And of course as often happens, I remembered something I wanted to say just as I hit Send... I know of two ways to truly measure from one point to another, both severely restricted. 1)  You can replace the transformation primitives with ones that pass the accumulated transformation down the call tree.  From the bottom of the call tree, you can then have access to both a coordinate from higher in the call tree, and a coordinate from the current place in the call tree.  That is, if you have a module A that calls B and C, you can measure from a point in A to a point in either B or C, but not from a point in B to a point in C.  Ref http://forum.openscad.org/Some-thoughts-on-deriving-world-coordinates-for-objects-td30377.html , which doesn't explicitly provide such a measurement but does *do* such a measurement as part of its demonstration.  (Note the arrow from the label to the orbiting cube; its length had to be calculated.) 2)  You could do all of your geometry "in user space", in arrays of points.  You could then do whatever you want, but you're losing all of OpenSCAD's own geometry processing, except for the final rendering.