It is my understanding (could be wrong of course) that the addition of ところ to a verb draws the time aspect of the verb nearer to the speaker/subject. So the following progression can be established.
I walked there (Unclear about the time except that the action is over and done with.)
I just walked there (States that the action ended very recently from the perspective of the speaker/subject.)
I am walking there (States that the action is currently occurring)
I am about to walk there (States that the action hasn't happened but will in the near future.)
I will walk there (States that the action hasn't happened and will in the future.)
I have read that 歩いているところだ can also be translated as "I am walking".
Could someone please explain how 歩いている (when it implies continuing action as opposed to habitual action) differs in meaning from 歩いているところだ and how it could be placed in the above progression if possible? In addition, I feel like it may be a separate issue so please ignore if too complicated, when would 歩いていたところだ be used?
If I had to guess, I'd say that 歩いているところだ falls between 歩き始める and 歩いている.
As a slight side note, for momentary verbs, does 帰っているところ mean "I am just about to enter the house" or "I am just about to leave where I am and start going home"?