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

Figure 2-2. Configuration of BirdRad system.
A useful feature of the FR-2155BB, and another reason for choosing this particular model, is the
user-selectable “True Trails” display. In this mode, the radar displays returns from the current
scan in yellow; it displays returns from the previous 15 scans in graduated shades of blue (see
Figure 2-3). The current returns (i.e., the yellow) overwrite any prior returns (i.e., the blue) on
the screen. Thus, the radar displays stationary targets such as buildings and trees in yellow, the
current position of moving targets in yellow, and the previous positions of moving targets in
dimmer shades of blue. Figure 2-3 displays this effect seen quite clearly, with the target that is
east-northeast of the radar, moving in an east-southeast direction. The faint red circle (added
after the image was captured) highlights the current position (yellow blob) of the target (in this
case, a flock of Mallards), while a straight line of blue blobs denoting returns from the target’s
prior positions trails off behind it. Other, shorter target trails (faint red circles) can also be seen in
this image. [Note: This image was recorded at NAS Whidbey Island (NASWI), WA. The two
sets of faint parallel blue lines were also added after the image was captured to delineate the
positions of the NASWI runways.]
The target trails display in Figure 2-3 is not true tracking: The radar processor has no
information to connect one blob on the screen to another. The processor is simply displaying a
color-coded history of radar returns that provides the human observer with the visual cues to
“connect-the-blobs”, as it were, and more readily recognize moving targets.
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