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What
is unique about the SeaSonde?
The SeaSonde is the only commercially available current mapping
HF radar with a proven track record. The hardware and software
have all been designed and built by company staff; over 25 years
of evolution has become extremely convenient to operate with
its compact size, operational versatility, complete software
for radar control and data processing. Although many comment
that SeaSonde hardware is striking because it is unusually compact
and robust, believe it or not, 75% of the SeaSonde’s uniqueness
lies in its unseen software. Developing optimized software that
keeps the system running years on end, with nearly no data loss,
has been based on years’ of work till we "got it right".
No one else has anywhere near this track record. This is not
to mention all of the additional software provided at no cost
to make movies, calculate trajectories, do tidal analyses, do
statistical comparisons, etc., etc.
What
else can the SeaSonde measure besides currents?
The most important descriptors of the open-ocean onshore wave
field, i.e., heights, periods, directions, spectral energy density.
In some cases, wind direction estimates. [see advanced question
section for information on how the SeaSonde measures wave descriptors]
How
far out will it measure?
The range of the SeaSonde depends upon a number of environmental
factors (i.e., external noise, significant waveheight, current
speeds), location of radar (such as proximity to water, nearby
obstructions) and SeaSonde operating frequency (the lower the
frequency, the longer the range).
Typical ranges are listed here:
For 4-6 MHz: 160-220 km average during daytime. (With
4-6 MHz only, the range is reduced significantly at night as
external background noise rises.
For 12-14 MHz: 50-70 km
For 24-27 MHz: 30-50 km
For 40-44 MHz: 10-20 km
What
sort of resolution does it have?
The resolution is influenced primarily by the transmitted signal
sweepwidth (or bandwidth). The sweepwidth can be set and easily
changed by the radar operator, but there are tradeoffs with
respect to other factors such as total range and interference.
In addition, the user must normally seek approvals within his
own country for radiated signal bandwidths, and wide bandwidths
at lower HF frequencies are less likely to be approved. Below
are typical range resolution settings:
For 4-6 MHz: 3-12 km
For 12-14 MHz: 2-3 km
For 24-27 MHz: 1-2 km, 24-27 MHz in high-resolution mode:
300 m - 1 km
For 40-44 MHz: 300 m - 1 km
How
many radar stations do I need?
For mapping currents, you need at least two radars looking at
the same patch of water from different angles. The closer the
angle between the two radar bearings is to 90 degrees, the better.
Total current vectors cannot be determined when this angle is
any finer than about 20 degrees, unless you choose to use interpolation
techniques that we make available.
To determine the number of stations required for your application,
first outline your intended observation area. How far offshore
and alongshore does it extend? Choose the frequency of operation
that will allow coverage far enough offshore. Try and space
the radars on shore about 60% of the expected range is. Assume
the radar will view within 10 degrees of the coast unless there
are land or objects blocking the radar view. Consider the subtended
angle issue to make sure that your coverage area has radial
vector production from at least two radars whose angles over
most of the coverage area >20 degrees. Typically users begin
with a network of 2-3 radars, and extend the network over time
to include greater portions of the coast.
Where
does CODAR get the HF radar components it uses for SeaSonde manufacture?
There are no vendors of HF radar components, because HF radars
are only used for the small field of ocean surface mapping.
CODAR staff over a period of 30 years have designed and developed
all of the components used in SeaSonde manufacture. These are
unique, having no commonality with microwave radar components.
Our technology has been proven by years’ experience, and
failure is rare. Because we manufacture all our hardware (as
well as developing all SeaSonde software), "the buck stops
here" because it’s all done here. We will fix it if
it’s broken, rather than passing you on to or blaming a
third party.
What
are the operating costs?
Because the SeaSonde is compact and unobtrusive, it is normally
installed at locations that do not require round-the-clock security
such as the larger phased-array systems from 25 years ago did.
Hence, the sites are unmanned and data are transferred by dial-up
modem or Internet to the desired central location for display
and archiving. Hardware replacement among SeaSonde systems operating
in some cases for over 10 years has been very rare. In other
words, the radar sites have practically no operating costs after
installation except electricity and phone bill. We do, however,
recommend that the radar station computers be upgraded every
few years so they can take advantage of the latest software.
These are inexpensive PC computers that SeaSonde owners can
purchase from computer store.
The SeaSonde is typically configured to operate continuously,
with radial maps, total vector maps, and wave data created every
hour. This is an incredible wealth of information, and as a
network expands to more than a pair of radars, a technician
should be assigned to check basic data flow and quality.
Since
software upgrades were mentioned in your rapidly evolving technology,
how much will they cost?
CODAR policy offers free software upgrades and new software
applications to SeaSonde owners as these become available. In
the past year, not only has all of our software been upgraded,
but three new applications have been developed. These can be
downloaded in compiled form from our website at the customer’s
convenience.
How
much power does a single SeaSonde radar require?
The SeaSonde radar requires less than 1 kilowatt of power. The
radar electronics and computer need to operate within an environmentally
controlled space, which may require air-conditioning. Air conditioning
power requirements usually range between 1-2 kilowatts.
What
are the site preparation requirements?
Here is a basic list of items required at each SeaSonde radar
site. For more detailed instrcutions, see the SeaSonde Users
manual on Site Preparation.
Basic requirements at electronics area:
A. Electrical power:
• Expect power requirements to be approx. 2.5 kW for radar,
computer and A/C
• Power conditioning using Uninterruptable Power Supply
(UPS) units, rated for 1000 volt amps (VA). This UPS should
only be used for the SeaSonde (not air conditioning).
B. Communication lines:
• For transmission of data back to combining station, and
for remotely accessing by CODAR or other local service engineers
when providing necessary customer support. Ideally, this would
be DSL or some other high-speed internet capable connection.
• If a regular phone line is to be used, then it has to
be guaranteed rate BETTER THAN 14.4 kb. The slower the connection,
the less customer support CODAR staff can deliver remotely.
If a connection is less than 14.4 kb, then remote access of
radar for customer support is severely limited.
C. Environmentally-controlled housing for radar electronics
and computer
Basic requirements at Antenna Area:
A. Clear area surrounding RX and TX antennas:
There should be no tall objects/obstructions within speicified
radius of each antenna. Tree trimming/removal, or relocation
of other man made objects may be necessary. There should be
no obstructions between the receive antenna and the seaward
side.
B. Bases/mountings/guy wires for antennas.
There are many options we can recommend for these, depending
on the level of security at the chosen site.
C. Cabling:
• There are 3 RG58 cables connecting the RX antenna to
the electronics, and 1 RG8 cable connecting the TX antenna to
the electronics. Ideally cables between antennas and electronics
are fed through protective conduit (such as 3.5 cm diameter
PVC pipe) and buried in a trench. There are lower cost options
available, but there will be greater risk to exposure and damage.
Why
do I need a quality communication line at radar station even
if I'm not concerned with real-time data?
Two reasons. The overwhelming advantage of SeaSonde ocean remote
sensing is: no instruments in the water to corrode, be damaged,
and fail. Although real-time data may not be important, it is
important not to find after several months operation that something
failed early on, and no data were obtained. A quality communication
line will allow the user to quickly check system operation status
at regular intervals and ensure data integrity and quality.
Second, if a deficiency is suspected, it allows both the user
and CODAR technical staff to diagnose and often repair it, without
ever needing to visit the site. CODAR staff do not charge for
such modem diagnosis and support, even after the first year
warranty period, if such access is available.
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