Re: Control Points/Fiducial Points

From: Bill Sneed (bsneed_at_midcoast.com)
Date: 09/29/04 

Date: Wed, 29 Sep 2004 21:08:42 GMT

"E. Mark Ping" wrote:

> Control points are positioning information sent to a treatment machine
> to deliver radiation.
>
> Jargon may be different in different fields.
>

Interesting...just to confuse matters a bit more...the image
processing software I use for satellite imagery makes the
distinction between "control points" and "tie points"....

Control points are points whose location/elevation are known
from other sources -- a topographic map, a low-level aerial
image, etc....one then tries to co-register the same pixel for
a mountain peak or a road crossing as a "control" point...
then (in some sense) "double checks" the registration via "randomly"
selected "tie" points....

Except when using aerial photography, the term "fiducial"
never enters the process...to make things even worse I have used
old aerial photos with no instrument "fiducial" marks but with
hand-drawn crosses on what the operator/analyst hoped were common
(between photos) points....bill...