ISIS 3 Application Documentation
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Stitch together multiple HiRISE CCD images
This program combines images from multiple HiRISE CCDs into a single output image file. The output file can be considered to be a special type of mosaic in which the different CCD images are placed next to each other in positions that correspond to detector numbers. The input files must each contain both channels of a single detector, which are the files produced by the "histitch" program. CCD images with lower CCD numbers are placed into the output file to the left of CCD images with higher CCD numbers. By default the CCD images are placed into the output file from left to right, i.e., in order of increasing CCD number. This order can be changed with the MosaicOrder keyword in the "shiftdef" file.
Images are inserted at locations corresponding to the relative offsets of the detectors. In most cases, pixel replication is used when processing an input image so that it matches the scale of the image with the lowest summing mode. However, if any of the input images were observed with a summing mode of 3, then pixel replication is used for all images to match the scale that would have been obtained with a summing mode of 1. No resampling of input pixel values is done.
In many cases, adjacent images do not line up vertically due to observing conditions and other factors. The SHIFTDEF parameter allows the user to apply arbitrary offsets in lines to any or all the input images so they align properly.
It has been determined that summing modes add an additional delay to imaging due to pre-cycling of the detector electronics. Typically, images have an additional 180 * (summing mode - 1) lines delay in the actual imaging of the target. These lines are unbinned, not subject to the summing mode applied during imaging. This is not an issue if all images being stitched by this application are the same summing mode. If images with different summing modes are acquired in the same observation, then this offset is automatically applied to the images with differing summing modes. This will result in adding lines of offset to some images and increasing the number of lines in the resulting output image.
The input files may contain multiple bands but all input files must contain the same number of bands. This is useful for creating color products where the input files are compatable with the constraints of this application.
The name of a file containing a list of HiRISE image files to be stitched together. Each file should be listed on a separate line.
This file contains objects for each CCD and for each combo of binning/tdi that requires a modification to its placement in the mapping of the HiRISE focal plane. The name of each object is the CCD name for which the shift in line or sample is needed. For example, the leftmost CCD, CCD 0 is named "RED0", the next "RED1" and so on. The binning/tdi groups are named by combining the binning and tdi mode. For example, summing=1 and tdi=64 the group would be "1/64". Hiccdstitch searches for names of objects that match the stitched input cube files ccd then for the proper combo of summing and tdi. If the group for summing/tdi isn't found, values from the ccd object will be used. These offsets will be applied to the default sample and line location of where the CCD is mapped to in the focal plane.
Offsets for both line and sample can be supplied. None, one or both can be provided for any CCD. Negative values shift the image left if a sample offset is given or up if a line offset is given. Positive values in sample and line shift the image right and down, respectively.
These shifts are absolute shifts and only apply to the specified CCD and are not propagated to subsequent CCDs left to right in the focal plane layout. (HiRISE CCD arrangement is always left to right as far as hiccdstitch is concerned, unless overiridden by the MosaicOrder keyword.) For example, if stitching all 10 RED CCDs in an image you find that RED5 must be shifted left 20 pixels but all other CCDs line up file to the right, meaning RED6 through RED9, then you are required to privide groups for RED6, RED7, RED8 and RED9 with the same SampleOffset provided for RED5. This is the only way proper sample alignment is retained.
Below is an example of the format of the input file for the SHIFTDEF file:
Object = Hiccdstitch # Defaults for Red0 images Object = RED0 SampleOffset = -10 LineOffset = 5 # Summing=1, Tdi=64 values. Any of the three keywords (MosaicOrder, SampleOffset, LineOffset) # can exist in the summing/tdi groups that will override the defaults in the RED0 object. Group = 1/64 SampleOffset = 0 LineOffset = 0 End_Group # Summing=1, Tdi=128 Group = 1/128 SampleOffset = 20 End_Group # If a summing/tdi group does not exist, the ccd defaults are used End_Object Object = RED3 SampleOffset = 13 LineOffset = -5 End_Object Object = RED5 LineOffset = 22 End_Object Object = RED9 # MosaicOrder of -1, indicates the ccd is placed in mosaic first. MosaicOrder = -1 End_Object Object = IR11 SampleOffset = -4 LineOffset = 2 End_Object Object = BG12 SampleOffset = 12 End_Object End_Object End
The only keywords that hiccdstitch reads from this file are SampleOffset , LineOffset and MosaicOrder. All other keywords are ignored. All CCD objects must be contained within the Hiccdstitch object.
Note that this file is an optional parameter. If it is not provided, then all CCD files provided are mapped to focal plane positions as specified in the HiRISE Instrument Operations Handbook. Note that the size of a HiRISE pixel is 0.012 millimeters and the measurements in the handbook are also in millimeters.
The output cube into which the input cubes will be placed.
If provided, the actual line and sample locations of each CCD as they map to the TO cube are recorded here. This format is the the same as the format provided in the STITCHDEF file.
This is the type of interpolation to be performed on the input when ccds of different summing modes are combined.