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CODAR Ocean Sensors, Ltd.
Announces its
Fall 2005 Session
HF Radar Training Course:
CODAR Ocean Sensors Fall Training Course will be held at the Seymour Discovery
Center (UC Santa Cruz’s Long Marine Laboratory).
Tuesday 1 November at 9:30AM
through Friday 4 November at 3:00PM
Course Fee:
Tuition is USD $750 per person, and includes course materials, 4 lunches, two
dinners. New SeaSonde owners should contact Company for priority reservations.
Training Schedule:
A DRAFT schedule is
available here for download (Word document - 24K).
Software sessions will focus on SeaSondeRadialSuite_10 and SeaSondeCombineSuite_10
(Mac OS X).
Course Reservations and Payment:
Registration Form
(PDF 20K) is provided here for download. Please fill-in and FAX to +1 (408) 773-0514,
or send an e-mail containing the same information to:
Registration and payment must be received by October 1st. Payments can be made
via check (U.S. only) written to CODAR Ocean Sensors, Visa credit card, or issuance
of a Purchase Order from your institution.
Mail check to: CODAR Ocean Sensors, 1914 Plymouth Street,
Mountain View, CA 94043 USA, Attn: TRAINING COURSE. If paying by credit card,
please fill in Credit Card Authorization section at bottom of Registration
form and FAX to:
+1 (408) 773-0514.
For more information on
Group Lodging & Driving Directions,
Please CLICK HERE
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Long
Marine Lab - Seymour Center
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Class
instruction during
Spring 2005 Training Course |
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Course attendees
Spring 2005 Training Course |
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Are
you up to date?
SeaSonde10 users should
be running:
SeaSondeRadialSuite10 Release 3 with Updater3 installed.
SeaSondeCombineSuite10 Release 3 with Updater3 installed.
Mac OSX 10.3.9 (Jaguar) or 10.4.2 (Tiger)
Third Party Software:
Timbuktu 7.0.4 (required for latest Timbuktu scripting).
Timbuktu 8.1.1 is currently undergoing testing for compatibility.
OS9 SeaSonde users should be running:
SeaSonde 4.4f6
Mac OS 9.2.2
NOTE: SeaSonde10 Release4 is scheduled for release November 1,
2005.
The following features are specifically in Release 4:
• Wave Model Method data output for multiple user-specified range cells.
• Default file output is now LLUV (Latitude/Longitude positions with u
and v components) for radials and totals. The LLUV files contain much more meta
data of the settings used, the tool versions, and diagnostic info over the radial’s
coverage time.
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•
LLUV radials now contain more quality
factors: Temporal, Spatial, maximum velocity,
and minimum velocity. Only the Temporal
or Spatial is available to the older
radial output.
• Enhanced LLUV and SeaDisplay grid and vector positioning from use of
the great circle calculation.
• New Transponder controller in SeaSondeController should make it much
easier to setup the receiver and the transponder for antenna pattern measurements.
• SeaSondeAcquisition raw cross spectra files are now named with the standard
spectra date stamping so that they can be easily archived.
• New utility SpectraScrambler that can unscramble cross spectra that were
generated with swapped antenna channels.
ECO Updates (Engineering Change Orders):
ECO_050601_TR_chip_replacement - This change order is only for users experiencing
firmware lockups of the AWG and or T/R modules that produce a loss of transmitted
power and require site visits to cycle power to the receiver hardware.
The D4 chip replaces the older D2/D3 chips and is user installable. This
chip upgrade is NOT recommended if you are not experiencing these problems.
Contact COS for additional information. (link to details/ECO document). |
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Waves from the
SeaSonde
Background: Currents
are mapped based on scatter from waves.
So why isn't getting wave information even
simpler, i.e., like the first step? The
answer is: these dominant echoes that contain
current information come from short, not-very-high
ocean waves that are not all that interesting.
True wave information comes from a weaker,
more complicated part of the echo spectrum,
called second order. Barrick (of CODAR)
was the first to derive the model relationship
that explained this echo 35 years ago.
