▁him , ▁the ▁Is les ▁of ▁the ▁B less ed ▁around ▁the ▁location ▁of ▁the ▁Can ary ▁or ▁Cape ▁Ver de ▁Islands . ▁He ▁used ▁the ▁parallel ▁of ▁Rh odes ▁for ▁measurements ▁of ▁latitude . ▁P to le my ▁mentions ▁several ▁revis ions ▁of ▁Mar inus ' s ▁ge ographical ▁work , ▁which ▁is ▁often ▁dated ▁to ▁  1 1 4 ▁although ▁this ▁is ▁uncertain . ▁Mar inus ▁estimated ▁a ▁length ▁of ▁ 1 8 0 , 0 0 0   stad ia ▁for ▁the ▁equ ator , ▁roughly ▁corresponding ▁to ▁a ▁circum ference ▁of ▁the ▁Earth ▁of ▁ 3 3 , 3 0 0   km , ▁about ▁ 1 7 % ▁less ▁than ▁the ▁actual ▁value . ▁ ▁He ▁also ▁carefully ▁studied ▁the ▁works ▁of ▁his ▁prede cess ors ▁and ▁the ▁di aries ▁of ▁travel ers . ▁His ▁maps ▁were ▁the ▁first ▁in ▁the ▁Roman ▁Empire ▁to ▁show ▁China . ▁He ▁also ▁invent ed ▁equ irect angular ▁projection , ▁which ▁is ▁still ▁used ▁in ▁map ▁creation ▁today . ▁A ▁few ▁of ▁Mar inus ' s ▁opinions ▁are ▁reported ▁by ▁P to le my . ▁Mar inus ▁was ▁of ▁the ▁opinion ▁that ▁the ▁World ▁Ocean ▁was ▁separated ▁into ▁an ▁eastern ▁and ▁a ▁western ▁part ▁by ▁the ▁contin ents ▁of ▁Europe , ▁Asia ▁and ▁Africa . ▁He ▁thought ▁that ▁the ▁inhab ited ▁world ▁stretch ed ▁in ▁latitude ▁from ▁Th ule ▁( N or way ) ▁to ▁Ag is ym ba ▁( around ▁the ▁Trop ic ▁of ▁Cap ric orn ) ▁and ▁in ▁longitude