Target Detection: Input Task and Product Optimization

60 ... 100 km (37.3 ... 62.1 mi).

The maximum range of detection depends on the performance characteristics of the radar.

Typically about 60 km (37.3 mi) detection range can be expected for a 1 to 1.5° beam width antenna.

For example, 125 meters (410 ft 1 in).

This depends on the processor performance characteristics.

On magnetron systems, SQI thresholding of the dBZ may be used instead of this.

This discards non-coherent targets such as 2nd trip echoes.

The value depends on the radar phase stability performance characteristics but is typically be in the range 10 ... 20 dB.

The goal is to eliminate strong clutter targets which could produce false alarms.

Adjusted higher than usual. For example, approximately 0.45

This is to eliminate velocity speckles which could produce false alarms.

Adjusted higher than usual for weather.

This is to eliminate speckles in intensity which could produce false alarms.

Few elevation angles covering only the heights of interest to a range of approximately 60 km (37.3 mi). This allows more rapid updates.

For example, for a 1° antenna beam, the 5 elevation angles of 0.5, 1.5, 2.5, 3.5, 4.5 would provide continuous vertical coverage up to 2 km (1.2 mi), from 25 ... 60 km (15.5 ... 37.3 mi). At 10 km (6.2 mi) the coverage would be to above the radar.

Moderately fast scan rate (>3 RPM) consistent with rapid updates, but still allowing approximately 50 pulses per antenna beam width.

For example a PRF of 1000 Hz and a scan rate of 3 RPM (18 degrees per second) would provide 1000/18=55 pulses for each degree of antenna motion.

PPI

dBZ or radial velocity at single or multiple sweeps.

Radial velocity is recommended for discriminating between airborne targets and background clear air or weak weather echoes.

Airborne targets, such as aircraft or birds, move at a different velocity than the air so that, provided the targets are stronger targets, they produce a velocity anomaly which can be passed by the contrasting algorithm.

If the motion of the target is perpendicular to the radar beam, the clutter filtering can remove targets so there is a possibility of some "blind" sectors because of this.

VIL

Covering the layer of interest.

VIL is a useful product for target warning since it integrates echo over a selected layer.

Single PPI products can be used, but since they are at only one elevation angle, not all heights are covered. However, a PPI product made with the wild card * in the elevation selection can be used to combine together all the PPI products in a volume regardless of the elevation angle.

In this case, the DWELL algorithm runs at the completion of every sweep, and since the algorithm is intensive, the system may not have enough CPU power to do all of the DWELL products plus the other functions (for example, user display, animation, other product generation, communication). The DWELL product generation would then fall behind real time.

Therefore if all of the PPI products are used, it is recommended that the DWELL product schedule entry use the Skip Time in Product Scheduler, set to the time between volume scans. Thus a new DWELL product is produced on the completion of the volume scan rather than on completion of each individual PPI.

Set so that the resolution of the original input data is preserved.

For example, for 125-m (410 ft 1 in) bin spacing to 45 km (28.0 mi), the product pixel size should be set to 720 × 720 (corresponding to 90 km (55.9 mi) diameter and 0.125 m (5 in) per pixel).