TELEFOS:

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TELEFOS A new surface drifter for coastal and
lake studies
V. Zervakis1, M. Ktistakis2, D. Georgopoulos1 and
A. Kantidakis2
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TELEFOS the concept
The idea of designing and building TELEFOS was
generated at the Hellenic National Centre for
Marine Research, when it was realized that almost
the entirety of the Aegean Sea is by now fully
covered by cellular telephony
Coverage by the three main companies
VODAFON
COSMOTE
TELESTET
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• The initial idea
• NCMR researchers realized that cellular telephony
  (GSM) could be significantly more advantageous
  than satellite or UHF tracking of the floats, in
  terms of
• Communication cost
• Real-time access to the information
• Flexibility to monitor the floats from anywhere
• Flexibility to reprogram the floats for easier
  retrieval.
• Based on that idea, we started looking for
  partners to build a surface drifter specially
  designed for the Greek Seas.
• The Consortium
• A manufacturing company with great experience in
  manufacturing navigational equipment, MARAC
  Electronics, was interested, and a common project
  started under the auspices (and 50 funded) by
  the General Secretariat for Research and
  Technology of the Hellenic Republic.

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The new drifter Through our interactive work, we
believe that we have come up with a new drifter
that is characterized by the following novelties

• GSM communication (with option for ARGOS)
• Short-range communication (and programming)
  through UHF (no hussling with connectors)
• Novel design, allowing the very easy conversion
  from measuring surface currents (Davis type) to
  subsurface currents (kite down to 50 m depth).
• Low-cost accessories (alkaline batteries)
• A user-friendly, highly capable software

As the real-time data acquisition will permit the
easy tracking and retrieval of the drifters, the
instruments will acquire a semi-expendable
character. This lowers the real cost of the
initial investment.
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The Hardware
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Characteristics

• Hull constructed of PVC
• Weight lt 5Kgs (float only)
• Hull 90cm X 15cm
• Sail area 1m2

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TELEFOS is designed to measure both surface and
subsurface currents In surface mode, the design
is based on the Davis type. In subsurface mode,
the inner body of the drifter is turned into the
surface buoy, and the hollow outer body forms the
spine of the kite.
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One of TELEFOS novelties lies in the design The
modification of a drifter from the surface mode
to subsurface mode takes place in a couple of
minutes
Surface mode
Subsurface mode
Simply pulling the float off the kite
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The Software
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As Telefos is targeted to a wider market than
marine scientists, the software is designed from
the start to be as user-friendly and
comprehensive as possible. Selecting the
geographic area is a click away.
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• The software is comprised of
• the project scheduling/drifter programming mode
• The real-time drifter monitoring mode, and
• The data analysis mode.

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• project scheduling/drifter programming mode
• the user sets
• Region and length of the experiment
• Number and identification of drifters to be used
• Sampling rate (GPS interrogation)
• Reporting rate (GSM calling home)
• real-time drifter monitoring mode
• the user can
• Observe his/her drifters in real time (and know
  their positions)
• Change the reporting rate to facilitate drifter
  chase and recovery

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The data analysis mode A more extensive
presentation of the data analysis mode follows.
We should just point out that the analysis can be
performed not just on TELEFOS data but also on
any Lagrangian drifter data, surface or
subsurface.

• The graphical interface provides a user-friendly
  way to filter out bad data.
• The following computations are possible with the
  data analysis module
• Lagrangian velocities, accelerations and Rossby
  numbers (along the path of the drifters)
• Eulerian statistics (Velocity fields)
• Lagrangian statistics (integral time scales, eddy
  diffusivities)
• Semi-Lagrangian Spectra

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Example with borrowed data-set from WOCE drifters
in the Aegean Sea Each drifter can be identified
by a different color, determined interactively.
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Simply moving and letting the mouse over a
drifter position, a box appears

• showing
• the drifters code
• date and time
• Position
• estimated speed
• estimated direction
• Rossby number
• surface temperature
• (for the WOCE drifters TELEFOS are not yet
  equipped with thermistors)

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Using the zoom button, we can focus in an area
to view details of the tracks
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Removing bad data, either by deleting single
points or by selecting a group of points, is done
easily with the mouse.
The details of single points to be erased are
shown in inset boxes.
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The Lagrangian velocity is estimated just by
clicking to the folder velocity
and leaving the option grid unchecked
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Checking the option grid, we obtain Eulerian
means over a grid laid on the region of interest
Moving the mouse over the center of a grid point,
we see its statistics.
The size of the grid is controlled by a
slide-ruler
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The variance ellipse is displayed by clicking to
the folder confidence
A slide-ruler controls the desired confidence
interval
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There is also a folder option providing the mean
kinetic energy
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and one for the eddy, or fluctuating kinetic
energy
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These autocorrelation functions are the first
step in estimating integral time scales and
horizontal diffusivities. The work is under
progress.
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• Conclusions
• Telefos will constitute a low-cost, very
  versatile instrument.
• Telefos novelties improve its cost-efficiency,
  while facilitating its use.
• We seek to expand the market to non-marine
  scientists by offering ease of use and
  user-friendly data analysis.
• The first prototypes have been built the first
  four instruments will be delivered to NCMR for
  sea trials in January 2003, and six more
  (production-type) will be ready until the summer
  2003.
• Additional Information Vassilis Zervakis (NCMR),
  at zervakis_at_ncmr.gr
• 
  Antonis Kantidakis (MARAC) at kantidakis_at_marac.gr

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• What is TELEFOS?
• TELEFOS is a state of the art system for
  measuring currents and calculating dispersion
  (e.g. pollutants) in the near surface waters. Its
  concept is based on a new design on an old idea,
  i.e. of using drifters to monitor the circulation
  in aquatic bodies.
• The system consists of a monitoring station
  (which may be placed either on land or aboard the
  deployment/retrieval vessel), and the drifter
  fleet. The drifters positioning exploits the
  highly accurate GPS system.
• The main innovations that TELEFOS brings are
• Use of GSM and RF technology for communication.
• A modular design allowing two configurations,
  thus enabling the monitoring of surface and
  subsurface currents (down to 50 m).
• A potent, user-friendly software offering
  real-time monitoring and interactive programming
  during the mission, a vessel-guiding module for
  the retrieval of the drifters, and extensive data
  analysis features (assessment of mean and eddy
  velocity and kinetic energy fields, lagrangian
  statistics, horizontal diffusion coefficients,
  spectral analysis).
• The software allows the import and analysis of
  any drifter data.

MARAC ELECTRONICS and the HELLENIC CENTRE FOR
MARINE RESEARCH present a new surface drifter
(Telephonic monitored drifters for ecological
studies - TELEFOS), designed for use in
semi-enclosed seas, coastal areas and lakes.
Monitoring surface currents
Area selection tool

• APPLICATIONS
• Environmental impact studies
• Port construction
• Sewage dispersion from point sources
• Aquacultures
• Experimental validation of numerical simulations
  of circulation
• Calibration of coastal HF current/wave radars

Monitoring sub-surface currents
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• POSITIONING
• GPS
• COMMUNICATION
• ISM433
• GSM
• DIMENSIONS
• Weight lt 5Kgs
• Hull 90cm X 15cm
• Drogue surface 1m2
• OPERATIONAL LIMITS
• -5oC to 50oC Air Temperature
• -2oC to 45oC Water Temperature

Vessel-guidance module
Lagrangian Statistics decorrelation scales
www.marac.gr - www.hcmr.gr