STEP_LENGTH_METERS

Assumed step length, in meters, used by pedestrian dead reckoning (PDR) to advance the position between discrete VPS fixes. Each detected step moves the position by this distance along the current VPS-anchored heading. Fixed stride (not adaptive); matches the online VPS source's value.

0.8 m is measurement-backed, not just inherited. Comparing dead reckoning's net displacement against the fixes' over the same interval gives an along-track error of −0.4 m, i.e. very slightly short — so this stride is right, or marginally generous to lower.

Do not recalibrate it from Σ(fix-to-fix distance) / Σ(steps). That divides straight-line displacement by a walked path, so any route with turns understates the stride: the same walker measured 0.70 m on one route and 0.60 m on another. An earlier note here recommended 0.70–0.72 on exactly that basis and was wrong; lowering the stride would have made the distance error worse. Only the net-to-net (along-track) comparison is curvature-free.

An adaptive cadence-dependent step length would still be better than any constant, since stride grows with walking speed — deferred, see VPS_LOCAL_PLAN.md.

Note the interaction with RESCAN_DISTANCE_METERS: the rescan gate is evaluated as steps × STEP_LENGTH_METERS, so a mis-set stride also shifts when that threshold trips relative to its value in real metres.