Portland Navigation Protraction 250mm Blundell Harling 150000 Locations within this MapGurundu Arnhem Locations within this MapGurundu Arnhem Bay Baralminar River Barrkira Barrkira Landing Ground Burungbirinung River Cape Newbald Cato River Cliffy Point Dhalinybuy Dhalinybuy Landing Ground Everett Island Flinders Point Ganumbali Island Garadandanboi Bay Garalja Island Gikal Gobalpa River Godijboi Point Gonguruwuy Goromuru River Gwakura Island Hardy Island Inglis Island Jandapa Hill Low Island Maiyayigur Point Mallison Island Mata Mata Mata Mata Landing Ground Mudhamul Nalwarung Strait Nyinyiwoi Island Pera Channel Peter John River Probable Island Raymangirr Rekala Island Rhodes Point Rippling Shoal Rorruwuy Rorruwuy Landing Ground Yalliquin Yalliquin Landing Ground Yinyikay Yinyikay Landing Ground Nalwarung Straights Urokona Godjiboi Point Longoidya Low Islet Paperbark Swamp Creek Main Branch Deep Creek Shannons Creek Macleay Hill Chandlers Creek Lanitza Mount Koukandowe Clouds Creek Douglas type square pattern navigational protractor Can also be used as a simple parallel rule and plotter