9. In Dwell Output, select one of the following:
• Data
The DWELL algorithm produces a time composite product in the same units as the
input products.
In the example, a PPI of dBZ would be produced.
• Time
The DWELL algorithm produces a product that shows the age of each point relative
to the most recent input product.
This display makes it easy to spot moving targets since they leave a streak of colors
ranging from the oldest to the most recent.
For examples, see Composite Algorithm (page 130).
More information
‣
Configuring DWELL Products with Target Detection Enabled (page 155)
5.3.4
DWELL Target Detection Algorithm
The target detection algorithm uses a series of motion vectors, spanning the possible range
of target speed and direction, to shift a time DWELL product.
Targets whose motion matches the assumed motion vector "pile". The depth of the pile
provides a measure of the "coherent motion" of the target. Essentially this is an
autocorrelation approach. The steps are:
1. A time DWELL product is made in the usual manner.
Note that if the target warning is enabled, then even if a data DWELL product were
requested, the time DWELL would be created for the warning.
2. The time DWELL points are shifted back in horizontal space according to a trial velocity
vector.
Targets that are moving at a constant velocity are "piled" on top of each other. The
output of this step is an intermediate "pile" product which has the number of data
points that are accumulated (piled) on each pixel.
3. A warning/centroid algorithm runs using a selectable threshold for the number of "pile"
points.
The approach is the same as in WARN : Warning/Centroid Product (page 99).
Note that the pile product units are 4X the actual number of points. For example, for a
pile of 3 points, the representation would be 12 in the diagnostic pile product (PIL).
4. The previous 2 steps are repeated for each trial.
5. After all trials have run, the centroid products for each trial are combined to eliminate
"double hits" that occur for the same flock. That is, there may be several trial winds that
produce centroids of sucient intensity (pile number).
The combination combines all centroids that are within 3 km of each other by choosing
the one with the largest pile number.
6. The combined warning product is checked for protected areas that have been hit.
7. The final output WARN product is named using the same name assigned to the DWELL
product.
Chapter 5 – Configuring and Scheduling Optional IRIS Products
RESTRICTED 151
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