As the graphic you've posted shows, the difference between the line from the overpass to the TSBD and one from the overpass to the fence corner is a very small angle, just by cursory inspection. The precise measurement of the angle is kinda beside the point; it doesn't affect the argument one way or the other. It just puts a particular number and unit to a small value. I didn't do so initially because I didn't figure that anyone would require Wopner-at-4:30-grade measurements. In fact, no one else but you seems to have needed them.
The degree of precision isn't arbitrary at all. It's based on the units that people actually use every day when determining and communicating direction where more precise mechanical means aren't available. It stands to reason that these units are determined by the minimum differences in direction that humans can easily discern on their own. One divides a circle into twelve equal sections, the other divides that circle into sixteen. If you wish to differ, that's OK, but you gotta do better than what you've managed so far.
And you still haven't answered my question, since you seem not to like what I use as a benchmark for precision. I'll ask again:
Now, given the real world conditions of Dealey Plaza on Nov 11, 1963, how accurate do you think the TP witnesses audio localization capabilities were at the time?
"In fact, no one else but you seems to have needed them"GeeItsFunToTrollHereJohnny is way out in left field* as usual. He's crackers, Jack. Take hm out to the ballgame and don't forget his peanuts and popcorn. But really, we don't care if he ever gets back.
In that vein, one can point to anywhere in left field and it's still gonna be left field
Take Me Out to the Ballgame
https://en.wikipedia.org/wiki/Take_Me_Out_to_the_Ball_Game#LyricsThanks to Jack Norworth for the 1908 version, which is out of copyright.
My little tale is inspired by his lyrics.
A Modern Tale of How to Strike Out the Side
by Bill Chapman with a great big shout-out to Jack Norworth Before the start of the game (an away game played in Texas against the "Dallas Usual Suspects') the manager of the Little League 'Stepford Sheep Dippers' tells pipsqueak 9 yo left fielder Little Johnny I: "Little Johnny I, notice that the wind is blowing out toward left field today. That includes all of left field, not just the exact spots I'll be pointing at to shift you to"
"But Mr. Chapman", pleads little Johnny I, "my daddy told me that the earth is flat so there can't be any wind.. and that means wind is a hoax and the the government is just pretending."
Manager Chapman replies "Little Johnny I, you're weird." 
* From the Way Out In Left Field Society: "The phrase "way out in left field" has evolved to mean an eccentric, odd, misguided or peculiar statement or act. Although the origin of the phrase has been challenged and debated over the years, the most logical and realistic explanation comes from an extinct baseball park called West Side Grounds that the Chicago Cubs called home from 1893 to 1915. As legend has it, a mental hospital called the Neuropsychiatric Institute was located directly behind the left field wall. The Institute housed mental patients who could be heard making strange and bizarre comments within listening distance of players and fans. Thus, if someone said that you were "way out in left field," the person was questioning your sanity and comparing you with a mental patient"[16][17]
-WikipediaTake Me Out to the Ball Game_1908