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Fugro Pelagos is a world leader in providing reliable and
innovative solutions to the offshore oil and gas industry,
which include a variety of tasks from high-precision rig positioning
for oil exploration, to delivering preliminary seismic survey
data, and pipeline inspections. The company operates in all
the major offshore exploration areas with over 30 locations
worldwide.
One of the areas in which Fugro Pelagos has been undertaking
marine operations, is off the coast of Alaska, from northwest
of the Aleutian Islands to as far east as Glacier Bay. The
operations vary from hydrographic surveys to tidal studies,
and for various organizations interested in fish harvesting
and offshore exploration. Despite having access to the latest
motion sensor marine technology, the company was having difficulty
maintaining heave accuracy in the unpredictable sea conditions
along the Alaskan Coast. Doug Lockhart explains, "The
marine survey environment is extremely challenging. Long period
waves with continuously variable swells in both period and
amplitude can play havoc with just about any motion sensor."
Hydrographic Surveying
"TrueHeave effectively improved our error
budget from IHO Order 1 to IHO Special Order"
Fugro quickly saw the solution. By implementing Applanix
TrueHeave technology with their existing POS MV system, they
could very effectively improve their heave precision, with
the added bonus of reducing heave artifacts at the same time.
TrueHeave is based on an advanced processing algorithm, which
uses both past and present vertical motion data, to compute
a significantly improved heave estimate. The POS MV has sufficient
computational speed to utilize a two-sided filter, which allows
a secondary estimate of heave to be generated shortly after
the sonar acquisition event.
The new system with TrueHeave installed was used operationally
for the first time in 2003, when the company undertook a hydrographic
survey for the National Oceanic and Atmospheric Administration
(NOAA). Describing the results Doug Lockhart said, "In
analyzing the data profiles we could immediately see an improvement
in heave accuracy of about 20cm, which was substantial. We
effectively improved the error budget from IHO Order 1 to
IHO Special Order, an impressive feat given the sea state
at the time of the survey."
In addition to improving the quality of their data, Fugro
were able to take advantage of the reduction in heave artefacts
generated with the new system. This allowed for a significant
reduction in time and operational expense. TrueHeave dramatically
reduces filter settling time as compared to a traditional
heave filter, which almost completely eliminates the need
for line run-ins. This means a saving of several minutes per
survey line, which can translate into a saving of hours or
even days worth of labor and vessel costs.
