Home | Marine Aids to Navigation | Onshore Beacons and Towers ALT 1 Onshore Beacons End of Pontoon Usual Application 1 mMax. Height The ALT 1 onshore beacons are mainly used for marking the end of pontoons, supporting a blue marine lantern. The structure is made of polished stainless steel and the height can vary from one to up to 2 metres height. They can support any self-contained lantern. Request moreinformation about ALT 1 Onshore Beacons