Matsayin kowane ma'ana a kan farfajiyar za a iya bayyana ta hanyar haɗin gwiwar biyu: latitude da longitude. Ba kamar haɗin gwiwar Cartesian na jirgin ba, bambancin haɗin kai ba daidai yake da nisa a farfajiyar ba, kamar yadda aka nuna a zane a hannun dama: ga wani a kan mahaɗin, motsi 30 digiri na longitude yamma (magenta line) daidai yake da nesa na kimanin kilomita 3,300 (2,100 mi), yayin da ga wani a latitude na 55 digiri, motsi 30 digiri na longitude yamma (blue line) ya rufe nesa na kimanin kilomita 1,900 (1,200 mi). Coats ba su da isasshen bayani don bayyana geometry na farfajiyar, ko kuma mafi mahimmanci na kowane nau'i na geometric ko sararin samaniya ko sararin samaniya. Wannan ya riga ya bayyana yadda za a iya bayyana kowane nau'i na sararin samaniya da sararin samaniya daidai da nisa, kamar yadda aka bayyana a cikin wani nau'i na sararin samaniya ko sararin samaniya da aka ambata a baya, wanda ake kira Riemann, yana amfani da wani nau'i na geometric wanda aka kwatanta ta hanyar da ma'auni na sararin samaniya
ƙwallon ƙafa