az im uth ▁grid ▁( with ▁alt itude ▁located ▁on ▁the ▁x - axis ▁and ▁az im uth ▁located ▁on ▁the ▁y - axis ). ▁ ▁The ▁top ▁plot ▁represents ▁the ▁changing ▁angular ▁distance ▁between ▁the ▁observed ▁pointing ▁and ▁the ▁sun , ▁which ▁is ▁opposite ▁to ▁the ▁interior ▁angle ▁located ▁at ▁the ▁z en ith ▁( or ▁the ▁scatter ing ▁angle ). ▁ ▁When ▁the ▁sun ▁is ▁located ▁at ▁the ▁z en ith ▁this ▁distance ▁is ▁greatest ▁along ▁the ▁horizon ▁at ▁every ▁cardinal ▁direction . ▁It ▁then ▁decre ases ▁with ▁rising ▁alt itude ▁moving ▁closer ▁toward ▁the ▁z en ith . ▁ ▁At ▁tw il ight ▁the ▁sun ▁is ▁setting ▁in ▁the ▁west . ▁Hence ▁the ▁distance ▁is ▁greatest ▁when ▁looking ▁directly ▁away ▁from ▁the ▁sun ▁along ▁the ▁horizon ▁in ▁the ▁east , ▁and ▁lowest ▁along ▁the ▁horizon ▁in ▁the ▁west . ▁ ▁The ▁bottom ▁plot ▁in ▁the ▁figure ▁to ▁the ▁left ▁represents ▁the ▁angular ▁distance ▁from ▁the ▁observed ▁pointing ▁to ▁the ▁z en ith , ▁which ▁is ▁opposite ▁to ▁the ▁interior ▁angle ▁located ▁at ▁the ▁sun . ▁Un like ▁the ▁distance ▁between ▁the ▁observed ▁pointing ▁and ▁the ▁sun , ▁this ▁is ▁independent ▁of ▁az im uth , ▁i . e . ▁cardinal ▁direction . ▁ ▁It ▁is ▁simply ▁greatest ▁along ▁the ▁horizon ▁at ▁low ▁alt itudes ▁and ▁decre ases ▁linear ly ▁with ▁rising ▁alt itude . ▁ ▁The ▁figure ▁to ▁the ▁right ▁represents ▁the ▁three ▁angular ▁distances . ▁The ▁left ▁one ▁represents ▁the ▁angle ▁at ▁the ▁observed ▁pointing ▁between ▁the ▁z en