A new routing engine, faster and finer

Behind every route lies a heavy computation: thousands of positions, at each step, for each heading and each model. A finer search finds the gap between two islands or the shift worth tacking on, but it made you wait, all the more with every model added.

Saily WR rewrote its routing engine from scratch, keeping the same isochrone method and checking that it finds the same routes, but running several times faster. That headroom went straight into the routes: they now explore a finer grid, and every model of a request is computed at once rather than one after the other.

A day sail and an ocean crossing do not call for the same search, and few sailors want to tune a time step. So the computation now sets it from the passage's length, from a minute between two isochrones for a short coastal race to six hours for an ocean crossing: each passage gets a search to its scale, fine along the coast, quick across the ocean, with nothing to set.

Say you plan a Channel crossing in a breeze forecast to veer during the night. With a step to its scale, the route can tack on the shift at the right hour rather than an hour late. And with every model computed together, trying a departure at dusk, then another at midnight, is quick enough to compare both before choosing: you pick the hour to leave from the routes, not from a hunch.

The search still has its grain. A route stops once it is within a step's sailing of the destination: on an ocean crossing with a six-hour step, it ends up to thirty miles out, and its arrival is good to a few hours, not to the minute. For the last miles, compute again from a point closer in: a shorter passage gets a shorter step, and a finer arrival.