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

that were staffed during a session are shown in the figures. Thus, for example, in Figure 6-23 the
first update of Track ID #22637 is the blue square near the center-left of the figure, and the last
update is the green square almost due west of the VT1 site – one of the five sites staffed during
Session 3. The target was confirmed (red square) at 18:54:14 EST by VT1 as the target was
about to pass over the Slocum Road bridge.
Figure 6-23 through Figure 6-32 also help to illustrate both the geometry and consistency of the
Performance Criterion PA4.1 demonstration. For example, Table 6-11 reports site VT1 is 3.3 km
from the radar, while Table 6-12 indicates that the confirmed target T22637 is a little further
from the radar, at 3.6 km. These spatial relationships are apparent in Figure 6-23. Not included
in these tables and figures is the fact that the RFC reported this target as a half mile southwest of
site VT1 – again apparent in Figure 6-23. The visual observer identified the target as a gull,
which is consistent with the speed at which the radar tracked the target (22 m/s), the more or less
straight flight path, and the fact that it is headed north-northeast toward the Neuse River.
In another example, target T64755 was detected 15 times (Table 6-12) but its computed speed
was only 5 m/s. This is consistent with the known behavior of the observed species (Turkey
Vulture) and the fact that the observation was made is an early spring afternoon (1:18 PM), when
the sun is warming the land and creating thermal updrafts that soaring birds follow in tight circles
(i.e., “thermal soaring”) to gain altitude. This behavior is apparent in the close spacing and almost
vertical stacking of the update squares in Figure 6-24. Compare this to another Turkey Vulture,
T44279 that was observed during the early evening (6:54 PM) after the thermals had broken
down: It was tracked at a speed of 21 m/s, covering a distance of 2.5 km.
Conclusion
The observations summarized in Table 6-12 and depicted in Figure 6-23 through Figure 6-32
clearly demonstrate the eBirdRad avian radar system meets Performance Criterion PA4.1: it is
able to detect and track solitary raptor-sized birds at, and in some cases well beyond, the 2 km
radius that would encompass the perimeter of most military airfields.
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