I have sold open channel flowmeters since 1975. We even sold the DataGator when it originally came out. Why would you not mention the most popular meters that measure both area and velocity for Q. Larry Marsh invented this idea more than 30 years ago, and it has been copied by everyone since. The latest version is a complete non-contact Flo Dar. Check out Hachflow.com. I think your article ("Flow Like an Egyptian," Aug '12) was one page short.
[Walt Boyes replies: You are correct, I omitted the area/velocity flowmeters from the discussion, and I should have included them. Attached to the online version is a PDF presentation based on my article, and an additional item that includes that topic.]