Документ взят из кэша поисковой машины. Адрес
оригинального документа
: http://xmm.vilspa.esa.es/sas/7.1.0/doc/eregionanalyse/node8.html
Дата изменения: Mon Jul 9 10:18:11 2007 Дата индексирования: Sat Dec 22 14:00:24 2007 Кодировка: Поисковые слова: annular |
In celestial coordinates a circular or annular region is actually elliptical due to the sperical geometry. To avoid conceptual problems related to this, in these special cases the region is converted internally into sky (X/Y) coordinates so that it remains circular and maintains the same size on the tangential image projection as the user might expect.