A radar reports rain as a distance and a direction from itself. It does not know that villages, streams or gauges exist. Switch the layers below to see what it knows alone and what has to be added by a survey.
| Site | Type | Bearing | Distance | Radar view |
|---|
The radar does not produce this table. It comes from the survey: "the village is in this direction, this far away". Click a row for its data sources.
Every value in the system and where it comes from. Click a row for how it is obtained and what breaks without it.
| Item | Source | What it is | Why it matters |
|---|
What the radar gives you automatically, what it can never give you, and what fills each gap.
| WR2120 | WR110 | |
|---|---|---|
| Type | Dual-polarization | Single-polarization |
| Fields | DBZH, VRADH, WRADH, ZDR, KDP, PHIDP, RHOHV, RATE | DBZH, VRADH, WRADH, RATE |
| Rain from | KDP where above 0.3, otherwise corrected reflectivity | Raw reflectivity |
| Attenuation | Corrected using phase | Not corrected |
| In this replay | Reaches warning at about 08:50 PKT | Heavy rain weakens the signal; capped near 75 mm/h and never reaches radar warning |
A gauge on a stream 25 km north of the radar is outside the 20 km coverage. It can still send water levels by telemetry, because the gauge does not depend on the radar.
The radar would not see the rain falling on that gauge's catchment beyond 20 km, so the warning has no rain lead time from that area. The survey needs to record the bearing and distance so this gap is known.
What has to be gathered when a radar is installed. Marked fields are in this demo only as approximate values. The rest are not collected and would be needed before going live.