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.help dcmpf Jun99 "Slalib Package"
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SUBROUTINE slDCMF (COEFFS,XZ,YZ,XS,YS,PERP,ORIENT)
- - - - - -
D C M F
- - - - - -
Decompose an [X,Y] linear fit into its constituent parameters:
zero points, scales, nonperpendicularity and orientation.
Given:
COEFFS d(6) transformation coefficients (see note)
Returned:
XZ d x zero point
YZ d y zero point
XS d x scale
YS d y scale
PERP d nonperpendicularity (radians)
ORIENT d orientation (radians)
The model relates two sets of [X,Y] coordinates as follows.
Naming the elements of COEFFS:
COEFFS(1) = A
COEFFS(2) = B
COEFFS(3) = C
COEFFS(4) = D
COEFFS(5) = E
COEFFS(6) = F
the model transforms coordinates [X1,Y1] into coordinates
[X2,Y2] as follows:
X2 = A + B*X1 + C*Y1
Y2 = D + E*X1 + F*Y1
The transformation can be decomposed into four steps:
1) Zero points:
x' = XZ + X1
y' = YZ + Y1
2) Scales:
x'' = XS*x'
y'' = YS*y'
3) Nonperpendicularity:
x''' = cos(PERP/2)*x'' + sin(PERP/2)*y''
y''' = sin(PERP/2)*x'' + cos(PERP/2)*y''
4) Orientation:
X2 = cos(ORIENT)*x''' + sin(ORIENT)*y'''
Y2 =-sin(ORIENT)*y''' + cos(ORIENT)*y'''
See also slFTXY, slPXY, slINVF, slXYXY
P.T.Wallace Starlink 14 August 1994
Copyright (C) 1995 Rutherford Appleton Laboratory
Copyright (C) 1995 Association of Universities for Research in Astronomy Inc.
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