08/07/2026
Comprehensive Guide to Hydrographic
Surveying
Hydrography is the science of measuring and describing the topographical
features and the entire aquatic environment as a whole, beneath the
surface of water bodies. These subsurface features affect bridge scour,
flood mitigation, erosion control and siltation transport, maritime
navigation, marine construction, dredging, offshore oil exploration and
offshore oil drilling, among many other activities.
Hydrographic surveying does not strictly apply to coastal and oceanic
regions of the US. Hydrographic surveying has many applications inland.
Many environmental and civil engineering project in and around bodies
and channels of water (streams and rivers, lakes and ponds, wetlands) can
all benefit from hydrographic surveys and analysis.
Topics
Intro and overview of hydrographic surveying
History and early methods of measurement
Sounding poles, lead lines, wire drags
Echo sounders and fathometers
Agencies which perform hydrographic surveys: office of coast
survey, NOAA, USGS, COE, IHO, NOO
Marine magnetometry
DC resistivity imaging
Radar altimetry
GPR for marine applications
SONAR devices: side scan, single beam, multi beam sonar
Light Pulse (LIDAR) devices
US maritime limits and boundaries
Sources of existing bathymetric datasets
Types of tidal datums (sounding and chart) and tidal cycles
AUV, ROV and UAS technologies
Crowdsourced bathymetric surveying
Fisheries acoustics
Bathymetry
The term "bathymetry," originally
nautical in origin, referred to the
ocean's depth relative to the sea
level (free surface), although it
has since come to refer to the
“submarine topography,” or the
depths and shapes of the
underwater earthen terrain.
Hydrography is a branch of physical oceanography
or applied science which deals with the measuring
and description of the configuration of the bottoms
and adjacent land areas of oceans, lakes, rivers,
harbors, and other water forms.
What are Hydrographic Surveys?
A hydrographic survey deals with measuring and
description of features of a water area and the bed
configuration; however, it may also encompass a
wide variety of other objectives such as the
measuring of tides, currents, gravity, Earth
magnetism, and for determining the physical and
chemical properties of water.
Bathymetric Surveying
The label of hydrographic surveying is often
synonymously applied to bathymetric surveying.
However, the
latter actually
refers to the
study and
measurement of
the bottom or
“bed” of a
navigable water
body (whether it
is an ocean, river,
lake or other body or channel of water.) In other
words it deals with the topography of the solid
earth, beneath a body of water.
Below are various types of hydrographic surveying
methods.
Hydrographic Surveys for Safe Navigation
There are numerous reasons to conduct a
hydrographic survey, but the most common
objective is for compiling nautical data along
navigational channels, with an emphasis on the
measurement and profiling of the subsurface
physical features that may affect safe navigation
and travel by marine vessels.
The image above shows a dredging operation
consisting of a clamshell bucket dredge on a barge
Documenting the Geomorphic Changes
Routine hydrographic surveys are essential to
documenting the transportation of silt and
sedimentation, in order to unsure safe lanes of
shipping in rivers and along coastlines.
Natural currents and storm events such as
hurricanes tends to shift the silt on the sea or river
beds, potentially accumulating in previously
dredged channels, causing dangerous conditions or
obstructions.
Locating Submerged Obstacles
In addition to the surveying of geomorphic
changes, hydrographic surveys may be utilized to
locate submerged vessels and other hazardous
debris along river and sea beds.
A hydrographic survey can be used to facilitate
offshore oil and gas exploration, drilling operations,
marine construction, dredging, installation of
subsea cables and more.
Other Applications
Other applications for hydrographic surveying:
to generate the data needed to create and
update nautical charts
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