introduction of the ocean radar · 1. introduction wera is a shore based remote sensing system...

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Introduction of the Ocean Radar

Features and Accuracy

Thomas Helzel & Anna Dzvonkovskaya

Victoria, B.C., 12th of June 2017

WERA antenna array on public beach Range resolved Doppler spectrum Current map at US east coast


1. Introduction of WERA

2. Compact or Array Type Antenna

3. Unique WERA Features

4. Applications

5. Conclusions

Contents


1. Introduction

WERA is a shore based remote sensing system using the

over the horizon radar technology to monitor ocean surface

currents, waves and wind direction. A vertical polarised

electromagnetic wave is coupled to the conductive ocean

surface and will follow the curvature of the earth.

The rough ocean surface

interacts with the radio wave

and due to the Bragg Effect

back-scattered signals can

be detected from ranges of

more than 200 km.


1. Introduction, WERA

The back-scattered radar signal will be Doppler shifted

with a specific frequency offset given by the velocity of the

gravity wave that is responsible for the Bragg scattering.

These Doppler shifted

signals will be symmetrical

around the centre frequency

as long as the ocean surface

does not move. An ocean

current will shift these

Bragg lines up or down in

frequency.


Beam formed spectrum of one pixel (1 x 1 km) 30 km offshore

(27 MHz, 16 channel WERA system)

1. Introduction, WERA


1.1 Introduction - Currents

Current map:

new data all 12 min

spatial resolution: 1.5 km

fo = 12.4 MHz

2 x 16 antenna arrays





4. Applications

5. Conclusions

Contents


2.1 Compact or Array Type Antenna System

Features and Limitations of Compact or Array Type

Radar Configuration

One of WERA’s unique features is that it is flexible to be set-up in Compact or Array Type configuration.

This allows us to discuss the pros and cons of these

configurations full and frank with potential radar users

and enables us to find the best radar configuration for

your specific application !



Parameter Compact Antenna

(Direction Finding)

Array Type Antenna

(Beam Forming)

Receive Antenna Array:

Provided Data:

Field of View:

Angular Accuracy:

Temporal Resolution:

Noise Reduction:

Square of 4 Poles

Currents and

Wind direction

up to 270°

< 10° typical

Antenna calibration

recommended !

> 20 minutes

standard

8 to 16 Poles

Dynamic Currents,

Waves and Wind

120° (more if curved)

< 1°

Antenna calibration

not required !

> 30 seconds

unique WERA noise

reduction method



Current map:

Port Area Rotterdam,

The Netherlands

Integration time: 9 min

spatial resolution 1 km

fo = 16.15 MHz

2 x 12 antenna arrays



Current map:

12 antenna

arrays, BF

Current map:

8 antenna

arrays, BF

Current map:

4 antenna

compact, DF



Current map:

12 antenna

arrays, BF

Current map:

8 antenna

arrays, BF Current map:

4 antenna

compact, DF


Curved Rx array

Long Range WERA

(8.3 MHz)

East Australia

near Gladstone.

Tx array

2.4 Small Antennas


Active Loop antenna

11.2 MHz, height 1.5 m Active antenna

12.3 MHz height 1.2m

9.3 MHz Rx antenna

height: 2 m

2.5 Very Small & Active Antennas





4. Applications

5. Conclusions

Contents


3. Introduction of Unique System Concept

• The non-interrupted FM-cw technique in combination

with the software beam forming, is the guarantor of

WERAs outstanding performance and reliability.

• The rf low noise generation performance of this technique

allows to operate multiple WERA stations sharing the

radio band without disturbing other radio band and users.

• Software Beam Forming makes WERA the fasted and

most flexible ocean radar and it offers the unique

self calibration feature.


3.1 FM-cw versus FM-i-cw

Figure taken from:

M. Heron, “ HF Radar Optimized for Tsunami Monitoring”, Proceedings of IEEE Oceans

Geneva 2015

Radar range for 1st order

Bragg signal versus radar

frequency, for 10 WERA®

systems with 12 and 16

antennas, blue line, and for

10 SeaSonde ® systems,

green line.

Data based on 12 months

statistics of 10 systems of each

kind installed in the US and

additional systems sourced form

the Australian ACORN network.

This is why WERA uses the non interrupted FM-cw technique,

The better S/N performance results in more range, so a higher frequency

can be used to get the required range resulting in better performance.


3.2 Range of WERA Products (Technique)

1. For Direction Finding or Beam Forming Mode

2. For Short or Long Ranges

3. In Standard, Compact or Splitted Site Geometry


3.03 Site Geometry Options

The Standard Site Geometry requires a separation of the Rx and Tx

antenna arrays by about 5 to 10 wavelengths

(25 to 150 m, depending on operating frequency)

The Curved Site Geometry provides a wider angular field of view.

The Arbitrary Spaced Site Geometry allows to adapt the antenna

position to environmental conditions (e.g. at the edge of a cliff or

attached to a fence along a foot path).

The Tx array is very compact and can be placed on the roof of the

equipment container or a beach hut.

The Compact Site Geometry requires no separation of the Rx and Tx

antenna arrays but will provide a reduced operating range. Any

compromise between the normal and the compact geometry is possible.

The Splitted Array Site Geometry requires no cable connection

between the Rx and Tx antenna arrays. The Rx and Tx stations can be

connected wireless over a distance of up to 3 % of the radar range.






4. Optimised Integration Time for individual applications


The unique, parallel and phase conserving signal

processing of the WERA system, to apply software Beam

Forming to provide data from entire range within short

integration time:

3.04 Features of Unique System Concept

2 min in 30 s steps for ship tracking or disaster warning

5 min for current mapping

20 min for wave data on the grid


Tsunami signature with an integration time of

9 min (left)

3.04 Time-Sensitive Applications

The used software beam forming method provides

highest accuracy in near real-time. This is very important for

time-sensitive applications.

or 2 min (right)


3.04 Time-Sensitive Applications







6. Supports Multiple Input – Multiple Output Mode, MIMO

5. Intelligent Frequency Management to avoid interferences


3.06 MIMO Reduces the Array Length

Tx1 Tx2 Rx1 to Rx4 with /2 separation

with 4 /2 separation results in a synthetic 8 antenna array

Using two Tx antennas

separated by the length of the receive array plus /2

would double the effective length of the receive array.







8. In Single- or Multi-Frequency Mode

9. Self organized Frequency Band Sharing

6. Supports Multiple Input – Multiple Output Mode, MIMO

5. Intelligent Frequency Management to avoid interferences

7. Provides very effective radio interference suppression, RFI

10. Open Data Interfaces for scientific applications


The WERA data processing structure is optimised to carry out a very

efficient noise reduction and software beam forming algorithms in near

real-time.

3.10 Open Data Interfaces

Met-Ocean &

other

application

software

Standard Users

Noise

reduction and

Beam

Forming

(or DF)

Ship Tracking

Tsunami Warning

Data Pre-

Processing

and data

volume

reduction

Scientists

WERA

Hard- &

firmware

Output for:

Experiments


3.3 Range of WERA Products (Applications)

11. Ocean current maps with Highest Temporal Resolution

12. Various Wave data options available

13. Maps of Significant Wave Height

14. Directional Wave Spectra for individual gird cells

18. Ship Detection & Tracking including multi sensor tracker

20. Near shore Current Vector Maps from single WERA station

16. Ocean Current Forecasting for vessel traffic services

15. Drift Prediction for Search and Rescue operations

17. Tsunami Detection & Probability check in near real time

19. Automatic Identification of Eddy Currents


3.20 Near Shore Coverage

With a 12 or 16 antenna system it is possible to derive current vectors

from a single station. This can be used to get current vectors in the near

shore area without overlapping coverage from two stations.


3.20 Near Shore Coverage

Comparison of u- and v-component, measured with two stations in red

and derived from a single station in blue (sample from 7 km off-shore).


