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: http://xmm.vilspa.esa.es/sas/7.1.0/doc/bkgfit/node6.html
Дата изменения: Mon Jul 9 08:51:15 2007 Дата индексирования: Sat Dec 22 07:59:37 2007 Кодировка: Поисковые слова: hst |
The fitting procedure will only converge to a unique solution if the components are linearly independent. A measure of this is the quantity
If one thinks of each image as a vector in an
dimensional space, then
is the cosine of the angle between
and
. The task calculates
for each pair of component images and fails with an error if any
is greater than 0.99. NOTE that the sums in equation 4 are carried out on unmasked pixels only. Hence components may be linearly independent in masked pixels yet still fail the
test within the task.
The task also fails if any of the components has only zero-valued pixels. Finally, since the Poisson image values are necessarily all , negative values are not allowed in the model components.