ISOCAM Interactive Analysis User's Manual Version 5.0 - ISO - ESA

244 CHAPTER 20. ADVANCED DATA CALIBRATION
Furthermore the size of each MOSAIC pixel is determined when the raster PDS is created
from an SSCD with get sscdraster. The size is computed to be optimum for the raster stepsize
and PFOV. This might result in rectangular, e.g. not square pixels. Setting the square
option ensures the creation of square pixels:
CIA> raster_pds = get_sscdraster( sscd, /square)
Normally the orientation of the raster MOSAIC is determined when the raster PDS is created
from an SSCD with get sscdraster: The mosaic is north oriented for north axis rasters, and
camera oriented for spacecraft axis rasters. However, the user may override this:
CIA> raster_pds = get_sscdraster( sscd, /north )
CIA> raster_pds = get_sscdraster( sscd, /camera )
1. method=‘project’
method: EXPOSUREs are corrected for FOV distortion and then projected onto the
raster MOSAIC FOV according to their individual coordinates. A C-coded program,
projection performs the actual projection.
This is probably the best method for raster MOSAIC creation. It does a good job of
taking into account all the different raster types, e.g. North axis, micro-scan. It also
works even if the actual coordinates of the EXPOSUREs do not match their intended
positions in the raster. It is the default method.
For more on projection and coadding images with different astrometry see Section
20.15.
called routine: projette and the executable projection.
2. method=‘idlproj’
method: Same method as method=‘project’, the difference being that an IDL coded
projection routine is used.
called routine: raster scan idlproj
3. method=’camera’
method: By this method the EXPOSUREs are rebinned to 256 × 256 images and then
coadded according to their position in the raster. The EXPOSUREs are always kept
aligned to ISOCAMs axes even if the raster is a NORTH axis raster – this means
that the axes of the raster MOSAIC will also be aligned to ISOCAMs axes.
This method is of most advantage when raster steps sizes are not multiples of pixel
sizes – the initial rebinning of the EXPOSUREs make the raster step size a whole
multiple of the pixel size.
called routine: raster cam
20.5 Creation of the beam-switch MOSAIC
After all the calibration steps described in Section 20.2 have been performed on a BS PDS then
the beam-switch MOSAIC maybe created. This is done with reduce bs.
The process is simple: