society > travel > aspects of travel > guidance in travel > [noun] > that which guides or leads > milestone or post > mark from which distance measured (2)
zero mark1821
(a) a mark on a scale or instrument from which a positive or negative quantity is reckoned; (b) a mark from which distances along roads or…
zero post1908
a post from which distances along roads or railway lines are measured; cf. zero markn.