Yes that is the proper namespace needed.
xmlns:epub="http://www.idpf.org/2007/ops"
but you seem to be using epub2 pieces here (ie an NCX) and not epub3 NAV. A fixed layout epub support was not added until epub3. And epub3 uses a html NAV not an NCX (although an NCX doc could be added for epub2 backwards compatibility) but probably should not use epub:type attributes which are from epub3 for that same reason.
For example here is what might appear at the top of a NAV:
Code:
<?xml version="1.0" encoding="utf-8"?>
<!DOCTYPE html>
<html xmlns="http://www.w3.org/1999/xhtml" xmlns:epub="http://www.idpf.org/2007/ops" lang="en" xml:lang="en">