Lipa (of CODAR) was the first to use this
model to "invert" the echo and
get wave information nearly 30 years ago.
She and Barrick did this first for HF radars
with big phased array antenna systems,
and later for SeaSonde-type radars with
compact antennas. During the interim, we
have been working on making wave extraction
robust and meaningful (as have others).
We're there! It's taken a long time, hasn't
it? But then, it's "second order",
and that's more complicated.
A Quick Lesson on Waves:
Waves in deep water are statistically the
same over a large distance (called fetch)
and for a long time period (called duration).
For example, 3-m high waves (significant
waveheight) change very little over fetch
distances of 150 km and time durations of
10 hours. At particular locations for short
periods of time, their random nature can
cause much larger (or smaller) waves to appear
briefly and then die just as quickly. But
these "rogue waves" cannot be observed
by any HF radar. The radar can only obtain
statistical averages over an area several
kilometers on a side. Hence, it doesn't make
a lot of sense to "map" waves in
deep water over distances of ~40 km (the
maximum for wave monitoring from second order
echo with affordable HF radars). The interesting "sea-state
waves" just don't change over these
scales, like currrents do.
Waves do begin to change statistically when any of three things happen. (1) They
move into shallow water near shore; (2) They diffract around a headland or are
funneled through offshore islands; (3) They encounter strong current shears.
For example, the 3-m high wave with period 10 seconds and wavelength 140 m will
begin to change when the depth is less than about 30 m. Its direction changes
(it comes in more perpendicular to shore), its speed changes (it slows down),
and its wavelength shortens; its temporal period (10 s) always remains the same.
The bathymetric impacts will transform the deep-water non-varying offshore wavefield,
causing it to vary with position along the coast. And, it really is the waves
coming onto the coast that everyone wants to know -- these are the ones that
do the damage.
What the SeaSonde Measures: With the above in mind, SeaSonde
wave algorithms were created to measure the onshore deep-water wave spectral
parameters, of which waveheight, period, and direction are the simplest and most
important descriptors. Our algorithms right now assume the measurements take
place in deep water. We've found these to be adequate perhaps 95% of the time.
We will soon have versions that account for shallow water. But remember, they
still find the deep-water wavefield, the part that doesn't change with position.
It was these waves that produced the near-shore variations along the coast in
the first place. However, these variations are obtainable from the same shallow-water
refraction/dispersion relations used in our inversion algorithms. Therefore,
you will have "mapped" the wavefield to positions along the coast by
starting with the non-varying deep-water wavefield. SeaSonde wave parameters
are outputted typically every 10 minutes, but then are usually averaged over
an hour to reduce the natural random statistical
fluctuations, as is done with wavebuoys.
Limitations: There are limitations to ours or any HF radar's
ability to measure waves that must be disclosed. (1) Radars that operate at higher
frequencies (e.g., 25 MHz) cannot measure high wave conditions (e.g., greater
than 4-m significant waveheights). The theoretical model needed for the algorithm
doesn't permit it. (2) Strong currents across the radar cells will limit wave
information obtainable. This also becomes worse at high radar frequencies (e.g.,
a 2 knot current at 25 MHz will not allow observations of waves whose periods
are greater than 8 seconds). (3) On the other hand, although low radar frequencies
(5 MHz) can extract any waveheight under any current conditions, the second-order
spectral echo is weaker and more prone to be buried by noise or interference.
For the SeaSonde, this means robust and continuous wave measurement pretty much
ceases when waveheight is less than 1 m at 5 MHz, but is super for higher wave
conditions. With these disclosures, what's left still encompasses an awful lot
of the coastal wave climatology of interest. All the while, you are mapping currents
with your SeaSondes. And, you don't have anything in the water to get fouled
or lost! It's the only "non-contact" coastal wave monitoring system
that has proven its salt over many years' operations and tens of radar locations.
And finally, you didn't pay anything extra for a wave software package
-- it
comes free with your SeaSonde!
