and 4,11,18,25,... for all of the lines in the
image.

After running 'vik7track' the zeroed data can be interpolated with the
FLT8B program using the FILTER=LPFZ option and a window size of 5 lines
and 5 samples. The procedure VIKFIXTRK will execute both the 'vik7track'
and the FLT8B program. (see VIKFIXTRK.PDF documentation for details)

Visual inspection of an EDR Viking image frame determines if the frame
contains spurious data in a track.  If there are vertical stripes spaced
every seven pixels along a scan line, then you will need to run
'vik7track', or the VIKFIXTRK procedure. In order to determine the TRACK
values to enter, display an image with the TVIN program, then run TVLIST
to obtain sample positions of the spurious data.

Determine a sample position of a problem track.  For example, you might
find that there are two tracks missing in the image frame, and sample
positions 121 and 125 always have spurious values for all the lines.
Provide the two sample positions to 'vik7track' and the program will de-
termine which set of tracks are missing. For example, with
TRACK=(121,125) as input, the program determines that tracks 2 and 6 are
spurious and will zero all of the pixels in a line which correspond to
these tracks.

PROGRAMMER:  K Teal Thompson

INPUT IMAGE FILE NAME

NONE

OUTPUT IMAGE FILE NAME

NONE

TRACKS (PIXEL COLUMNS)
CONTAINING BAD DATA

NONE

Input subcube specifier

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ADDITIONAL NOTES:

Parm	Description
FROM	The image file that is to be changed. The bit type must be 8 bit data.
TO	The image file created by 'vik7track'.
TRACK	Enter one to four track values. (If more than four tracks of a VIKING frame are spurious then the image becomes unusable.) Specify any sample position in a line which corresponds to a spurious track. For example, a user dis- plays an image on the interactive display and determines that the sample positons 121 and 125 are spurious for all of the lines. The user would then enter TRACK=(121,125). The program determines that these sample positions correspond to tracks 2 and 6 in the image and thus zeros the appropriate samples.
SFROM	SFROM specifies the subcube using a single string for all three dimensions of the cube. The order of the three dimensions is always "samples:lines:bands". If a dimension is left blank, all the data for that dimension is selected. The default value of NULL for SFROM selects the entire cube. Any application below can be used for any dimension. To select specific data from any dimension: "10-100(3):11,12,15-20:1-10(2)" = This example will select every third sample starting with sample 10 thru 100. It selects lines 11 and 12, and 15-20. It selects every other band, starting with band 1 thru 10. There are special characters that can be used for selecting a subcube efficiently, such as "*","#", and "~". For examples type "help sfrom" in TAE. **NOTE** For more examples and explanation of the many features of the SFROM parameter, tutor the sfrom.pdf or refer to Introduction To ISIS, Section 6, of the ISIS User's Manual **