Vaisala IRIS - DWELL Algorithm: Composite in Time; Figure 48 DWELL Schematic Example

It is recommended that the Max Time Span be set to just under the skip time. Using a skip
time is generally required if you are compositing radars with dierent times between volume
scans.
5.3 DWELL Algorithm: Composite in
Time
DWELL is comprised of a product and composites successive images of a product in time.
Moving targets show a "streak" on the display.
DWELL is similar to the photographic technique of leaving the camera shutter open while
photographing a moving target. The background is fixed and the moving target shows a
"blur" behind it.
t–2
t–1
t0
Input Product Sequence
Dwell Product at Time t0
Figure 48 DWELL Schematic Example
The DWELL product algorithm is a "time composite" of the input products. Because of this,
the product that is generated by the DWELL algorithm is of the same type as the input
product. For example, if we "dwell" a PPI product, a new PPI product is generated. The
choices for the type of data that are displayed in the DWELL PPI product are:
• Original input data
For example, if a PPI of dBZ is used as input, then DWELL makes a time composite of
dBZ.
This is useful for showing where precipitation has fallen during the dwell time. When
animated, the life cycle of growth, decay and motion of individual echoes can be easily
seen.
• Time
The data points in the DWELL product are coded by their age from the time of the most
recent product in the DWELL. The display shows a color coded time history of echoes.
Chapter 5 – Configuring and Scheduling Optional IRIS Products
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