diff options
Diffstat (limited to 'vo/votools/gasplib/eqtopix.x')
| -rw-r--r-- | vo/votools/gasplib/eqtopix.x | 43 |
1 files changed, 43 insertions, 0 deletions
diff --git a/vo/votools/gasplib/eqtopix.x b/vo/votools/gasplib/eqtopix.x new file mode 100644 index 00000000..569f8699 --- /dev/null +++ b/vo/votools/gasplib/eqtopix.x @@ -0,0 +1,43 @@ +include <math.h> +define SZ_CDMTX 4 + +# EQTOPIX -- procedure to obtain pixel coordinates from the equatorial +# ones, giving the center position and scale of the frame. + +procedure eqtopix (plt_ra_cen, plt_dec_cen, plt_x_cen, plt_y_cen, + cdmtx, ra, dec, x, y) + +double plt_ra_cen # Plate centre (radians) +double plt_dec_cen # " " +double plt_x_cen # Plate center in x (pixels) +double plt_y_cen # Plate center in y (pixels) +double cdmtx[SZ_CDMTX] # CD Matrix (cd11, cd12, cd21, cd22) +double ra # Objects RA position (radians) +double dec # Objects DEC position (radians) +double x # Position from centre (pixels) +double y # " + +double xi # Standard coordinate (degrees) +double eta # " +double det, cd11, cd12, cd21, cd22 +double xi_arcs, eta_arcs # Standard coord. in arc seconds. + +begin + + cd11 = cdmtx[1] + cd12 = cdmtx[2] + cd21 = cdmtx[3] + cd22 = cdmtx[4] + + det = (cd11*cd22 - cd21*cd12) + call treqst (plt_ra_cen, plt_dec_cen, ra, dec, + xi_arcs, eta_arcs) + xi = xi_arcs/3600.0 # To degrees + eta = eta_arcs/3600.0 # To degrees + # Calculate x[i] and y[i] by solving the linear equations: + # xi = cd11(X-Xo) + cd12(Y-Yo) + # eta = cd21(X-Xo) + cd22(Y-Yo) + + x = (cd22*xi - cd12*eta)/det + plt_x_cen + y = (cd11*eta - cd21*xi)/det + plt_y_cen +end |