Angle of Elevation

A couple of years ago, in my first game as a brand new umpire in a one-man (no base umpires) system, I made the first real self-correction of my umpiring career.  On a ball hit to the infield, I would trail the batter-runner down the line to make the call at first.  I did that a few times, and saw I really wasn't getting a good look.  So I started moving out closer to the pitcher's mound, and saw a great improvement.  I didn't realize it at the time, but I pretty much had taught myself the "angle over distance" philosophy that experienced umps already knew.

Not much is written about the one-man system, even though this is where most rookie umpires will start out, at least in my area.  In all the literature about two-man systems and up, the plate umpire is expected to trail the batter-runner (BR) up the line in fair territory to assist the base umpire on a call where there's the possibility of a swipe tag or the first baseman's foot coming off the bag.  The angle is good for either of those calls, but not too good on a safe/out call.  The photo on the left shows a view from that perspective.  It's going to be pretty hard to see the runner's foot touch the bag.  Instead, when I move closer to the mound, I can get a better angle, shown in the photo on the right.

So, what makes the best angle in this situation?  Draw a line from a point halfway up the third base line straight to first base.  I try to position myself as close to that line as possible, and secondarily as close to 1B as possible, as long as I give myself time to stop and set.