Setup Specifics: CODAR staff want to help you set up your software
for your coastal radar location, at least the first or second time. First of
all, based on the frequency band of your radar, we will look at: (1) the depth
offshore; (2) the maximum expected current flows close to shore. We can then
advise you whether
and when wave measurements may be meaningful.
Secondly, we can help determine the required parameters for your set-up files
(Preferences). These include: (1) angles subtended by the local coastline; (2)
which range cell(s) to use for wave processing; (3) noise threshold; (4) parameters
that help find the boundaries between first and second order echo -- the former
used for currents and the latter for waves. And then we will monitor your system
performance for waves during the subsequent weeks to help fine-tune these parameters. |
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Tech's Corner:
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Wave Processing in Multiple Range Cells
Simultaneously!!
-- New With SeaSonde10Release4 --
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A 12Mhz SeaSonde is ideal for a
high wave environment
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What's New With SeaSonde Wave Processing:
SeaSonde10Release4 software provides two wave algorithms for estimating wave
parameters from sea echo. The Wave Model method has undergone a number of refinements
this year and we are very excited about the quality and close agreement of data
from SeaSondes with corroborative data available from nearby wave buoys. This
algorithm processes each CSS file into a wave measurement point . The wave height,
period, wind and wave direction parameters are stored as individual lines of
text in a monthly summary WVLM* (ASCII) files. The text files can be plotted
with WaveDisplay or easily imported into users’ custom scripts.
The alternative algorithm is Wave Spectral and uses a spectral inversion approach
for estimating wave parameters. This algorithm processes CSA (hourly averaged
CSS) files into hourly wave measurements which are then stored as individual
lines of text in a monthly summary WVLS* (ASCII) file. Hourly Wave*.wv4 spectral
files are also produced. The spectral files contain period, spectral energy and
direction for each of the frequencies sampled. This algorithm does not support
multiple range cell processing. Follow the links below for additional details
about Tsunami wave detection and wave measurements with SeaSondes.
http://www.codaros.com/images/about/2005Lipa_Tsunami.pdf and
http://www.codaros.com/images/about/2005Lipa_Nyden_wave.pdf
New Features in WaveDisplay:
Simultaneous plots of measurements in multiple range cells are now possible with
our latest version of WaveDisplay. This provides an invaluable check for wave
measurement consistency from range cell to range cell (note wave height trends
in the plot below). The “Multiple Ranges” checkbox found in the “Radial
History Adjuster” window activates this new feature. Checking this box
allows you to plot a single “Wave Model” parameter for up to three
of the selectable range cells using the tabs in the window. If WaveDisplay is
set as a “Startup Item” at your radial site a real-time plot will
be displayed and updated with each CSS processed. A jpeg or png image is also
created automatically and stored in the directory /Codar/SeaSonde/Data/Pictures/Latest/WaveFitModel.jpg.
This
is a ready-to-use graphic that can be posted to the user’s web site.
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Wave Parameters in Up to Three Range Cells Can Be Plotted at Once
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Can't Wait?: CODAR staff want to help you set up your software at least for
the first time. But if you're the type that can't wait to try out our new tools
and would like to turn on wave processing just to have a look, here's the "Easy
Install" method. The method and settings below are appropriate for many
(but not all) SeaSonde installations. If the default software settings below
produce unexpected results (or no results at all) please contact us.
Steps for Turning on Wave Processing:
First have a look at: (1) the depth offshore; (2) and the maximum expected
current flows close to shore. Then decide if your site has the appropriate
wave environment to process waves (based on Barrick’s recommendations
in the preceding article).
Configuring the Software:
Two important parameters must be set manually* in the header.txt file (located
in the RadialConfigs folder) using a text editor. Line #15, Parameters 3 & 4
("factor down peak nulls" & "wave noise factor" should
be set to 10 & 3 respectively. The maximum number of range cells for wave
processing is set with "parameter 1" in Line #14 of header.txt. If
you put in "5", you will get wave measurements in range cells 1-5
provided that you have second order peaks in your CSS files out to range cell
5. If no second order peaks are present then no data should be produced. Second
order peaks are rarely detectable beyond range cell 5 so this is a good starting
point for first-time setups.
