@Tom Dunlap if the measurements are used for consulting I want the tape to be capable of holding its own on the liability spectrum. Metal does not stretch as much over time and the dbh tapes don't have an expiry that I'm aware of. Not calculating dbh from circumference takes away a real or potential source for error - human, online calculator, hand calculator, etc. A factory issue, unaltered tape transfers liability straight from the tree to the data management system without the potential for questions to be asked, unless they are asked of the tape manufacturer.
I find that depends on the trees I'm measuring. If they are all relatively close in diameter, I'll get really good at that. I did some inventory work on southern pine plantations. By the end of a day I was within 1/4" on every tree (we were measuring to 0.10). Now, when I'm marking timber in mixed hardwoods, I'll tally trees 14"-44" (on rare occasion bigger...) and everything in between (2" diameter class). When you are all over the board like that 24" and 26" start to look real similar...especially because 24.9" is tallied as 24" and 25.1" is tallied as 26".Anyone who does a lot D measurements will start making side bets with themselves to guess the D then measure. One person I met who did trunk injections got so good they didn't need to measure. Like any skill that took some kinda practice. They did measure and record when it was important. For injecting the accuracy of using the right volume of product is key not one or two more or less injectors.
Who provided the sizes?