wow... this is very complex
That's precisely why I didn't want have include additional fields automatically into the search in the first place. But I see no other way.
-the additional fields is only for search?
Yes, at least for now.
easy variant
1) images screen: selection by addtional fields
2) edit screen: edit gmap latitude or longitude... (the same as date or keywords, description)
1) your request is pretty much specific, which might be only useful for you alone or for that specific fields. Because there are many ways using additional fields, there are many different ways search in them, and one way might not work for all of the fields.
your way is not exactly understandable
Maybe a little confusing because you probably haven't seen such method in 4images, but in other softwares such method is pretty common.
The reason why I decided add a checkbox to each field is because that's the only way to determine if user wanted search images with an empty string in the additional fields or they didn't want use additional fields at all.
So, now you'll need activate each individual field if you want include it into your search.
If that is too confusing then I probably should not even think about improving search functionality by adding "functions" dropdown menu to each search field like in phpmyadmin