▁ ▁The ▁geometry ▁for ▁the ▁sky ▁polar ization ▁can ▁be ▁represented ▁by ▁a ▁cel est ial ▁triangle ▁based ▁on ▁the ▁sun , ▁z en ith , ▁and ▁observed ▁pointing ▁( or ▁the ▁point ▁of ▁scatter ing ). ▁ ▁In ▁the ▁model , ▁ γ ▁is ▁the ▁angular ▁distance ▁between ▁the ▁observed ▁pointing ▁and ▁the ▁sun , ▁ Θ s ▁is ▁the ▁solar ▁z en ith ▁distance ▁( 9 0 ° ▁– ▁solar ▁alt itude ), ▁ Θ ▁is ▁the ▁angular ▁distance ▁between ▁the ▁observed ▁pointing ▁and ▁the ▁z en ith ▁( 9 0 ° ▁– ▁observed ▁alt itude ), ▁ Φ ▁is ▁the ▁angle ▁between ▁the ▁z en ith ▁direction ▁and ▁the ▁solar ▁direction ▁at ▁the ▁observed ▁pointing , ▁and ▁ ψ ▁is ▁the ▁angle ▁between ▁the ▁solar ▁direction ▁and ▁the ▁observed ▁pointing ▁at ▁the ▁z en ith . ▁ ▁Thus , ▁the ▁spher ical ▁triangle ▁is ▁defined ▁not ▁only ▁by ▁the ▁three ▁points ▁located ▁at ▁the ▁sun , ▁z en ith , ▁and ▁observed ▁point ▁but ▁by ▁both ▁the ▁three ▁interior ▁angles ▁as ▁well ▁as ▁the ▁three ▁angular ▁distances . ▁In ▁an ▁alt itude - az im uth ▁grid ▁the ▁angular ▁distance ▁between ▁the ▁observed ▁pointing ▁and ▁the ▁sun ▁and ▁the ▁angular ▁distance ▁between ▁the ▁observed ▁pointing ▁and ▁the ▁z en ith ▁change ▁while ▁the ▁angular ▁distance ▁between ▁the ▁sun ▁and ▁the ▁z en ith ▁remains ▁constant ▁at ▁one ▁point ▁in ▁time . ▁ ▁The ▁figure ▁to ▁the ▁left ▁shows ▁the ▁two ▁changing ▁angular ▁distances ▁as ▁mapped ▁onto ▁an ▁alt itude -