What Does a Hydrographic Surveyor Do?

Surveying Under the Seaand return to the electronic device for notation.
Despite the cartoon image of a deep-sea diverBy blanketing the bottom of a body of water
peering through a surveyor's transit, with airwith sound waves, it is possible to create an
bubbles rising all around, the ability to accuratelyincredibly accurate picture of what lies below.
survey underwater topography is extremelyBathymetrics
important. Hydrographic surveyors are used toThe term bathymetry is also used to describe
identify all sorts of underwater features andhydrographic surveying. In addition to determining
objects. Energy exploration firms employ them tothe depth of water at any given point, plus
help find oil and gas deposits. The shipping industryproviding a picture of the bottom, GPS data are
uses them to make sure that channels are freeused to fix each exact sonar return to a specific
of dangerous obstacles, whether natural orpoint on the globe. This process allows surveyors
man-made. Treasure hunters hire them to mapto tie in land-based monuments with their
out the location of sunken wrecks, andover-water equivalents, helping engineers and
environmental agencies need them to keep trackother end-users of this information understand
of erosion.exactly where a particular peak, valley, rift or
Always in Motionunderwater piling rests on a map. Bathymetric and
Wherever there is moving water-oceans, rivers,hydrographic surveying is usually conducted
streams or tide-affected lakes-there isaboard some sort of watercraft. Depending upon
movement beneath the waves as well. Thethe body of water under examination, this could
hydrographic surveyor is called upon to createbe a sea-going vessel, a smaller craft such as a
underwater maps of a lake- or seabed, and totugboat, or even an inflatable device like a Zodiac.
mark the navigable portions of rivers. TheseThere are even hydrographic surveyors who use
maps must be updated regularly because of thatunderwater vehicles, but these are generally
movement. Silt builds up to clog harbors, andemployed for picture taking since GPS signals
storms can cause massive shifts in thecannot penetrate the water's surface. Lacking the
topography below the water line.ability to collect GPS data, it is difficult to
Hardware of the Hydrographic Surveyordetermine an exact x/y point on water through
Naturally, the surveyor does not go underwatersome lesser function.
to achieve his goals. However, the most primitiveUsing Software to Perfect Hydrographic Surveys
tool at the disposal of a hydrographic surveyor isData collected under one of several
nothing more than a rock at the end of a string.processes-sonar is standard, but some companies
Measure the depth of a channel by dunking thehave employed LiDAR (Light Detection and
rock into the water; note the place where theRanging) in shallower areas-is post-processed and
water's surface strikes the string when the rockthen used to create something called a digital
hits bottom; finally, measure the distanceterrain model. This is similar in method to what is
between the rock and the string marking oncedone for land features, except that elevation
you hoist the rock out of the water. Note thereadings are replaced by depth readings. A
location on a hand-drawn map and repeat-oh,number of factors can affect the viability of data,
perhaps a million times or so. Naturally there is aincluding the motion of the collection platform
better way to do this. Sonar, the same device(boat), tides, and even water temperature. Once
that helps surface ships locate enemy submarines,corrections have been made, many software
is highly useful for mapping the bottom of a bodyprograms have the ability to directly create maps
of water. Sound waves are generated andand charts to show what has been collected
directed straight down. They then bounce offbeneath the waves.
something, whether the bottom or an obstacle,