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: http://xmm.vilspa.esa.es/calibration/documentation/CALHB/node546.html
Дата изменения: Tue Sep 20 19:45:20 2011 Дата индексирования: Mon Apr 11 03:10:18 2016 Кодировка: Поисковые слова: п п п п п п п п п п п п п п п п п п п п р р р р р р р р р р р р р р р р р р |
calc_mode is set to 0:
the distortion (deltaX, deltaY) at the detector location (rawX, rawY)
is derived from the distortion map stored in the extension
FILTER-FilterId (e.g. FILTER-U, FILTER-V, FILTER-GRISM1 etc.).
As the distortion map is only coarsly sampled an interpolation is required to
derive the distortion at the requested position
(rawX, rawY).
calc_mode is set to 1:
the distortion (deltaX,deltaY) at the location (rawX, rawY) is
computed using an up to 7th order polynomial.
The coefficients of the polynomials are stored in the
columns XPOLYCOEF, YPOLYCOEF of the extension POLYNOM_MAP.
Unused coefficients are set to zero in the CCF file, e.g. if only a second order polynomial
is used, then all higher order coefficients are zero.
There is one set of coefficients (XPOLYCOEF, YPOLYCOEF) per filter element
in the POLYNOM_MAP extension.
The required binary table entry is identified by matching the
value of the column FILTER_ID with the State Variable FilterID.
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deltaX, deltaY | offset in x- and ydirection from linear grid. |
The offset is defined as difference (true - linear) position | |
X | offset from boresight in x-direction ![]() |
Y | offset from boresight in y-direction ![]() |
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coefficients of the 7th order polynomial stored in the columns |
XPOLYCOEF, YPOLYCOEF respectively. |
Interpretation of offset vector by SAS:
The offset vector (deltaX, deltaY) are used by the SAS to calculate the
angular distance of a position to the boresight in the following way.
First the linear offset (linX, linY) from the boresight
(in units of pixel) is calculated by the following equation:
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(30) |