On Apr 17, 10:54*pm, "Steve B" wrote:
I need one of those pen contraptions that you roll over blueprints and
aerial photos that then give a numerical value to the distance traveled.
What are they called, and what's a good supplier of them?

Steve

Heart surgery pending?www.cabgbypasssurgery.com
Heart Surgery Survival Guide

I think these are what you want. :-)
http://www.geodetic.com.au/category607_1.htm