====== Navigation & EV routing ======

The navigation layer (intended to run on the companion tablet) was validated live against a
**self-serve HERE Base Plan key**. Key findings:

  * **You do not need the commercial "Navigate" edition.** The free/self-serve **Explore** edition
    already includes **EV routing**, **real-time traffic**, and **speed-limit spans in routing**.
    Only the turnkey navigation engine / speed-limit warner / Electronic Horizon are Navigate-only —
    and we don't need those; the REST APIs cover it.
  * **The speed limit rides inside the routing call.** One routing request with the right parameters
    returns the maneuvers //and// per-road-segment speed limits and names — no separate lookups, and
    it bills as a single routing transaction.
  * **EV routing must be calibrated to the car.** HERE's generic sample models ~35–39 kWh/100km and
    roughly //doubles// the charging plan. Tuned to the Aiways U5 (~20 kWh/100km, 63 kWh, ~90 kW
    peak) a Berlin→Munich route came out at **21.4 kWh/100km, 3 stops, ~51 min charging** (vs a
    bogus 39 kWh/100km / 6 stops / 175 min from the generic params). Seed the initial charge from
    the car's live SoC over CAN; capping charge stops at ~80% keeps them in the fast part of the
    curve.
  * **Traffic-aware ETA** comes from comparing the traffic-aware duration to the free-flow baseline.

**Metering discipline:** one transaction = one route. Call **per-route or periodically — never per
GPS fix** (that is the only way to blow the free tier). Free tiers are generous (routing 5,000/mo),
and overage is negligible. An offline OSM map-matcher stays as a fallback for speed limits — see
[[speedwarning]].