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# Initial plan

## Scope

Turn a GNSS fix plus a destination into guidance on the bus. Nothing about
rendering — that belongs to the display client.

## Order

1. Confirm Valhalla builds and runs on the Jetson (arm64). This is the one real
   integration risk in the whole navigation workstream — upstream's arm64
   container story is unsettled. Do it before anything else.
2. Stand up Valhalla against artifacts from `tool-mapmint`, serving HTTP locally.
3. Define the routing provider interface, with Valhalla as the first implementation.
4. Bridge: subscribe to `yukart/gnss/fix`, publish `yukart/nav/guidance`.
5. Meili map matching over recorded sessions — see below.

## Why map matching comes early

Meili's `trace_attributes` snaps a recorded GNSS trace onto OSM and returns road
attribution along it: speed limit, road class, geometry. That is ground truth for
validating reverse-engineered CAN signals, which is otherwise guesswork. It is
worth having before any navigation UI exists.

## Blocked on

Live guidance needs a GNSS fix, which needs gpsd, which needs the SIM7600 brought
up in [orin-nano-env-setup](gitea:yukart/orin-nano-env-setup). Everything else here
can be built and validated against a replayed trace.