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Dear IRAF experts,How is the size of the output transformed image calculated when using GEOMAP/GEOTRAN to align?I have 2 images, the reference is (5951 x 5992), the image to be aligned is (2011 x 1970).lapr GEOMAP:
input = "nd200031.xymatch" The input coordinate files
database = "geomap.db" The output database file
xmin = 1.0 Minimum x reference coordinate value
xmax = 6000.0 Maximum x reference coordinate value
ymin = 1.0 Minimum y reference coordinate value
ymax = 5000.0 Maximum y reference coordinate value
(transforms = "") The output transform records names
(results = "hello.res") The optional results summary files
(fitgeometry = "rotate") Fitting geometry
(function = "polynomial") Surface type
(xxorder = 2) Order of x fit in x
(xyorder = 2) Order of x fit in y
(xxterms = "half") X fit cross terms type
(yxorder = 2) Order of y fit in x
(yyorder = 2) Order of y fit in y
(yxterms = "half") Y fit cross terms type
(maxiter = 0) Maximum number of rejection iterations
(reject = 3.0) Rejection limit in sigma units
(calctype = "real") Computation type
(verbose = yes) Print messages about progress of task ?
(interactive = no) Fit transformation interactively ?
(graphics = "stdgraph") Default graphics device
(cursor = "") Graphics cursor
(mode = "ql") lapr GEOTRAN: input = "nd200031.fits" Input data
output = "rnd200031.fits" Output data
database = "geomap.db" Name of GEOMAP database file
transforms = "nd200031.xymatch" Names of coordinate transforms in database file
(geometry = "geometric") Transformation type (linear,geometric)
(xin = INDEF) X origin of input frame in pixels
(yin = INDEF) Y origin of input frame in pixels
(xshift = INDEF) X origin shift in pixels
(yshift = INDEF) Y origin shift in pixels
(xout = INDEF) X origin of output frame in reference units
(yout = INDEF) Y origin of output frame in reference units
(xmag = INDEF) X scale of input picture in pixels per reference unit
(ymag = INDEF) Y scale of input picture in pixels per reference unit
(xrotation = INDEF) X axis rotation in degrees
(yrotation = INDEF) Y axis rotation in degrees
(xmin = INDEF) Minimum reference x value of output picture
(xmax = INDEF) Maximum reference x value of output picture
(ymin = INDEF) Minimum reference y value of output picture
(ymax = INDEF) Maximum reference y value of output picture
(xscale = 1.0) X scale of output picture in reference units per pixel
(yscale = 1.0) Y scale of output picture in reference units per pixel
(ncols = INDEF) Number of columns in the output picture
(nlines = INDEF) Number of lines in the output picture
(xsample = 1.0) Coordinate surface sampling interval in x
(ysample = 1.0) Coordinate surface sampling interval in y
(interpolant = "poly5") Interpolant
(boundary = "constant") Boundary extension (nearest,constant,reflect,wrap)
(constant = 0.0) Constant boundary extension
(fluxconserve = yes) Preserve image flux?
(nxblock = 512) X dimension of working block size in pixels
(nyblock = 512) Y dimension of working block size in pixels
(verbose = yes) Print messages about the progress of the task
(mode = "ql")
the size of the output frame, rnd200031.fits, is 3500 x 3500. No matter what I give as xmax, ymax in GEOMAP, the size of the output image after GEOTRAN is always 3500 x 3500. Why is that? According to the help on GEOMAP xmax and ymax define the range over which the transformation is valid. According to GEOTRAN, the output image size is computed as
[code:1:86e07a0a74]
ncols = ncols (inimage)
if (xscale == INDEF)
xscale = (xmax - xmin ) / (ncols - 1)
else
ncols = (xmax - xmin) / xscale + 1

nlines = nlines (inimage)
if (yscale == INDEF)
yscale = (ymax - ymin ) / (nlines - 1)
else
nlines = (ymax - ymin) / yscale + 1
[/code:1:86e07a0a74] Since xscale and yscale are set to 1 in GEOTRAN, then ncols and nlines should be computed byncols = (xmax - xmin) / xscale + 1
nlines = (ymax - ymin) / yscale + 1which means they should be exactly the xmax and xmin values I define in GEOMAP. Why aren't they? Where does 3500 come from? Nothing I add or subtract gives me exactly 3500, so I'm a little puzzled. The input to GEOMAP, nd200031.xymatch contains:
2457.40 2774.15 496.25 1711.02
2451.38 2688.90 490.34 1625.80
2612.16 2029.02 651.18 965.29
3123.07 2565.28 1162.14 1501.96
3257.87 2449.99 1297.00 1386.35
3307.30 2664.86 1346.21 1601.07
3612.16 2710.67 1651.17 1646.72in the usual order, refx, refy, xin, yinThe database from GEOMAP looks like this:
# Tue 17:33:21 17-Feb-2009
begin nd200031.xymatch
xrefmean 2974.477
yrefmean 2554.696
xmean 1013.47
ymean 1491.173
geometry rotate
function polynomial
xshift -1961.984
yshift -1062.385
xmag 1.
ymag 1.
xrotation 0.02192445
yrotation 0.02192445
xrms 0.165737
yrms 0.2337971
surface1 11
3. 3.
2. 2.
2. 2.
0. 0.
1. 1.
6000. 6000.
1. 1.
5000. 5000.
-1961.984 -1062.385
0.9999999 -3.826538E-4
3.826538E-4 0.9999999
surface2 0
So, why 3500x3500? I would appreciate any insight you can offer into this matter. Thank you in advance for your time.

Nevermind, I seem to have it under control now.