The coastline coverage bearings can be set using the RadialSiteSetup utility
(/Codar/SeaSonde/Apps/RadialTools/RadialSiteSetup). We recommend that you stick
this icon in your computer's dock for quick and easy adjustments to wave and
current processing parameters. As you face out to sea measure the true north
(unobstructed) bearing to your right and to your left. If you have a compass,
you can use the program MagneticDeclination to convert to true north. Alternatively,
you can estimate True North bearings using SeaDisplay in conjunction with your
site file. The total span must be at least 160 degrees and less than 200 degrees.
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Configuring Wave Processing With RadialSiteSetup
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If your site is a 5Mhz Seasonde located on an offshore platform or a small
island that may have waves coming from behind the SeaSonde, then the "allow
long range waves to be offshore" box needs to be checked. The coast
angles can then be set with no limit to the span.
The "Use inner Bragg sidebands for waves" should be left unchecked
unless advised otherwise by CODAR staff.
Lastly, check the appropriate box to activate "Wave Model" processing
(best option) and/or "Wave Spectral" processing. Relaunch the SeaSonde
processing software and note the comments in the Terminal window as the processing
tools are run. Report any errors or problems to our support staff. On first
startup it may take up to 30 minutes for the "WaveModelForFive" file
(for Wave Model Processing) and/or the "WaveForFive" (for Wave Spectral
Processing). This only occurs the first time the new wave parameters are run.
If the wave parameters are changed the initial startup will repeat this step
to create updated WaveForFive and WaveModelForFive files.
Need Help? If you need assistance evaluating your preliminary data or if your
software is not performing as expected, please email us or call 408-773-8240, Ext. 24. We're here to help and will be more than happy
to help you fine-tune your wave processing parameters.
*The new version of SpectraPlotterMap utility in Release4 also provides an
interactive method to set first order (currents) and second order (wave) parameters. |
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Help is Available if You Ask
CODAR has a dedicated and experienced Support team available to help customers
with potential problems, and can provide instant feedback if you suspect something
is not right with your data.
Examples of situations that might precipitate contacting our support staff: (1)
Significant variations in maximum coverage, e.g., radial map patterns fluctuate
by 40% over a 24 hour period. (2) Noticeable, regular gap regions appear in specific
positions on your maps. (3) Wild vectors occasionally are spotted in circular
bands at ranges from one or the other site from 100-130 km (for Long-Range systems).
Any change from data outputs that you had been getting, or from what you expected,
can probably be remedied ... But we need to know what you are seeing that you
don't like! We will then swing into action, diagnose your problem, fix it, and
educate you as to what happened.
At the lower operating frequency bands, late-afternoon and nighttime radio interference
is known to occur, even in systems that had not been seeing this before. Nighttime
is when radio broadcasters use the lower HF band, and usually for only a few
hours. Such interference appears as noise to our processor. Maximum range will
decrease during these periods, even though vectors closer in are perfectly valid.
Remedies are to shift positions within your present authorized frequency band,
or move to another frequency that you were granted. We can diagnose this immediately,
and teach you how to do it also.
PLEASE NOTIFY US OF ANY PLANNED CHANGES BEFORE OR WHEN YOU
MAKE THEM
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Often a customer will change frequency
bands, move one of the antennas, or rotate
the receive antenna, perhaps for a very good reason.
We can often advise you before such a change what kind of "domino effect" this
could result in. Also, immediately after the change, we can monitor your system
to verify that it is operating correctly, or make recommendations for additional
modifications. Again, we will keep you informed as to what we find. Nearly 85%
of problems happen as a result of a change to system settings (software or hardware)
that we are unaware of. We only want your systems to be producing the best possible
data for you. When that happens, we both look good. But we can only do that with
input from you.
Don't hold back!
If you have any questions,
please email us |
1914 Plymouth Street
Mountain View, CA 94043 USA
Phone: +1 (408) 773-8240
Fax: +1 (408) 773-0514
www.codaros.com |
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