Ed In Australia the code (AS3500) requires the vent to terminate
1. 600mm above any opening into the building.
2. 150 mm above the point of penetration through any roof.
3. 3m above any trafficable roof
4. 2m above or 600mm below any chimney or similar opening within 3m from the vent.
4. 5m from any air duct intake.
5. 600mm above any eave, coping or parapet that is within 600mm horizontally from the vent.
These distances are what the Standard calls for, however when inversion occurs common sense should prevail & the vent should terminate at apoint where it does not offend, if practical.