for each post get category (custom taxonomy page)

i have categories assigned to each author. this files their posts
and allows me to call their description and avatar on a category listing page for them, as a header.

the real indexing is in the 4 custom taxonomies, such as location, type, etc.

when someone selects a location, like north-east, it goes to the taxonomy template list page (taxonomy-location-north-east.php) that
includes posts from multiple authors.

I need to have a list of all of the Categories (Authors) that get returned with posts in that (location) custom taxonomy.

a query of all posts that match that location, and then getting their respective categories or authors, i think, would work … but i don’t know how to do that.

is there an easier way? is there no way to call get_the_category for a lists of posts?

thanks in advance.