 Finally, the total avanzo on the eastward bearing is the avanzar during the deviation (83 miles) plus the avanzo di ritorno (132 miles), thus on the whole, he has covered 83 + 132 = 215 miles on the intended course.Measuring that distance on the map from the starting point ("A"), the mariner can figure out his exact current position.This is the simplest use of the toleta de marteloio.