Walkthrough — Isochrone

Promise: redraw a parcel's boundary in QGIS → Ctrl+S → its accessibility rings are recomputed from the new centroid. No GIS-client plugin needed.

What you'll see

When a parcel's geometry moves (merge, split, cadastral correction), its walking isochrones must follow. This rule recomputes the 3 concentric rings via the OSM road network on every parcel save.

Before	After save
Rings frozen on the old parcel centroid	3 isochrone polygons recomputed from the new centroid

Prerequisites

• QGIS ≥ 3.28
• gispulse ≥ 1.5.1 (pipx install gispulse)
• The demo pack: gispulse examples fetch isochrone

Setup (~1 min)

gispulse track install ~/.gispulse/examples/isochrone/parcels.gpkg

gispulse triggers watch \
  --rules ~/.gispulse/examples/isochrone/triggers.yaml \
  --dataset ~/.gispulse/examples/isochrone/parcels.gpkg

The rule uses the road network bundled with the demo pack (network.gpkg under ~/.gispulse/examples/isochrone/) — no OSRM or Valhalla calls, everything stays local.

The scenario in 3 steps

1. Pick a parcel to edit

Open parcels and isochrones side by side in QGIS. Pick a parcel near a ring boundary — the visual effect will be more striking.

2. Redraw its boundary

Toggle edit mode (Ctrl+E), nudge a few vertices to shift the centroid by tens of meters, then save (Ctrl+S).

3. The trigger re-isochrones

The terminal shows:

[info] dml.changed parcels fid=87
[info] rule:recompute_isochrones triggered
[info]   → 3 rings recomputed (500m, 750m, 1000m)
[info]   → routing graph cache hit
[info] commit ok in 312 ms

Refresh the isochrones layer in QGIS (F5) — the 3 polygons follow the new parcel centroid.

See the same scenario online

🔗 Try it on try.gispulse.dev/isochrone

In the portal you can drag-drop the parcel boundary directly on the map. The rule runs in dryrun mode (actions are captured but not committed) so you see the result without touching the demo dataset.

Expected portal output

Events panel (/explorer):

2026-05-02T14:32:11Z  recompute_isochrones  parcels#87  ok 312ms
2026-05-02T14:32:11Z  dml.changed           parcels    fid=87

Map panel: the 3 rings reshape live as you drag the parcel.

Cost and limits

• In-memory routing graph cache: the first recompute after startup takes ~800 ms; subsequent ones ~300 ms.
• gispulse triggers watch ceiling: 50 triggers per second — plenty for the demo (manual edits).
• For batches >1k modified parcels, prefer gispulse triggers run --once --bulk-threshold 100, which disables watch and runs vectorised in one pass.

What's next?

• Parcels shows the inverse effect: reclassifying a parcel's buildings when the parcel itself changes.
• Audit traces every recompute for later review.
• The CLI ↔ Portal matrix lists every entry point available on both sides.