FRMDXYR

Name

frmdxyr

Purpose

Given two lists of source on field, find the dx,dy,dr offset between lists.

Description

Calling Sequence

frmdxyr,x1,y1,x2,y2,thetamin,thetamax,dtheta,xoff,yoff,theta,error

Inputs

x1 - X coordinate from list 1, in pixels.
y1 - Y coordinate from list 1, in pixels.
The first list is the one that is manipulated to get a match.
The second list is not touched.
x2 - X coordinate from list 2, in pixels.
y2 - Y coordinate from list 2, in pixels.
thetamin - Minimum angle in search range (degrees)
thetamax - Maximum angle in search range (degrees)
dtheta - Angle step size (degrees). A 0.1 degree step size is fine
for 2048x2048 data but smaller steps sizes may be necessary
for larger arrays.

Optional Input Parameters

Keyword Input Parameters

FNDRAD - passthrough to frmdxdy
NX - maximum extent in X to consider (default is max([x1,x2]))
NY - maximum extent in Y to consider (default is max([y1,y2]))
NOTE: if either list of x,y are negative, they are first shifted
so that nothing is negative. The default will make the center of
the union of the lists be the center of rotation.
MAXERR - maximum error allowed in initial spread test of position.
(default=3)
SILENT - Flag, if set will suppress all printed output to the screen
TOLERANCE - tolerance on the best angle (degrees). Default=0.01 deg.
SCALEFAC - Passed through to frmdxdy (see that routine for further
discussion).

Outputs

xoff - X offset (2-1) between positions in each list.
yoff - Y offset (2-1) between positions in each list.
theta - Angle offset (2-1) between positions in each list (degrees).
error - Flag, set if something went wrong in correlating the lists.
This is just a boolean flag. The details of the errors
in the individual frmdxdy. See documentation for frmdxdy.pro
for the internal error codes that you will see on the printed
output.

Keyword Output Parameters

FOM - Figure of merit, a number than can be used (differentially) to
measure how good the spatial correlation is. This number is
approximately the fraction of objects in the shortest list that
ended up spatially correlated. A number close to 1 should be
good.
INDEX- index into list 2 for points in list1, ie, list2[index[i]] is the
closest, or one of a group of closest points, in list 2 to the
ith element of list 1, given the xoff, yoff determined.
SPATIAL- spatial filtering parameters, passed transparently to FRMDXDY.
XOUT - The shifted and rotated X position from the best match.
YOUT - The shifted and rotated X position from the best match.

Common Blocks

Side Effects

Restrictions

It is conventional (and more optimal speedwise) for list 1 to be the shorter
of the two lists. However success is indepenedent of the order in which lists
are presented.

Procedure

Modification History

2007/11/28, Written by Marc W. Buie, Lowell Observatory
2009/07/23, MWB, modified so that x,y input arrays do not have to be
positive definite.
2009/07/24, MWB, added XOUT,YOUT optional output.
2010/02/14, MWB, merged with alternate version from Peter Collins, this
change brings in the INDEX and SPATIAL keywords.
2010/07/19, MWB, cleanup of error reporting output variable
2010/11/30, MWB, fixed busted internal check that made routine never succeed
maxerr keyword not being passed through to frmdxdy, fixed.
2012/12/03, MWB, added pass-through support for SCALEFAC
2016/04/16, MWB, added pass-through support for FNDRAD