markers silent milestones sentinels pilgrims
markers silent milestones sentinels restored dhawan anmol gpos buried
semaphore milestones sentinels signals relay coded ancient rangan
markers milestones silent sentinels pune stones restored stone distances ht
survey trigonometrical trigonometric everest surveying 1870 trigonometry gts subcontinent indian precision sentinels milestones silent hidden triangles baselines perso metri k2