What historical period does the majority of Irish hydrographic data represent?

The majority of Irish hydrographic data represents the 19th century due to significant advancements in surveying techniques and maritime exploration during that time. This period saw the establishment of rigorous mapping and data collection methods in response to the growing needs of maritime navigation, trade, and safety. The 19th century was marked by the expansion of the British Admiralty’s survey programs, which included extensive hydrographic surveys around the coasts of Ireland. These efforts produced detailed charts and navigational data that formed the foundation for modern maritime navigation.

In contrast, while the 20th century did offer further developments and updates to hydrographic data, the essential groundwork and much of the historical data were laid in the 19th century. The 21st century, being contemporary, would naturally have less than a century of accumulated data relative to the more extensive efforts of the prior century. Additionally, the 17th century, while important in early exploration, lacks the comprehensive hydrographic data that became standard in later centuries. Thus, the emphasis on the 19th century in the context of Irish hydrographic surveys is well justified.