▁PR S s ▁is ▁not ▁the ▁same . ▁While ▁a ▁D G PS ▁has ▁a ▁high ▁accuracy ▁and ▁precision , ▁a ▁USB L ▁can ▁have ▁a ▁much ▁lower ▁precision . ▁For ▁this ▁reason , ▁the ▁PR S ' s ▁are ▁weight ed . ▁Based ▁on ▁variance ▁a ▁PR S ▁receives ▁a ▁weight ▁between ▁ 0 ▁and ▁ 1 . ▁ ▁Power ▁and ▁prop ulsion ▁systems ▁ ▁To ▁maintain ▁position ▁az im uth ▁thrust ers ▁( elect ric , ▁L - drive ▁or ▁Z - drive ) ▁bow ▁thrust ers , ▁stern ▁thrust ers , ▁water ▁j ets , ▁rud ders ▁and ▁prop ellers ▁are ▁used . ▁D P ▁ships ▁are ▁usually ▁at ▁least ▁partially ▁dies el - elect ric , ▁as ▁this ▁allows ▁a ▁more ▁flexible ▁set - up ▁and ▁is ▁better ▁able ▁to ▁handle ▁the ▁large ▁changes ▁in ▁power ▁demand , ▁typical ▁for ▁D P ▁operations . ▁These ▁fl uct u ations ▁may ▁be ▁suitable ▁for ▁hy brid ▁operation . ▁An ▁L NG - power ed ▁platform ▁supply ▁vessel ▁started ▁operation ▁in ▁ 2 0 1 6 ▁with ▁a ▁ 6 5 3 ▁k Wh / 1 6 0 0   k W ▁battery ▁acting ▁as ▁spin ning ▁reserve ▁during ▁D P 2 , ▁saving ▁ 1 5 - 3 0 % ▁fuel . ▁The ▁ 1 5 4 - meter ▁North ▁Sea ▁Gi ant ▁has ▁combined ▁ 3 ▁power pack s , ▁switch boards ▁and ▁ 2 ▁M Wh ▁batter ies ▁to ▁operate ▁in ▁D P 3 ▁using ▁only ▁one ▁engine