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

20.4. RASTER MOSAIC CREATION 243
Figure 20.2: The raster MOSAIC with SSCD calibration and Fouks-Schubert transient correction.
Display for comparison with Figure 3.3.
6. It might be interesting to compare the results of this calibration and those in Chapter 3
– see Figure 20.2 and Figure 3.3 respectively. Clearly in Figure 20.2 the background is
cleaner and the ghost image to the left of the source is not present.
CIA> tviso, raster_pds.raster
20.4 Raster MOSAIC creation
Final step in calibrating a raster PDS is the creation of the raster MOSAIC from the EXPO-
SUREs in .IMAGE. Four methods can be used to compute the MOSAIC, all of which are handled
by raster scan. The different methods can be selected by setting the keyword method. Ingeneral
all the methods involve a weighted averaging of EXPOSURE pixels, where the weight is the
square root of the EXPOSURE pixel weight. That is, for each EXPOSURE pixel .IMAGE[i,j,k]
the weight is taken as .NPIX[i,j,k].
In all cases the impact of raster MOSAIC creation on the PDS is the same. The field
.RASTER is filled with the computed raster MOSAIC. The fields .NPIXRASTER is filled with
the number of IMAGE pixels from which each pixel in .RASTER has been derived. The field
.RMS is filled with the RMS of these IMAGE pixels.
Note the raster MOSAIC size is determined when the raster PDS is created from an SSCD
with get sscdraster. The size is computed to be optimum for the raster step-size and PFOV.
However, the user may increase the computed size by a specified magnification factor. For
example, to have a MOSAIC which is twice as large in both dimensions as the computed size:
CIA> raster_pds = get_sscdraster( sscd, magnify=2 )