654 leagues West of Seville. Because Seville is well north of Cape Verde, the meridians are clustered closer together at Seville's latitude than at Cape Verde's latitude. A ship sailing west of Seville will, in fact, reach the real Tordesillas meridian (point T on map) well before 654 leagues are sailed (point D). The rule of marteloio has sailors plot routes by drawing plane triangles on a chart, as if the world's surface were flat. While this might be practical enough for sailing confined to the compact latitudes of the Mediterranean Sea, it is quite misleading on a grander scale. Relation to later rules Relation to the "regiment of the leagues" In the late 15th and 16th centuries, the improvement of nautical astronomy and the introduction of latitude parallels allowed navigators to determine their position at sea by celestial readings, rather than relying on estimation of distance sailed. The successor of the rule of marteloio was the "Regiment of the Leagues" (regimento das léguas), that was used by Portuguese navigators sailing in the Atlantic Ocean. Or, to use the term introduced by William Bourne (1571), the "Rule to Raise or Lay a Degree", also known as the "Table of Leagues" or the "Rule for Raising the Pole". It was first written down in the Portuguese navigation manual Regimento do astrolabio e do quadrante (published in Lisbon c. 1509, but written c. 1480) It was popularized by Martín Cortés de Albacar in his 1551 Breve compendio la esfera y del arte de navegar. The "Regiment of the Leagues" is not very different from the rule of marteloio. The Regiment of the Leagues always considers the west-east bearing as the "intended course" and measures set deviations from it. More specifically, the league table considers a fixed value of alargar – set at 1 latitude degree (or, in the measurements of the time, 17.5 (Portuguese) leagues, or equivalently 70 (Italian) miles). It then gives for every different quarter wind of sailing direction (always designated as quarters away from the north-south axis, rather than away from the intended course), the relevar and the afastar. The relevar is the number of leagues on the actual course that a ship must sail in order to cover the pre-set 1 degree of latitude (17.5 leagues of alargar from the starting parallel). The afastar is merely the corresponding avanzar on the west-east bearing. Example: Suppose a ship sets