ography ▁ ▁In ▁the ▁Middle ▁A ges , ▁Muslim ▁sch ol ars ▁continued ▁and ▁advanced ▁on ▁the ▁map making ▁trad itions ▁of ▁earlier ▁cult ures . ▁Most ▁used ▁P to le my ' s ▁methods ; ▁but ▁they ▁also ▁took ▁advantage ▁of ▁what ▁expl or ers ▁and ▁mer ch ants ▁learned ▁in ▁their ▁travel s ▁across ▁the ▁Muslim ▁world , ▁from ▁Spain ▁to ▁India ▁to ▁Africa , ▁and ▁beyond ▁in ▁trade ▁relationships ▁with ▁China , ▁and ▁Russia . ▁ ▁An ▁important ▁influence ▁in ▁the ▁development ▁of ▁cart ography ▁was ▁the ▁patron age ▁of ▁the ▁Abb as id ▁cal i ph , ▁al - Ma ' mun , ▁who ▁re igned ▁from ▁ 8 1 3 ▁to ▁ 8 3 3 . ▁He ▁commission ed ▁several ▁ge ograph ers ▁to ▁re measure ▁the ▁distance ▁on ▁earth ▁that ▁corresponds ▁to ▁one ▁degree ▁of ▁cel est ial ▁mer id ian . ▁Thus ▁his ▁patron age ▁resulted ▁in ▁the ▁ref in ement ▁of ▁the ▁definition ▁of ▁the ▁mile ▁used ▁by ▁Arab s ▁( m ī l ▁in ▁Arab ic ) ▁in ▁comparison ▁to ▁the ▁stad ion ▁used ▁by ▁Gree ks . ▁These ▁efforts ▁also ▁enabled ▁Muslim s ▁to ▁calculate ▁the ▁circum ference ▁of ▁the ▁earth . ▁Al - M am un ▁also ▁commanded ▁the ▁production ▁of ▁a ▁large ▁map ▁of ▁the ▁world , ▁which ▁has ▁not ▁surv ived , ▁though ▁it ▁is ▁known ▁that ▁its ▁map ▁projection ▁type ▁was ▁based ▁on ▁Mar inus ▁of ▁Ty re ▁rather ▁than ▁P to le my . ▁ ▁Also ▁in ▁the