Hydrography; What is it?

If you’ve read the About the Author Section, then you know that I claim to be a hydrographer, but I’ve recently had a few exchanges that led me to realize that not too many people know what hydrography is; someone was asking about hydrography as it pertains to hydrology (a hydrograph is a graph showing the rate of flow (discharge) versus time past a specific point in a river, or other channel or conduit carrying flow), and I wanted to make it clear that hydrographers are people too.  I thought I might take a few blog posts to explain the origins of hydrography and its importance to the safety of navigation on the water.
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Hydrography is a field of study involving the determination of water depth and other physical oceanographic properties (tide, currents, waves, etc.), for the purposes of navigation. Essentially, modern hydrographers use sonar (multi-beam and side-scan) to determine water depth and produce nautical charts for navigation.

The earliest hydrographers used sounding poles to measure the water depth (as seen above, there are hieroglyphs from ancient Egypt that depict this practice), and until WWII the primary method for conducting a hydrographic survey was lead line (a lead weight on the end of a length of line to measure water depth) and wire drag (a wire dragged between two vessels at a set depth to clear an area to that depth or snag obstructions for further investigation and least depth determination). In the 1940s echosounders, or single-beam sonars, came into wide use for survey work. Not until fairly recently, 1990s, have full bottom insonfication methods become the standard for a hydrographic survey. Multi-beam and Side Scan Sonar are now the standard methods used to conduct a hydrographic survey. Once data is collected and processed by hydrographers, it is passed on to cartographers who compose the actual charts.

Hydrography predates Oceanography, and that field of study is actually an outgrowth of hydrography. Oceanography as a field is now commonly thought to include Hydrography as a specialized field dealing with physical oceanography information as it pertains to safe navigation.

In the US, NOAA’s Office of Coast Survey has been conducting hydrographic survey work and producing nautical charts for US waters since 1807 (The Survey of the Coast was the US’s first scientific agency). Other countries have similar offices that are responsible for producing nautical charts in their territorial waters (United Kingdom Hydrographic Office is one of the oldest; established in 1795). Member hydrographic offices are governed by the International Hydrographic Organization that sets international standards.

​The National Society of Professional Surveyors in the US, offers a certification in Hydrography in conjunction with The Hydrographic Society of America (THSOA), which is why I could call myself a certified hydrographer, though that certification has now lapsed.

That’s a short thumb-nail sketch of hydrography as a field of study and in future installments I will go into detail about how it is conducted and what that might mean to the safety of your navigation; hopefully that will be of interest.  Until next time, here’s wishing you fair winds and following seas.