Final answer:
Before computers, mapmakers used various techniques to create map projections, including the widely-used Mercator projection. They relied on observations from explorers and knowledge from other sources to create maps of the known world.
Step-by-step explanation:
Before the advent of computers and geographic information system (GIS) software, mapmakers created map projections using various techniques. One notable map projection developed in 1569 by Gerardus Mercator is still widely used today. Mercator maps display a grid overlay of horizontal and vertical lines showing longitude and latitude on a flat earth, but they distort geography as one travels further from the equator. Mapmakers also relied on observations from explorers, such as Christopher Columbus, and knowledge disseminated by others to create maps of the known world.