ABSTRACT
The opacity of water, its variable surface and its reaction to weather all contribute to an environment very different from the land. Hidden dangers, varying navigational depths and the need for safe havens were contributing factors in the establishment of Hydrographic Offices dedicated to the ability to operate naval forces successfully and maintain trade. ‘Safety of Life at Sea’ (SOLAS) remains a principal issue of concern for hydrography. It also sets the context for the widest use of the word and separates it out from hydrology, which covers the properties, distribution and use of water. Nevertheless, the United States maps its surface waters as the National Hydrography Dataset (USGS, 2017) and the European Catchments and RIvers Network System (ECRINS) (Ecrins, 2017) is a fully connected system of watersheds, rivers, lakes, monitoring stations and dams. Oceanographers sometimes use the term ‘hydrographic’ to refer to water quality parameters. An international example (Go-Ship, 2017) describes repeat hydrographic measurements, detailing methodologies for water sampling and analysis, conductivity/temperature/depth (CTD) measurements, and ending with the more conventional interpretation discussed in this chapter.
