Noproj reprojects a level1 cube to correct for camera distortion. The result is a level1 cube of the undistorted image in "Ideal" camera space.

Both cubes (FROM and MATCH) must see the same target. Each requires SPICE data and should be processed with spiceinit prior to running noproj.

The Ideal camera geometry is derived from the MATCH cube. If the coordinate (lat/long) at each pixel in the MATCH cube maps to a lat/long coordinate in the FROM cube, then the pixel value at the mapped coordinate in the FROM cube is projected into the TO cube, with some interpolation due to the distortion correction. The default behavior is that any offbody pixels in the MATCH and the FROM cube are set to null in the TO cube. See OFFBODY and OFFBODYTRIM for alternative options for mapping offbody data. Also see cam2cam as noproj parameters are passed to cam2cam.

This program will modify the cube labels for the Ideal camera. The original Instrument group is renamed OriginalInstrument and a new instrument group is created for the Ideal Camera. The cube data is modified when this program runs cam2cam, creating the noproj'ed output cube with camera distortions removed.

Note that noproj will not propagate AlphaCube groups from the MATCH cube into the TO cube since noproj is resampling the image.

In this example, noproj is used to remove camera distortions from two images acquired by the OSIRIS-REx NavCam during a particle ejection event at Bennu (Lauretta et al., 2019). Example images are 20190106T205618S792_ncm_L0 (long exposure) and 20190106T205611S433_ncm_L0 (short exposure). The images are imported from FITS files and converted to ISIS cubes with tagcams2isis. Both cubes are initialized with spiceinit using the bennu_g_00880mm_alt_obj_0000n00000_v020.bds global shapemodel found in the OSIRIS-REX SPICE KERNEL bundle.

Input images

Command Line for running noproj on long exposure image

Here, OFFBODY=TRUE and OFFBODYTRIM=FALSE to preserve the pixels in the space around Bennu, including the ejected particles. Note that the same cube is used for both FROM and MATCH parameters.

Command Line for running noproj on short exposure image

Here, OFFBODY and OFFBODYTRIM are FALSE. OFFBODY is set to FALSE to set all pixels off the target body to null. The noproj'ed long exposure output is used as the MATCH cube. The specifications file (specs.pvl) is required because the MATCH cube has been run through noproj and is now identified as an "Ideal" camera in the label. The specifications file contains the undistorted (Ideal camera) detector dimensions. In this case:

            Object = IdealInstrumentsSpecifications
  
              Group = "IdealSpacecraft/IdealCamera"
                DetectorSamples = 3050
                DetectorLines = 2404
              End_Group
  
            End_Object
            End
          

Output images

Null pixels are shown in yellow to illustrate the undistorted image outline.

Mosaic the noproj'ed long and short exposures

To see the ejected particles and the surface of Bennu in the same scene, we mosaicked the short exposure cube on top of the long exposure cube using handmos. In the image shown, both noproj'ed cubes have been contrast-stretched, but only at a rudimentary level. This example does not reproduce the full processing required to generate the figure in the article referenced above, but it does illustrate a case where it is necessary to preserve off-body pixels.

Particle ejection observations mosaic

OSIRIS-REx NavCam image 20190106T205611S433_ncm_L0 combined with 20190106T205618S792_ncm_L0.

To Reproduce This Example

Download the shell script, the ray tracer preference file, and the Ideal camera specifications file linked here. The ray trace preference file sets the ray trace library to Bullet rather than NAIF DSK (default for shape models with a ".bds" file extension) as Bullet will detect occlusions. The specifications file defines the size of the distortion-corrected NavCam image, which after running noproj is identified as the "Ideal" camera model. Before running the script, place the preference and specification files in $ISISROOT. The script will download and move the OSIRIS-REx DSK (shapemodel) kernel into $ISISDATA. See the ISIS documentation for instructions on downloading $ISISDATA for a specific mission.