Final answer:
Gerardus Mercator created the flat map known as the Mercator Projection in 1569 to aid sailors in navigation, which has a grid system of latitudes and longitudes and was pivotal during the Age of Exploration.
Step-by-step explanation:
The geographer who created a flat map in 1569 to help sailors navigate long journeys around the globe was Gerardus Mercator. He developed what is now known as the Mercator Projection. This mapping technique improved the ability to chart a course over long distances, helping sailors and navigators of the time. Despite the distortion in the size and shape of continents, particularly as one moves away from the equator, Mercator's map was revolutionary as it introduced a grid system of longitudes and latitudes, which interacted well with other navigational tools like star charts and other celestial observations.
During the 1500s, an era known as the Age of Exploration, maps such as Mercator's played a crucial role. These maps not only reflected the geographical knowledge of the time but also facilitated global trade and travel, influencing the way regions were connected through sea routes.