OBSERVATIONAL VALIDATION OF AVIAN RADAR SYSTEMS

Wendell BunchEdwin Herricks, PhD

Introduction

• Existing airport surveillance radars– Designed for air and ground traffic control– Not readily adaptable for wildlife purposes

• Avian radar systems– Digital processing added to COTS marine radar

and optimized for bird detection – X-band and S-band– New technology w/few users and no airport

experience

CEAT Performance Assessment

• Multiple year program assessing avian radar systems at civil airports

• Initial efforts intended to understand radar physics/system abilities

• A critical issue is validation of capabilities of avian target detection and tracking

• Visual observation of birds

CEAT Validation Efforts

• Address ground-truth issues• Validate in airport settings• Use target rich environment of Whidbey

Island to conduct long term observations• Coordinate with IVAR efforts• Evaluate methods

• Issues identified in ground-truth efforts and validation studies

– observers challenge radar detection– radars challenge observers and methods– visualizing the beam coverage (height and width)– locating specific targets– judging distance and altitude

Location: NAS Whidbey Island WA

Primary sensor X-band radar 3cm wave length

Method of visual observation– 30X spotting scope aligned to true north– radar computer and watch synced ± 1 sec– data collected in high and low clutter areas– viewing angles separated by 20 degrees– two view samples at each angle, high/low– 20 second sample periods– data collected: date/time, family or specie, number of

birds, general direction of travel, bearing target observed– time stamp when target on vertical center of spotting

scope

Findings• Detection Issues:

• Aspect/RCS• Aspect -relation of the target to radar beam• RCS - effective target area, changes with aspect• RCS must exceed level of clutter

Clutter: Ground and Sea Undesirable radar returns Sea clutter – tracks short high speed Wind speed/direction determined effect

Ground and Sea Clutter

Effects of sea clutter on tracking

Detection Issues: cont.• Position Relative to Clutter

– gulls: >20, <20, <5– Large sea ducks: CEAT and IVAR– RCS?

• Flight Behavior– constant heading = consistent tracking– un-predictable flight challenges all radar– shadowing in flocks

• Duration of Flight– must be long enough

Detection Issues: cont.

• Weather– rain/snow hinders detection and tracking– can generate large numbers of detections and tracks– tracks of short duration with speeds similar to birds

Observation Issues

• weather conditions hindered use of spotting scope in strong winds/rain

• range to targets difficult to estimate• limited to daylight hours

Validation Methods

• Requirements to validate target time, direction of travel, bearing, within beam dimensions for the bearing

• archived radar data replayed • two examples

Surf scoter - 305

Bonaparte’s Gull - 601

Conclusions

– Avian radar capable of tracking bird sized targets– Researchers have shown radar can track

movement over larger areas than visual observations

– Research needed: potential to monitor bird activities while evaluating limitations of location and radar physics

– NAS Whidbey research has shown limitations with the current technology

Conclusion cont.

• Factors Compromising Detection– target aspect– target size– flight behavior– target position relative to clutter– overall clutter environment– weather

Conclusions cont.

• Use of Avian Radar Systems– careful evaluation of clutter levels to ensure tracking in desired area– will require some level of validation– more complex environments = more validation

QUESTIONS?