(IVAR) - Final Report - Strategic Environmental Research and ...

3.1.1.1.1 Tracks Single Birds and Flocks [PA1.1]
We established Performance Criteria PA1.2 (Automates Real-Time Tracking of Radar Echoes)
and PA2.2 (Provides Reduced Clutter Compared to Analog Radar) to demonstrate that the
Accipiter® digital radar processor used in the eBirdRad avian radar systems can:
• Faithfully reproduce digitally the same images, including the echoes from moving targets
that an observer would see on the analog radar display.
• Through the suppression of ground clutter, expose echoes from moving targets that were
not visible on the analog display.
• Automatically detect the echoes of moving targets and identify from scan-to-scan those
echoes belonging to particular targets and combined the appropriate echoes into target
tracks, all in step with the radar's scan rate of 2.5 seconds/scan (here nominally referred
to as "real time"; Section 2.4.1).
• Record detailed data about the position and behavior of the targets being tracked.
The three sets of tests conducted as part of Performance Criterion PA1.1 were designed to: 1)
Visually confirm that targets being automatically tracked by the radar were birds, either
individuals or flocks of birds; 2) Use thermal imaging as a second method of confirming that
targets being automatically tracked by the radar were birds; and 3) Track a remotely controlled
aerial vehicle for independent verification the accuracy of the spatial and temporal coordinates
being generated by the radar. We set as our success criterion for this objective that we would be
able to confirm 100 or more targets tracked by the radar at three different geographic locations.
The first of these tests, Validation by Visual Confirmation, involved deploying teams of trained
birders at various distances and bearings from the radar, at different geographic locations, and
during different seasons and times of the day, and asking these teams to “ground-truth” the
targets that were being tracked by the radar. Using two-way radios for communications, either
the radar operator asked the visual teams to confirm a target the radar was tracking was a bird or
the visual teams first saw a bird they thought was in the radar beam and asked the radar operator
for confirmation.
The visual confirmation studies, while very labor-intensive and time-consuming, were
undertaken because no published studies were available that had used quantitative and objective
methods to confirm the targets digital avian radars were tracking were in fact birds – a most basic
assumption underlying the use of this technology.
The second set of tests, Validation by Thermal Confirmation, addressed the same objective –
confirming the tracked targets are birds – by using the infrared (thermal) portion of the
electromagnetic spectrum to observe birds being tracked by the digital avian radar system.
Thermal imaging has the additional benefit that it works at night, while visual observations can
only be made during daylight.
The device used to makes these observations employs a thermal imaging video camera pointed
vertically to detect the heat signatures of the birds (and bats and insects) as they pass overhead,
together with a vertically-pointed radar that recorded the height of these targets. The IVAR team
positioned this system at different distances from the avian radar and correlated the tracks of the
targets observed by both systems.
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