Agar ba rui khariga va globus nigarem, dar on khathoero mebinem, ki az SHimol ba Janub va az Garb ba SHarq tul kashida, yakdigarro buridaand. Onhoro dar sathi Zamin baroi muayyan kardani koordinati (arz va tuli) obekthoi geografi istifoda mebarand. Ba in maqsad meridiani asosy (ki qutbi SHimoli va Janubiro …

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