The first version of Augur only supported circles. Pick a lat/lon and a radius in km. It works fine for refineries, wellheads, single buildings — anything that's roughly circular and smaller than 25km across.
But three different customer interviews independently asked for polygons in the first month: a freight forwarder watching the Port of Rotterdam (basin shape, not a circle), a wire-service newsroom watching the Israel–Gaza border (linear corridor) and an energy operator monitoring the entire Niger Delta (huge, irregular shape).
When circles win
- Single fixed asset (refinery, transformer, wellhead).
- You want to expand the radius cheaply during a crisis.
- You don't care about false-positives at the edges.
- You want the simplest possible UI for non-technical users.
When polygons win
- Port basins — the bay isn't round, neither is your alerting need.
- National borders — the country's shape is the zone.
- Pipeline / cable corridors — long thin polygons hug the route.
- City districts — you care about CBD events, not suburb traffic.
How matching works
Circles use haversine distance — under 200μs per event/zone comparison. Polygons use ray-cast point-in-polygon — under 400μs per event/zone comparison. For typical customer load (hundreds of zones, thousands of events per dispatch cycle) the difference is unmeasurable.
You can mix both shapes on the same account, snooze either, export-import either, and embed either. Pick whichever fits the asset. Don't over-think it.