3.4 Range of WERA Products (Quality)

21. Certified Quality Management implemented since 2001

22. System in EMI tested by independent authorized laboratory

23. Highest data availability of > 95 % (certified by customer)


Customer reported Data Availability

within 40 km range

(Data from SHOM, France)

Raw data availability: 98.6 %

Availability of near real-time data: 87.1%

permanent since January 2007

The near real-time availability was lower because of data link problems

(ADSL connection failed due to strong lightning).

Near real-time holes were filled by reprocessing the raw data.

3.23 Reliability


3.4 Range of WERA Products (Quality)

21. Certified Quality Management implemented since 2001

22. System in EMI tested by independent authorized laboratory

23. Highest data availability of > 95 % (certified by customer)

24. All released Software Validated by WERA Partners

28. Remote Controlled, via web interface from PC or smart

phone 29. Robust System operates even with some defective antennas

26. Antenna Systems are automatically tested once per hour

25. WERA hardware with integrated Self Test Functions

27. Beam Forming with Self Calibration Function

30. Safe Operation, no dangerous voltage at Tx antennas


3.5 Range of WERA Products (Data)

31. Professional Data Management software

33. Quality and Plausibility Check of all data in near-real time

34. Easy generation of Animated Maps

35. Access to data of Individual Grid Cells with one mouse click

39. Warning, if oceanographic parameter reaches defined value

40. Option to Integrate External Sensor Data into maps

37. Generation of Time Series for individual grid cells

36. Access to Archived Data

38. Simple Export Options for all data and maps

32. Display of Data Maps in near-real time





4. Applications

5. Conclusions

Contents


Simulation of a Search and

Rescue case. The prediction

of the actual position of a

drifting buoy “man-over-

board” was compared with different trajectory methods.

WERA based trajectories

showed the best accuracy.

Data are kindly provided by Actimar.

Drift prediction using

WERA current data around

Ushant

4.1 Application: Current Drift Prediction


Drift prediction using WERA current data around Ushant

4.1 Application: Current Drift Prediction

Drift prediction

based on

hydrodynamic

model data

Drift prediction

based on

WERA data


Data kindly supplied by Actimar and

SHOM from their WERA system

Map with Wave Height and Direction Directional spectra

wind direction

4.2 Wave Data of Individual Grid Cells


Directional spectra


4.3 Application: Mobile WERA

• WERA is compact and easy to install.

• Cables and antennae are light weight and easy to handle.

All material (cables and

antennas) fit into a

trailer which is used as

equipment container for

a WERA System.





4. Applications

5. Conclusions

Contents


5.1 Conclusions

The shore based radar system WERA is a powerful

oceanographic instrument giving reliable information

about large ocean areas.

The outstanding temporal resolution makes WERA

a perfect component for time critical applications like

disaster warning systems and ship tracking.

Very small antennas and the MIMO technique allows to

get best performance with compact antenna systems

It is easy to install and flexible for various application.


5.2 Conclusions

HELZEL provides a virtual server for placing data to be

shared and to install & run experimental software

To support the scientific group working on Tsunami

Detection by means of WERA, we suggest to install a

working group for “Tsunami Alerting with WERA”

• Group members arrange local meetings (seminars) to

attract potential users of that region.

• HELZEL supports such meetings (sponsoring)

• The Group arranges Skype conferences

• The Group meets occasionally at conferences


Acknowledgement

We would like to thank:

Lynn K. Shay (RSMAS) providing their WERA data from the Florida coast,

SHOM and Actimar for providing data from SURLITOP project,

Dana Savidge (SKIO) and George Voulgaris (USC) for providing the data sets

from their long range systems,

RWS, The Netherlands, for providing the data from Rotterdam area,

Klaus-Werner Gurgel (Uni Hamburg) and his team for continuous support of the

WERA projects.


Thank you for your attention !

Since 1999, more than 100 WERA systems are installed.

Permanent WERA Installation

Temporary WERA Installation

Planned WERA Installation

introduction of the ocean radar · 1. introduction wera is a shore based remote sensing system...

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