During a wildfire, how long does it take to move people out of Fiskardo by road?
That was the question. It sounds like a database query, because it is one: load the road network, pick a start, run pgRouting's pgr_dijkstra, read the cost. Milliseconds of compute. One number.
The first number the twin gave me was absurd. And my instinct was to distrust the model. That instinct was correct, but for the wrong reasons. The model was not lying. My data was wrong in five ways. The sixth way was me.
This is the story of all six.
Round 1: The dead table
The routing query ran cleanly and returned plausible-looking paths. The problem: it was reading an old import table left over from an earlier iteration. The geometry looked like Kefalonia. The connectivity was garbage. The network I was querying was a ghost.
Lesson one of geospatial debugging: a query that runs is not a query that is right.
Round 2: The real network was somewhere else
The live road network lived in a
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