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The roadbook rides itself

· 3 min read
Massimo Di Stefano
Massimo Di Stefano
FastGIS author

Since July the rider app has been able to turn any track into a rally-style tulip roadbook — the Rally side of the Road ⇄ Rally toggle reads the corners straight off the GPX shape, no road network required. It was a document: something to scroll with a thumb at a fuel stop. Today it becomes a navigation mode.

Ride, not read​

Open any track's roadbook, flip it to Rally, and there is now a Ride button. It builds a turn-by-turn session from the track's geometry alone: every bend is classified by its clustered turn angle — kink, mild, sharp, elbow, hairpin — with S-bends linked into chicanes, and each one becomes a maneuver the normal navigation engine drives. Nothing is looked up. No map-matching, no tiles, no server, no signal. If the points are on the phone, the roadbook rides.

What the HUD shows​

  • A tulip glyph instead of a road arrow — the same approach-line-and-exit shape you would draw in a paper roadbook, coloured by direction.
  • Distance to the next note, counting down odometer-style along the track as you cover ground, not as the crow flies. On a stack of hairpins the "nearest note" is often three switchbacks above you; along-track distance never makes that mistake.
  • CAP, the compass heading to hold out of the bend — CAP 135° SE — the rally navigator's oldest trick for confirming you left a junction the right way.
  • Danger chips: !, !!, !!! from radius, blindness and downhill grade.

Spoken cues follow suit — "hairpin left, 160", "S-bends" — in the navigation voice language you already chose.

What it deliberately does not do​

A roadbook ride never replans. Going off the line does not summon a router to "fix" the route (there is none to summon, and on a trail the fix is usually worse than the problem). The HUD drops to a calm following your track hint, the voice says so once, and the cues resume the moment you are back on the line. That quiet path existed in the engine for months as an anticipated case; this is the first mode to actually ride it.

An advisory corner-speed and gear suggestion (v = √(μ·g·r), with a grip coefficient you set) is in there too — off by default, and it stays off unless you turn it on in Settings → Navigation. Estimates about grip are not something an app should volunteer.

Where it stands​

Verified in the simulator with GPS playback along a real Norwegian pass — eleven hairpins, every one announced and advanced in order. The field test on the bike is still owed, and that is where the note spacing and the CAP lead time will get their real calibration.