Oswald in the doorway: the blog of the Oswald Innocence Campaign, by Ralph Cinque

This graphic shows Altgens' position. It's a little ahead of the walkway. He was pretty much directly across from Zapruder. 

So, if we crop off the bottom of that image of Dealey Plaza, we get this:

Getting the position exactly right is not the issue. It makes no difference. The point is that Altgens had no problem visualizing both areas. It is ludicrous to think that someone who was in front of the monument would manifest east of the Depository entrance.