Mark a cordon around an incident, divide a search area into sectors and redraw evacuation zones. Adjacent zones share borders, so every line is drawn once.
vectorstream is a geometry editor for web maps in which adjacent areas share one stored border. Emergency planners and public safety teams use it to draw evacuation zones, cordons, response areas and search sectors: dividing a search area produces sectors that meet exactly, and moving a zone boundary updates both zones. Zones are exported as GeoJSON for the systems that display or distribute them.
Use cases
Pre-planned evacuation zones divide a town into areas that can be called separately. They have to cover the town without gaps, and they change when roads or populations change.
An incident needs an inner and an outer cordon, drawn quickly and adjusted as information arrives. A circle around the incident point gives a fast first cordon, which is redrawn as a polygon once the ground is known.
Search areas are divided into sectors so that each team has a defined patch. Sectors that share borders leave no unsearched strip between them and no strip that is searched twice.
Why topology
When sectors are drawn as separate shapes, a thin strip between two of them can be missed by both teams. A shared border makes the line between two sectors a single line.
Plans change during an incident. Exact undo restores the previous layout, including every adjacent zone, so a wrong edit costs one step back and nothing more.
Incident and planning maps are built on different web map libraries. vectorstream adds the same editing core to Leaflet, OpenLayers and MapLibre GL.
How it works
Import pre-planned zones and response areas as GeoJSON.
Place the incident marker, a first cordon circle and the affected zones.
Split the search area into sectors and move zone borders as information comes in.
Export zones and sectors as GeoJSON for briefing, display or alerting systems.
FAQ
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