Interactive Geometric Reseau Location

?	print this menu
q	exit, saving the new positions
b	Back to the original input positions
a	Assign X,Y position to a reseau mark, replacing INDEF
d	Delete the nearest reseau mark
p	move one Point, without affecting others
o	specify One reseau mark and the new location, then shift
t	specify Two reseau marks and their new locations, then transform
f	specify Four reseau marks and their new locations, then transform
r	Replot all the points
s	Save the current reseau positions
u	Undo the changes since the last "s"
l	Lock onto the reseau by moving to minimum pixel in search area

The parameters are listed or set with the following commands which may be
abbreviated.  To list the value of a parameter type the command alone.
:show			List parameters
:xsearch	i	x side of box used to search for min pixel
:ysearch	i	y side of box used to search for min pixel
:x1 		r	Alter viewport lower x
:x2 		r	Alter viewport upper x
:y1 		r	Alter viewport lower y
:y2 		r	Alter viewport upper y