Norwegian to English Tech/Engineering Construction / Civil Engineering architectural lines

As it's written in the text, incl. any errors: Aksen i kirken går nord-sør og i denne asken ligger det Otta skifer med naturplan. Fra inngangen beveger mann seg mot lyset via en sluse hvor Jerusalemkorset er felt ned i Ottaskifer.
Advice appreciated - is it an axis or are they talking about the cross-shape of the nave and the horizontal part by the alter (not sure what that's called)? Guess I didn't expect all this to turn up in a document about the use of natural stone...