I dunno, BigInch, using my own, God-spec foot (and compensating for the difference between mine and the distance between some guy's nose and the tip of his outstretched hand) works well for me.
Seriously though, laser scanning has many advantages, one of them being objectivity - assuming that the setup laser guys are well-trained. You end up with a "data cloud" (think connect-the-dots) which can be imported into various 3D CAD piping programs. Very nice, but relatively expensive at the outset.
Remember that the quality of field measurement often depends on the crew's experience and the ambient weather. Frozen fingers don't hold a plumb bob or tape measure very well.
Good laser pointers, paintball guns and many photos from different angles might be an on-the-cheap solution.
I think Disto is one manufacturer of laser measuring devices. Just make sure your measurement guy is a knowledgeable piper or you might end up with dimensions to something irrelevant:
Measure Guy: "Look, I followed all the manufacturer's instructions, twice, just to make sure!"
Field Guy: "Then why is the tie-point 6 5/16" off?
Measure Guy: "I dunno, I made sure I was lined-up X-Y and put the laser spot on the 'pipe' wall."
Field Guy: "Was the laser spot on something shiny?"
Measure Guy: "Umm, maybe. But I'm SURE it was the pipey thing I was supposed to shoot."