how to show GPS position in the map

[Karl1]

Hello, I'm still having trouble assigning GPS data to a category.
Phocagallery has that nice map overview when you enter the gallery.
My question: what do I need to do to ensure that the GPS data I entered in the category is actually displayed?

So far, through a lot of "trials and errors", I’ve managed to get the GPS data for an image (which is in a category) to show up in the map overview. But that seems to be completely random—sometimes it works and sometimes it doesn’t.
What is the straightforward solution to this problem?
best regards
Karl1