the european age of discovery during the 16th and the 17th centuries, where many new lands were discovered and accounts by european explorers such as christopher columbus, marco polo, and james cook revived a desire for both accurate geographic detail, and more solid theoretical foundations in europe. the problem facing both explorers and geographers was finding the latitude and longitude of a geographic location. the problem of latitude was solved long ago but that of longitude remained; agreeing on what zero meridian should be was only part of the problem. it was left to john harrison to solve it by inventing the chronometer h-4 in 1760, and later in 1884 for the international meridian conference to adopt by convention the greenwich meridian as zero meridian.